final report phase 1 literature review evaluation€¦ · literature and other information sources...

Final Report

Prepared forUpper Santa Clara RiverAgricultural Technical

Working Group

Prepared by

Upper Santa Clara River Chloride TMDL Collaborative Process

Literature Review Evaluation

Ph

ase 1

September 2005

RDD/052720001 (NLH2977.DOC) I

Executive Summary

Background

On May 6, 2004, the Los Angeles Regional Water Quality Control Board (LA Board) adopted an amendment to the Water Quality Control Plan for the Los Angeles Region to revise the interim waste-load allocations and Implementation Plan of the Upper Santa Clara River (SCR) Total Maximum Daily Load. The Implementation Plan incorporated four major studies, including an evaluation of the appropriate chloride (Cl) threshold for the reasonable protection of salt-sensitive agriculture. The Los Angeles County Sanitation Districts (Districts) and the LA Board are working jointly on these studies. This compilation document contains all reports and information sources from the first (reasonable protection of salt-sensitive agriculture) of the four studies. Within the reaches of the Upper SCR, avocado, strawberry, and some nursery crops have been identified as the most Cl- and salt-sensitive crops that are currently grown or that are likely to be grown in the future.

Literature Review Evaluation Compilation Document Format

This Literature Review Evaluation compilation document brings together four individual reports and one compact disc of all literature sources. The following reports and compact disc are contained in this compilation document:

Final Literature Evaluation and Recommendations Report – This report was developed in September 2005, following feedback from the Agricultural Technical Advisory Panel (AGTAP), the Agricultural Technical Working Group (AGTWG), and other interested stakeholders.

Critical Review Report – This report was developed in September 2005, solely by the AGTAP as a comprehensive and critical review of the Literature Evaluation and Recommendations Report.

Comments and Responses to the Literature Evaluation and Recommendations Report – This report was developed in June 2005, as a summary document to compile all comments and associated responses to the Draft Literature Evaluation and Recommendations Report.

Literature Review and Evaluation Methodology Report – This report was developed in March 2005, as an initial summary of the pertinent literature and to provide a methodology for numerically evaluating literature and other information sources based on scope, applicability, and quality.

Literature Sources on Compact Disc – This enclosed CD contains all referenced literature and other information sources used for the development of the Final Literature Evaluation and Recommendations Report, as well as other general literature and information.

The four reports are presented in this compilation document as listed above, in reverse chronological order of development.

Contents

RDD/052720001 (NLH2977.DOC) III

Executive Summary

Literature Evaluation and Recommendations

Critical Review Report

Comments and Responses to the Literature Evaluation and Recommendations

Literature Review and Evaluation Methodology

Literature Sources on Compact Disc

Final Report

Prepared forUpper Santa Clara RiverAgricultural Technical

Working Group

Prepared by

Upper Santa Clara River Chloride TMDL Collaborative Process


Ph

ase 1

September 2005

Fina l Re por t


Upper Santa Clara River Chloride TMDL Collaborative

Process

Prepared for

Upper Santa Clara River Agricultural Technical Working Group

September 2005

2525 Airpark Drive Redding, California 96001

RDD\050590004 (CLR2820.DOC) III

Executive Summary

Background

On May 6, 2004, the Los Angeles Regional Water Quality Control Board (Board) adopted an amendment to the Water Quality Control Plan for the Los Angeles Region to revise the interim waste-load allocations and Implementation Plan of the Upper Santa Clara River (SCR) Total Maximum Daily Load. The Implementation Plan incorporated four major studies, including an evaluation of the appropriate chloride (Cl) threshold for the reasonable protection of salt-sensitive agriculture. The Los Angeles County Sanitation Districts (Districts) and the Board are working jointly on these studies. The Districts own and operate two water reclamation plants (the Valencia and the Saugus Water Reclamation Plants) in Los Angeles County that discharge tertiary-treated effluent to the Upper SCR. This report references both the Santa Clara River and the project study area/areas of concern as the “Upper SCR.” Within the reaches of the river, avocado, strawberry, and some nursery crops have been identified as the most Cl- and salt-sensitive crops that are currently grown and that are likely to be grown in the future.

Purpose

This report focuses on the Cl effects on these three crop types, and many other factors related to Cl effects, such as salinity, ion interactions, and management through a compre-hensive literature evaluation. As part of Phase 1, Literature Review and Evaluation Task 1 efforts, approximately 200 articles were acquired and reviewed. This report, presenting the evaluation, is the deliverable for Phase 1, Literature Review and Evaluation Task 2 efforts. It presents the criteria, methodology, and results of the evaluation used to characterize and evaluate the literature found in the literature search and review. The main objective of the evaluation is to develop a matrix that ranks each study on its usefulness in developing a Cl threshold for the reasonable protection of salt-sensitive agriculture. This report then takes that ranking, coupled with a detailed scientific evaluation of each article, and recommends (if possible) a threshold value or range for each of the three crop types of concern: avocado, strawberry, and nursery crops.

Crop Types

Avocados

Avocados are grown in several Southern California counties. According to the California Avocado Commission in 2004, the California avocado crop was valued at $380,000,000 and accounted for over 60,000 acres of producing agricultural crops. Ventura County produces the second largest avocado crop (San Diego is the largest) in California, with about 15,000 producing acres in 2003-2004. Los Angeles County reported very small acreage in 2003-2004 (135 acres) and only accounted for 0.2 percent of the California crop. Most of California avocado crops (90 percent) are Hass variety.

EXECUTIVE SUMMARY

IV RDD\050590004 (CLR2820.DOC)

The avocado is known as one of the most sensitive species among woody plants to both salinity and Cl. Because Cl is a component of a salt, it can cause osmotic stress and stress related to specific physiological effects of the Cl ion. Cl, like other salt ions, accumulates in irrigated soils in arid and semiarid regions. Because the avocado is a tropical plant that is native to regions where rainfall is frequent, avocado commercial production in semiarid regions requires irrigation. Therefore, it is likely that without adequate management, most irrigated soils on which avocados are grown eventually accumulate Cl, even where the natural levels of Cl in the soil and irrigation water are low. Irrigation management, includ-ing appropriate leaching fractions, is commonly considered necessary to avoid Cl buildup in the soil matrix.

In most cases, avocados take up Cl and transport it to the shoots and leaves. Cl is mobile in plants for the same reason that it is mobile in the soil solution – it easily moves with water and is negatively charged, similar to the exchange sites of the soil and humic matter. How-ever, when a plant transpires water from the leaf, Cl is left behind. This process is how Cl accumulates in leaves, and is why Cl accumulation in avocado leaves is directly related to transpiration. Therefore, the most distinctive symptom of Cl injury is leaf-tip burn, which is a result of high levels of Cl accumulation in leaves. Cl and/or salts can also affect other avocado growth parameters, such as root weight, trunk growth, shoot growth, yield, fruit quality, and photosynthesis.

Strawberries

California strawberry production accounts for 88 percent of the national total for fresh and frozen strawberries, and it is the seventh most valuable fruit crop grown in the state. Although the strawberry is a perennial plant, it is primarily grown as an annual in California. This partially accounts for the high yield in the state, which is over 50 percent higher than that obtained in most states. Strawberry plants are shallow rooted and, thus, sensitive to osmotic stress from soil moisture deficit.

Relative to avocados, limited research has been performed to specifically address Cl toxicity in strawberries. The research information available on strawberries and Cl was often integrated in salinity-focused studies. Most studies involved growing berries in nutrient solutions with variable salinity from added salt treatments. Results of these studies proved that salinity and Cl uptake have significant negative effects on strawberry plant growth, survivorship, and fruit production, and that there is a strong positive correlation between Cl supply and uptake. Other studies showed that Cl uptake was roughly proportional to the concentrations in soil or substrate solutions. Cl toxicity symptoms were characterized by discoloration, followed by necrosis from margins toward base of leaves, and, finally, leaf abscission.

Nursery Crops

California has the largest nursery and floral industry in the United States, responsible for approximately 22 percent of United States receipts in 2002. A vast array of nursery/ornamental crops are grown in Southern California. Irrigation and cultural methods are also diverse, including flood, drip, sprinkler, microspray, and a continuous fine mist or fog. These crops can be grown in natural soil or in containers.

EXECUTIVE SUMMARY

RDD\050590004 (CLR2820.DOC) V

Effects of elevated salt or Cl on growth of nursery crops are typically not a major concern unless visual impacts are noticed. In most cases, value of plants is determined by aesthetics rather than growth or yield. Therefore, any evidence of leaf burn, necrosis, or abscission can greatly reduce the value of the crop. Much less is known about salt tolerance and Cl injury in nursery crops relative to many agricultural crops. It is widely accepted that certain nursery crop species are the most salt- and Cl-sensitive species (e.g., azaleas, camellias, and rhododendrons). It is also widely known than most woody crops, such as many nursery species, tend to be more sensitive to Cl toxicity than herbaceous crops. Relatively few research studies are available examining Cl tolerance in nursery crops. The studies that are available vary widely in approach, objectives, and conclusions, making comparison of results among studies difficult. The appropriate threshold for Cl appears to depend greatly on the specific nursery crop and irrigation method to be used.

Evaluation

Three types of evaluation criteria were used to assess the value of the literature found during the literature review, as follows:

Scope – The study scope criteria were used to evaluate the presence or absence of valuable information. These criteria cannot be compared to any known conditions or practices; however, they indicated whether or not the literature provided valuable information on a specific aspect of the project topic. Each piece of literature was scored with a 0 or 1 for each scope of study criterion, depending on whether or not it was present in the study.

Applicability – The study applicability criteria were used to evaluate how relevant the study was to the project area in terms of environmental conditions and agricultural practices. These criteria were compared with known conditions and/or practices in the Upper SCR, and were therefore used to evaluate how applicable the literature is to the project area. Literature was given a score of 0 to 3 for each criterion, depending on the extent the criterion is examined in the literature.

Quality – The study quality criteria were used to evaluate the scientific merit of the literature. Scores of 0 to 3 were given to each piece of literature for each study quality criterion, depending on factors such as the presence or absence of standard requirements for scientific experimentation, analysis and interpretation of results, source of literature, and currency and duration of the study.

Thorough discussion is dedicated to the actual evaluation of the articles for each of the three crop types and the formulation of supporting information and trends that might or might not support establishment of a Cl threshold for these crops. The reader is encouraged to carefully review Section 3.0, Evaluation, of this report to completely understand the findings and limitations of this evaluation.

EXECUTIVE SUMMARY

VI RDD\050590004 (CLR2820.DOC)

Recommendations

Avocados

No evidence indicates that the Cl hazard level for avocados is below 100 milligrams per liter (mg/L). No scientific studies or extension specialists with experience in the project study area have indicated that Cl injury occurs below 100 mg/L. Therefore, the lower limit of the Cl hazard range is reasonably certain.

The upper range is less certain. Above this concentration (100 mg/L), the Cl hazard level has been interpreted up to 178 mg/L by at least one author. There are various reasons to believe that this upper limit is too high. The reader is referred to Section 4.0, Recom-mendations, of this report for detailed justification and discussion on this topic. At Cl concentrations between 120 and 178 mg/L, Cl injury has been demonstrated to occur in several studies. For this reason, the recommendations for the Cl thresholds that are above 100 mg/L converge on approximately 120 mg/L. The applicability of this value has some limitations because it is derived from sources that are not specific to the project study area; however, no valuable evidence suggests another proposed Cl level anywhere between 120 and 178 mg/L. Therefore, although there is clearly not enough evidence to propose an absolute threshold with the literature presently available, the best estimate of a Cl hazard concentration ranges from 100 to 120 mg/L.

Again, the reader is strongly encouraged to review the detailed information and justification of this threshold range provided in Section 4.0, Recommendations, of this report.

Strawberries

The studies that were evaluated provided valuable information about strawberry Cl uptake and correlated increased uptake with increased leaf burn. However, they did not provide sufficient data to determine an appropriate Cl threshold for irrigation water. The primary factors that lead to this conclusion are as follows:

Insufficient data were collected to correlate Cl uptake to yield and fruit-quality impacts.

The studies noted variability in plants or plant injury in control treatments, suggesting potential outside factors in the results.

Study applicability to the Upper SCR was limited primarily with respect to the following factors found in the literature:

Varieties grown Different or unknown irrigation methods Different or unknown irrigation management Different or unknown climate Different or unknown cultural practices

EXECUTIVE SUMMARY

RDD\050590004 (CLR2820.DOC) VII

Nursery Crops

The available information does not provide sufficient evidence upon which to base a recommendation for a Cl threshold for nursery crops. The primary factors that lead to this conclusion are as follows:

Studies by Wu et al., come the closest to providing the needed information, but they showed evidence of adverse effects with sprinkler irrigation at 300 mg/L Cl, suggesting that the threshold value is lower than 300 mg/L. In this case, it is difficult to justify establishing a standard based on the results of only a few experiments by one research group.

Studies by the United States Salinity Laboratory provide much information on the relative salt tolerance for soil-planted and surface-irrigated plants, but include no information on sprinkler irrigation effects. Given the importance of sprinkler irrigation to Upper SCR nursery crop production, and the differential effects of root zone as compared to foliar exposure, the value of these studies in setting an irrigation water standard is limited.

Thresholds suggested by extension pamphlets and local experts are not clearly tied to experimental data, making it difficult, again, to justify at the threshold level.

Production of nursery crops in large containers (specimen trees) is a significant component of the industry, and no data are available on Cl standards for the production of these crops.

Hundreds of plants potentially important to the industry are grown in the SCR, but data are only available on a limited number of these species.

Contents

Page

RDD\050590004 (CLR2820.DOC) IX

Executive Summary.......................................................................................................................... iii

Acronyms and Abbreviations ...................................................................................................... xiii

1.0 Introduction.........................................................................................................................1-11.1 Background .............................................................................................................1-11.2 Purpose ....................................................................................................................1-11.3 Avocados .................................................................................................................1-11.4 Strawberries.............................................................................................................1-31.5 Nursery Crops ........................................................................................................1-31.6 Works Cited.............................................................................................................1-4

2.0 Site-specific Information ..................................................................................................2-12.1 Avocado Management...........................................................................................2-1

2.1.1 Site Tours and Interviews with Avocado Growers in the Upper and Lower SCR..........................................................................................2-12.1.2 Irrigation Methods and Management ....................................................2-12.1.3 Cultural Practices ......................................................................................2-22.1.4 General Comments on Production Practices.........................................2-42.1.5 Works Cited................................................................................................2-4

2.2 Strawberry Management.......................................................................................2-52.2.1 Cultural Practices and Planting...............................................................2-52.2.2 Production Schedules ...............................................................................2-52.2.3 Irrigation Methods and Management ....................................................2-62.2.4 Irrigation Water Quality...........................................................................2-62.2.5 Soils..............................................................................................................2-62.2.6 General Observations of Strawberry Production..................................2-62.2.7 Works Cited................................................................................................2-7

2.3 Nursery Management............................................................................................2-72.3.1 Plant Species...............................................................................................2-72.3.2 Irrigation Methods ....................................................................................2-82.3.3 Irrigation Management.............................................................................2-82.3.4 Nursery Grower Concerns with Chloride and Salinity .......................2-82.3.5 Soils..............................................................................................................2-92.3.6 Distribution of Nurseries in the Area.....................................................2-92.3.7 General Observations of Nurseries.........................................................2-92.3.8 Works Cited................................................................................................2-9

3.0 Evaluation ............................................................................................................................3-13.1 Evaluation Methodology.......................................................................................3-1

3.1.1 Introduction and Purpose ........................................................................3-13.1.2 Summary ....................................................................................................3-13.1.3 Evaluation/Characterization Criteria Scoring System ........................3-3

Contents, Continued

Page

X RDD\050590004 (CLR2820.DOC)

3.2 Evaluation of Avocado Studies............................................................................ 3-73.2.1 Recommendations and Guidelines for Maximum Allowable

Chloride...................................................................................................... 3-73.2.2 The Effects of Management and Natural Variability on

Productivity and Chloride Response ................................................... 3-173.2.3 Mechanisms of Chloride Injury ............................................................ 3-223.2.4 Recommendations .................................................................................. 3-273.2.5 Works Cited ............................................................................................. 3-28

3.3 Evaluation of Strawberry Studies...................................................................... 3-323.3.1 Experimental Studies.............................................................................. 3-323.3.2 Review Publications ............................................................................... 3-343.3.3 Recommendations .................................................................................. 3-353.3.4 Works Cited ............................................................................................. 3-36

3.4 Evaluation of Nursery Crop Studies ................................................................. 3-383.4.1 Experimental Studies.............................................................................. 3-383.4.2 Review Publications ............................................................................... 3-473.4.3 Recommendations .................................................................................. 3-483.4.4 Works Cited ............................................................................................. 3-49

4.0 Surface-water-quality Evaluation and Application..................................................... 4-14.1 Introduction ............................................................................................................ 4-14.2 Approach................................................................................................................. 4-14.3 Basin Plan Objectives............................................................................................. 4-24.4 Upper Santa Clara River Sampling ..................................................................... 4-24.5 Water Reclamation Plants..................................................................................... 4-2

5.0 Summary of Recommendations for Chloride Thresholds......................................... 5-15.1 Summary of Recommendations for Avocados.................................................. 5-15.2 Summary of Recommendations for Strawberries ............................................. 5-25.3 Summary of Recommendations for Nursery Crops ......................................... 5-3

Appendices

A Field Notes B Literature Evaluation Tables C Nursery Crop Evaluation Scores D Bibliography Table

Contents, Continued

Page

RDD\050590004 (CLR2820.DOC) XI

Tables

2-1 Partial List of Nursery Species Grown in Upper SCR....................................................2-7

3-1 Summary of Evaluation Criteria by Type........................................................................3-2

3-2 Scoring System for Literature Applicability Criteria......................................................3-4

3-3 Scoring System for Study Quality Criteria ......................................................................3-5

3-4 Summary of Evaluation and Characterization Criteria .................................................3-6

3-5 Summary of Maximum Allowable Chloride Limits without Leaf Injury and/or Impacts to Yield/ Fruit Quality for Avocado...................................................3-14

3-6 Concentration Factors for Predicting Soil Salinity for Irrigation Water Salinity and the Leaching Fraction (as modified from Ayers and Westcot, 1985)..................3-20

3-7 Study Literature and Whether It Differentiated between Chloride and Sodium through Separate Analysis or Treatments.......................................................3-33

3-8 Chloride Guidelines Obtained from Review Publications ..........................................3-35

3-9 Review Publications that Provided Background Information....................................3-36

Figures

1 Surface-water-quality Study Area.....................................................................................4-3

2 Chloride Concentrations at Blue Cut Station ..................................................................4-5

3 TDS Concentrations 1 Mile Downstream from Los Angeles/Ventura County Line..........................................................................................................................4-7

4 TDS Concentrations at Saugus Water Reclamation Plant .............................................4-9

5 TDS Concentrations at Valencia Water Reclamation Plant .........................................4-11

RDD\050590004 (CLR2820.DOC) XIII

Acronyms and Abbreviations

AGTAP Agricultural Technical Advisory Panel

ANOVA analysis of variance

Ca calcium

CaCl2 calcium chloride

Cl chloride

Districts Los Angeles County Sanitation Districts

dS/m deciSiemens per meter

ECe electrical conductivity (salinity) of soil saturation extract water

ECsw electrical conductivity (salinity) of soil water

ECw electrical conductivity (salinity) of irrigation water

LA Water Board Los Angeles Regional Water Quality Control Board

LF leaching fraction

meq/L milliequivalents per liter

mg/L milligrams per liter

Na sodium

Na2SO4 sodium sulfate

NaCl sodium chloride

ppm parts per million

TDS total dissolved solids

TMDL total maximum daily load

UC University of California

UCCE University of California Cooperative Extension

Upper SCR Upper Santa Clara River and surrounding project study area

USSL United States Salinity Laboratory

WRP Water Reclamation Plant

RDD\050590004 (CLR2820.DOC) 1-1

SECTION 1.0

Introduction

1.1 Background

On May 6, 2004, the Los Angeles Regional Water Quality Control Board (LA Water Board) adopted an amendment to the Water Quality Control Plan for the Los Angeles Region to revise the interim waste-load allocations and Implementation Plan of the Upper Santa Clara River Total Maximum Daily Load (TMDL). The Implementation Plan incorporated four major studies, including an evaluation of the appropriate chloride (Cl) threshold for the reasonable protection of salt-sensitive agriculture.

This evaluation is a component of the first of the four major studies. The Los Angeles County Sanitation Districts (Districts) and LA Water Board are working jointly on these studies. The Districts own and operate two water reclamation plants (WRP) (the Valencia and the Saugus WRPs) in Los Angeles County that discharge tertiary-treated effluent to the Upper Santa Clara River (SCR). This report references both the Santa Clara River and the project study area/areas of concern as the “Upper SCR.” Within the Upper SCR, avocado, strawberry, and some nursery crops have been identified as the most salt-sensitive crops that are currently grown.

1.2 Purpose

This report focuses on Cl effects on these three crop types and many other factors related to Cl effects, such as salinity, ion interactions, and management through a comprehensive literature evaluation. As part of Phase 1, Literature Review and Evaluation Task 1 efforts, approximately 200 articles were acquired and reviewed. This report, presenting the evalu-ation, is the deliverable for Phase 1, Literature Review and Evaluation Task 2 efforts. It presents the criteria, methodology, and results of the evaluation used to characterize and evaluate the literature found in the literature search and review. The main objective of the evaluation is to develop a matrix that ranks each study on its usefulness in developing a Cl threshold for the reasonable protection of salt-sensitive agriculture.

1.3 Avocados

The avocado is a recently domesticated evergreen tree with origins in the rainforest. All avocado varieties are highly heterozygous; both egg cells and pollen grains are of unknown genetic constitution, and practically every seedling is different from all others (Kadman, 1968). This results in heterogeneous populations, meaning that avocado populations are nonuniform. Because avocados are commercially produced in climates that have greater temperature fluctuations than where they originated, climate has the largest influence on growth and production. Climatic factors, along with other environmental influences, interact in complex and incompletely understood ways to affect avocado yield.

SECTION 1.0 INTRODUCTION

1-2 RDD\050590004 (CLR2820.DOC)

The avocado is known as one of the most sensitive species among woody plants to both salinity and Cl. Because Cl is a component of a salt, it can cause osmotic stress (making it more difficult for the plant to take up water because of a change in the concentration of solutes outside the plant or plant cell) and stress related to specific physiological effects of the Cl ion. For this reason, it is difficult to determine the tolerance of avocados to Cl alone, without considering its effects as a salt. Cl, like other salt ions, accumulates in irrigated soils in arid and semiarid regions. Because the avocado is a tropical plant that is native to regions where rainfall is frequent, avocado commercial production in semiarid regions requires irrigation. Therefore, it is likely that most irrigated soils on which avocados are grown eventually accumulate Cl, even where the natural levels of Cl in the soil and irrigation water are low. Irrigation management, including appropriate leaching fractions, is commonly considered necessary to avoid Cl buildup in the soil matrix.

In most cases, avocados take up Cl and transport it to the shoots and leaves. Cl is mobile in plants for the same reason that it is mobile in the soil solution – it easily moves with water and is negatively charged, similar to the exchange sites of the soil, humic matter, and plant cell walls. Therefore, Cl follows the same path that water does in plants, from roots to leaves. However, when water transpires from the leaf, Cl is left behind. This process is how Cl accumulates in leaves, and is why Cl accumulation in avocado leaves is directly related to transpiration. Therefore, the most distinctive symptom of Cl injury is leaf-tip burn, which is a result of high levels of Cl accumulation in leaves. Cl and/or salts can also affect other avocado growth parameters, such as root weight, trunk growth, shoot growth, yield, fruit quality, and photosynthesis.

Researchers have noted that determining the salt tolerance of trees, vines, and other woody crops like avocado is complicated, because specific ion toxicities cause additional detri-mental effects. Therefore, it is extremely difficult to entirely separate the specific effects of Cl from the osmotic effects of Cl as a constituent of total salinity. Many researchers who have studied salt sensitivity in avocados have also concurrently examined Cl accumulation. In rare cases, the effects from salinity and those from Cl-specific ion toxicity can be separated out. In most cases, the distinction is not clear.

Some researchers explain that salt tolerance is characterized by the values of both the threshold at which injury occurs and the rate at which injury occurs after the threshold is passed. This relationship is referred to as the “salinity response curve or function.” This function, and the response to Cl in avocados, is influenced by the following factors:

Water quality/composition Rootstock and variety Variability within populations Growth stage and exposure duration ClimateSoils Irrigation methods, management, frequency, and leaching Cultural practices


RDD\050590004 (CLR2820.DOC) 1-3

1.4 Strawberries

California strawberry production accounts for 88 percent of the national total for fresh and frozen strawberries, and it is the seventh most valuable fruit crop grown in the state. Although the strawberry is a perennial plant, it is primarily grown as an annual in California. This partially accounts for the high yield in the state, which is over 50 percent higher than that obtained in most other states (California Strawberry Commission, 2004). Strawberry plants are shallow rooted and, thus, sensitive to osmotic stress from soil-moisture deficit. Most berries are grown with a plastic cover, which helps to increase soil warmth, decrease soil pathogen transfer, and retain soil moisture.

Little research has been done to specifically address Cl toxicity in strawberries. The research information available on strawberries and Cl is often integrated in salinity-focused studies. Most studies involve growing berries in nutrient solutions with variable salinity from added salt treatments. Results of these studies prove that salinity and Cl uptake has significant negative effects on strawberry plant growth, survivorship, and fruit production; and a strong positive correlation exists between Cl supply and uptake (Ehlig, 1961; Ehlig and Bernstein, 1958; and Guiffrida et al., 2001). Studies show that Cl uptake is proportional to the concentrations in soil or substrate solutions. Cl toxicity symptoms are characterized by discoloration, followed by necrosis from margins toward base of leaves and, finally, leaf abscission (Kepenek and Koyuncu, 2002).

Although the literature summarized is limited in scope, some Cl thresholds were suggested. The lowest irrigation-water Cl range cited in literature (Schrader and Welch, 1990) was 3 to 5 milliequivalents per liter (meq/L) (107 to 177 milligrams per liter [mg/L]). The same paper by Schrader and Welch (1990) provided a range of 5 to 7 meq/L (177 to 208 mg/L) as a soil-solution Cl threshold. The thresholds provided in this paper are guidelines and do not reference a study or secondary source of information. A lower Cl threshold for soil solution/ root uptake of 110 to 180 mg/L was provided by the Australian and New Zealand Environment and Conservation Council (1992). Differences might be because of soil type or duration and quantity of poor-quality water applied. Schrader and Welch (1990) suggested that boron can also cause injury to strawberries, and concentrations in excess of 1 mg/L in irrigation water could cause leaf burn similar to that of Cl. Specific methods or tools for growers to evaluate or calculate salinity parameters were provided, such as methodologies for determining soil extract from irrigation water electrical conductivity, strawberry yield response to salinity, and leaching fractions.

1.5 Nursery Crops

California has the largest nursery and floral industry in the United States, responsible for approximately 22 percent of United States receipts in 2002. A vast array of nursery/ornamental crops is grown in Southern California. Nursery products include potted plants and flowering foliage; bulbs, corms, roots, and tubers; flowering propagative materials; bedding plants; rose plants; woody, deciduous, and evergreen ornamentals; herbaceous perennials; turf and sod; and nursery stock other than ornamentals (Carman, 2003). Irrigation and cultural methods are also diverse, including flood, drip, sprinkler,


1-4 RDD\050590004 (CLR2820.DOC)

microspray, and a continuous fine mist or fog. These crops can be grown in natural soil or in containers.

Effects of elevated salt or Cl on nursery crop growth are typically not a major concern unless visual impacts are noticed. In most cases, value of plants is determined by aesthetics rather than growth or yield. Therefore, any evidence of leaf burn, necrosis, or abscission can greatly reduce the value of the crop. Nursery crops are generally more tolerant of surface or drip irrigation with elevated Cl than sprinkler irrigation. However, sprinkler irrigation is usually the only practical method for irrigating the commonly used 1-gallon containers. Foliar toxicity from high-Cl water can be reduced by reducing the frequency of sprinkler irrigation and avoiding applications during hot and dry parts of the day. Irrigation manage-ment and water quality at the nursery level is commonly modified to avoid foliar toxicity.

Much less is known about salt tolerance and Cl injury in nursery crops relative to many agricultural crops. It is widely accepted that certain nursery crop species are the most salt and Cl sensitive (e.g., azaleas, camellias, and rhododendrons). It is also widely known that most woody crops, such as many nursery species, tend to be more sensitive to Cl toxicity than herbaceous crops. Relatively few research studies are available examining Cl tolerance in nursery crops. Available studies vary widely in approach, objectives, and conclusions, making comparisons of results among studies difficult. The appropriate threshold for Cl appears to depend greatly on the specific nursery crop and irrigation method to be used. Plant appearance is more important than yield in nursery crops. Generally, if the growth reduction associated with applied salts (including Cl) is 50 percent or less, then the appearance of these crops is acceptable. Most studies of salt tolerance use salts containing Cl as the dominant anion. The lowest (ideal) suggested upper limit for Cl with sprinkler irrigation of nursery crops was 50 mg/L, although this was a general guideline not based on any specific research. Most general guidelines and personal communications with experts in the local nursery industry suggested approximately 3 meq/L Cl (107 mg/L Cl) as a recom-mended maximum for sprinkler irrigation. It appears that none of the general recommenda-tions was based on specific research with nursery crops important in California. Relatively recent research in California suggests that sprinkler irrigation for many nursery crops might be feasible with 300 mg/L Cl, and that drip irrigation of a somewhat larger range of species might be feasible with approximately 900 mg/L Cl.

1.6 Works Cited

Australian and New Zealand Environment and Conservation Council. 1992. Australian Water Quality Guidelines for Fresh and Marine Waters.

California Strawberry Commission. 2004. “Industry Backgrounder, California Strawberries at a Glance.” Available on Web page.

Carman, H. 2003. Urban Farmers: A Profile of the California Nursery and Floral Industry. Agricultural and Resource Economics Update, University of California Gianninni Foundation. 7(2):5-7. (Available at: http://www.agecon.ucdavis.edu/outreach/areupdatepdfs/UpdateV7N2/V7N2_2.pdf)

Ehlig, C. F. 1961. “Salt Tolerance of Strawberries under Sprinkler Irrigation.” Proceedings on Journal of American Society for Horticulture. 77:376-379.


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Ehlig, C. F. and L. Bernstein. 1958. “Salt Tolerance of Strawberries.” Proceedings on Journal of American Society for Horticulture. 72:198-206.

Guiffrida, F., C. Leonardo, and G. Noto. 2001. “Response of Soilless Grown Strawberry to Different Salinity Levels in the Nutrient Solution.” Acta Horticulturae (International Society for Horticultural Science). 559:675-680.

Kadman, A. 1968. “Selection of Avocado Rootstock Suitable for Use with Saline Irrigation Water.” California Avocado Society 1968 Yearbook. 52:145-147.

Kepenek, K. and F. Koyuncu. 2002. “Studies on the Salt Tolerance of Some Strawberry Cultivars under Glasshouse.” Acta Horticulturae (International Society for Horticultural Science). 573:297-304.

Schrader, Wayne L. and Norman C. Welch. 1990. “Salinity Management in Strawberry Production.” Strawberry News Bulletin, California Strawberry Commission. December 10.

RDD\050590004 (CLR2820.DOC) 2-1

SECTION 2.0

Site-specific Information

2.1 Avocado Management

2.1.1 Site Tours and Interviews with Avocado Growers in the Upper and Lower SCR

Site tours of avocado production operations were conducted along with interviews of growers and agronomic consultants in the SCR Valley. This area includes approximately 2 miles east of Piru, and extends westward to Saticoy. Although the Upper SCR reaches of concern are east of Piru only, it is important to obtain an overall view of all the management practices in the areas east and west of Piru, because they represent trends and influence each other. For example, Newhall Land Company explained that they manage a small test plot of avocados (0.5 acre) using the typical practices of the surrounding area. Because the test plot has only been planted for little more than a year, it is too early to determine the impacts, if any, attributable to Cl (Perez, 2005, pers. comm.). Therefore, a survey of the practices in the surrounding area was necessary to gain an understanding of the practices at Newhall Land Company.

Appendix A provides field notes of these site tours and interviews, and a summary of the findings is presented below.

2.1.2 Irrigation Methods and Management

Irrigation methods for avocados do not vary a great deal in the agricultural areas east and west of Piru in the SCR Valley. Most mature avocados are irrigated with microsprinkler systems that deliver water through spray stakes (approximately 1 foot high) that are placed at the base or near the base of each avocado tree. Sometimes, young avocado trees that are newly planted are irrigated with drip irrigation for the first 6 to 14 months after planting.

Drip irrigation is not commonly used on mature groves because of management obstacles. In most cases, the infrastructure does not exist to deliver water as frequently as is required for drip irrigation (where water is applied often in small amounts). Also, leaves and other debris that fall from avocado trees make it difficult to check if the drip system is operating correctly (Essick, 2005, pers. comm. and Nelson, 2005, pers. comm.). Although drip irrigation is used less and less frequently, it is still used by some growers (Faber, 2005, pers. comm.).

Irrigation schedules vary from grower to grower. Most growers in the area do not use specific methods, such as tensiometers that measure soil moisture, or estimates of crop water demand (evapotranspiration). Instead, irrigation scheduling is determined by convention on each farm, labor schedules, and best guesses. Commonly, irrigation systems are turned on for 12 or 24 hours (Faber, 2005, pers. comm.). In contrast, irrigation can take place every 3 to 4 days for 6 to 8 hours (Nelson, 2005, pers. comm.). Water duties vary depending on management preferences, soil conditions, water source and supply, and

SECTION 2.0 SITE-SPECIFIC INFORMATION

2-2 RDD\050590004 (CLR2820.DOC)

irrigation-system capacity. Approximately 1 acre-foot (per year) is used on young trees, whereas mature avocados are irrigated with 2 to 3 acre-feet. Greater water amounts are used in the eastern regions of the valley, and water duties closer to 2 acre-feet are used in the western regions of the valley (Lloyd-Butler, 2005, pers. comm. and Nelson, 2005, pers. comm.).

These water duties include a leaching fraction used to wash salts out of the root zone. Leaching fractions vary from 1 to 20 percent, depending on management preferences, water availability, water quality, and soil properties; however, commonly used leaching fractions are rarely above 10 percent (Nelson, 2005, pers. comm.). In contrast, Ben Faber (University of California Cooperative Extension [UCCE] Ventura County) contends that growers, for the most part, do not know what their leaching fractions are because they have good-quality water and do not purposefully apply a specific leaching fraction. However, where water quality is borderline relative to salinity, Cl, boron, and sodium (Na), growers quickly learn what their leaching fraction and optimum application timing are (Faber, 2005, pers. comm.). Leaching fractions always occur to some extent because the irrigation systems are not 100 percent efficient (Faber, 2005, pers. comm.). Irrigation occurs throughout the dry summer months; however, winter irrigation also occurs during dry winters (Faber, 2005, pers. comm.).

Poor irrigation management can contribute to leaf injury from Cl or salinity, which is commonly observed at the end of the summer growing season (August and September), or immediately before flowering in February and March. Irrigation water-quality decline at the end of the summer caused by well drawdown can also contribute to these occurrences of leaf burn. Accumulation of leaf Cl, regardless of water quality or management, is also a factor because of Cl increases in soil (Faber, 2005, pers. comm.).

2.1.3 Cultural Practices

2.1.3.1 Field Locations

Because the management required in citrus orchards precludes them from being established on sloped ground, avocado groves are typically planted on hillsides that have not been designated for citrus orchards. This type of topography often makes precise planting, management, and irrigation techniques difficult. For example, plant spacing and grids formed on level fields are often more evenly spaced than those on hillside avocado groves because of the ease of preparing nonsloping ground (Shram, 2005, pers. comm.).

2.1.3.2 Varieties and Rootstocks

The following information on varieties and rootstocks was provided by Rob Brokaw of Brokaw Nursery (2005). Hass is the only avocado variety that is commercially grown in the valley. Little production of other varieties, such as Bacon, is used for fresh-market selling, such as farmer’s markets. The most common rootstocks are Duke 7 and Thomas (Mexican-race clonals), and Toro Canyon, a hybrid between Guatemalan- and Mexican-race rootstock. Another clonal, Dusa (Merensky 2), was introduced in 2004, and promises salinity resistance, root-rot resistance, and high productivity, although it has not yet been proven commercially. Mexican or Mexican-hybrid rootstocks are used because of their cold hardiness, although they exhibit higher sensitivity to salinity than other rootstock races.


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2.1.3.3 Planting

The conventional standard spacing for avocado trees was 20 feet by 20 feet (resulting in approximately 110 trees per acre). In the past, groves were sometimes thinned to result in even wider spacing. However, grove planting is slowly becoming denser, as avocado growers experiment with spacing as close as 10 feet by 10 feet.

This trend toward smaller spacing that results in denser orchards follows similar trends in citriculture and other tree production, and is an attempt to maximize production and profits on expensive agricultural land. No thinning takes place in groves that are planted closely; however, trees need to be pruned more and, therefore, do not grow as large as trees in groves with standard spacing. Pruning the correct amount is challenging, because too much pruning results in vegetative growth that sacrifices fruit yield (Nelson, 2005, pers. comm.).

Although pruning is considered as extra labor, it is expected to be easier because the trees are smaller, and branches do not grow as large as those on larger trees. Therefore, the time and effort spent pruning is not considered to increase significantly in groves that are planted more densely. Managing smaller trees is also considered safer for laborers because they work closer to the ground (Essick, 2005, pers. comm.). Because planting and pruning are in states of change and experimentation, these practices vary widely in the SCR Valley.

Mulching is used for one of two purposes on many, but not all, avocado groves at the time of planting new trees and after planting. One purpose is to prevent root rot, caused by the fungus Phytophthora cinnamomi. Mulching promotes development of beneficial micro-organisms antagonistic to the root-rot fungus. The other purpose is to provide a beneficial growing environment for avocado roots. Mulch placed around the base of the trees encourages root growth upward where saturated soils are less likely to occur. In addition to encouraging root rot, wet soils are not conducive to avocado root growth in general. Common mulches include yard trimmings, hardwood chips, or avocado trimmings.

2.1.3.4 Pollination

Pollination is made possible by pollinator trees that are spaced either between regularly spaced Hass trees or as part of the regular spacing. These pollinator trees are usually of the Bacon or Ettinger variety. Avocados have an unusual flower that is either male in the early part of the day and female in the latter part of the day, or vice-versa. Pollinator trees have the opposite flowering habit to Hass trees, e.g., the female part of the flower opens when the male part of the flower of the Hass trees is open, or vice-versa. This enables pollination to occur by insects, mostly bees. Bees are placed in avocado groves for this purpose, and increase pollination and fruit set significantly.

2.1.3.5 Fertilizer Application

Fertilizer is usually applied through fertigation, where nutrients such as nitrogen, potassium, sulfur, and zinc are applied in solution through the irrigation system. Typically, less than 1 pound of nitrogen is applied per tree. In the Piru area, 40 to 70 pounds per acre are typical application rates for nitrogen. The most common nitrogen fertilizer is UN32 (urea). Potassium is applied as potassium sulfate (Nelson, 2005, pers. comm.).


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2.1.3.6 Pest Management

Pests requiring control in avocado culture include various diseases and insects. Prevention methods, biological control agents, and insecticides are applied only as needed. Common pests include root rot (mentioned above) and other fungal agents, bacterial agents, thrips, and mites.

2.1.3.7 Harvest and Orchard Turnover

Harvest usually begins in December and lasts through August. Typically, two to three picks of fruit take place during this time. Yields are highly variable from year to year and from grove to grove. The avocado production industry has not reached a commonly used orchard replacement interval because the industry is relatively young. However, the trend toward more frequent turnover accompanies the trend toward denser groves to maximize production (Lloyd-Butler, 2005, pers. comm. and Nelson, 2005, pers. comm.).

2.1.4 General Comments on Production Practices

As is usually the case in agriculture, economic factors drive changes in production practices. Land in the SCR Valley where avocados are grown is in the $35,000 to $45,000 per acre price range (Nelson, 2005, pers. comm. and Lloyd-Butler, 2005, pers. comm.). Also, because cultural requirements (such as contracting bees) are continually increasing in cost, growers are persistent in their efforts to maximize profits by constantly improving efficiency and production. For example, one grower reported that a 6.5-acre grove cost $60,000 to $70,000 to plant, including all field preparation (Lloyd-Butler, 2005, pers. comm.). When establish-ment costs are $10,000 per acre, the risk of growing avocados is high, and it is not sufficient to simply maintain production. Rather, production must increase continually for growers to have viable businesses.

This fact is significant for two reasons. First, it implies that the “existing conditions” or production practices are difficult to define because they are constantly changing and represent “moving targets.” Production practices are constantly changing to keep pace with new research, rising input costs, new agricultural regulations, and the inevitable consequences of monoculture, such as pest management and control. Secondly, any factor that causes even a small decrease in production, or requires a decrease in production efficiency to manage it, is considered a significant obstacle to viable avocado production.

2.1.5 Works Cited

Brokaw, Rob/Brokaw Nursery. 2005. Interview and nursery tour with Jim Jordahl/CH2M HILL. January 19.

Essick, Roger/Avocado production manager. 2005. Interview and farm tour with Stephanie Tillman/CH2M HILL and Joel Kimmelshue/CH2M HILL. February 4.

Faber, Ben/University of California Cooperative Extension. 2005. Telephone conversation with Stephanie Tillman/CH2M HILL. February 24.

Lloyd-Butler, Jim/Avocado grower. 2005. Interview and farm tour with Stephanie Tillman/CH2M HILL and Joel Kimmelshue/CH2M HILL. February 4.


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Nelson, Darrel/Fruit Growers Laboratory. 2005. Interview and farm tours with Stephanie Tillman/CH2M HILL and Joel Kimmelshue/CH2M HILL. February 3.

Perez, Chris/Newhall Land Company. 2005. Telephone conversation with Stephanie Tillman/ CH2M HILL. February 16.

Shram, Don/Avocado grower. 2005. Telephone conversation with Stephanie Tillman/CH2M HILL. January 26.

2.2 Strawberry Management

Strawberry production in the eastern part of the Upper SCR is relatively sparse. Production is typically favored by cooler temperatures found nearer to the coast than in the Upper SCR. However, strawberry production does exist in this region, and it has increased in the Camulos area in recent years (Daugovish, 2005, pers. comm.). However, the actual amount of land production is still small relative to the Oxnard plain area and was estimated at about 100 acres annually.

2.2.1 Cultural Practices and Planting

Strawberries in this region are grown on raised beds. Soils are fumigated before each planting. Fumigation products vary, but, currently, the area is using approximately 40 percent methyl bromide, about 20 percent InLineTM, and miscellaneous fumigation products for the remaining percentage. Methyl bromide is still used because of an exemption for 2005, which allows use in the area. It was noted that rising prices of methyl bromide, and regulations, would lead to discontinuation of use in the near future (Daugovish, 2005, pers. comm.). The fumigation process is typically conducted in a final planting bed preparation pass that includes application of a plastic mulch, which leaves land ready for planting after the fumigation period (Nelson, 2005, pers. comm.). The planting beds observed in the area are around 1 foot high and are typically 62 to 68 inches wide. Strawberry transplants are planted mechanically in four rows per bed.

A preplant fertilizer is usually banded in prior to fumigation. After planting, berries are fertigated through drip irrigation. Some growers conduct plant tissue analyses, but many rely on past experience and field indicators to determine fertilization schedules for various fields. Compost is not typically added to strawberry fields in this area, although it might be added in years when another crop is planted (Daugovish, 2005, pers. comm.).

2.2.2 Production Schedules

Strawberries are grown as an annual crop in this region. About 80 to 90 percent of straw-berries are planted around October and are harvested through the following summer. This planting date has been pushed earlier in recent years because growers aim to start harvest as early as possible, when strawberry prices are higher (Daugovish, 2005, pers. comm.). Another planting period sometimes occurs in late summer (around July) and is harvested through December (Nelson, 2005, pers. comm.). However, the only berry field observed in the Upper SCR appeared to be intended for planting in February or March. This field was bedded with plastic mulch but not yet punched for planting. Mr. Daugovish was surprised at this and said that the field might not have been intended for berries.


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2.2.3 Irrigation Methods and Management

Strawberries in the SCR Valley are drip irrigated, with the exception of a sprinkler-irrigated establishment period that typically lasts 4 to 6 weeks from planting. This practice is probably unnecessary and is being discouraged because of excessive runoff. The practice is also being discouraged because the majority of the surface is covered in plastic mulch, and relatively little irrigation water can infiltrate the planted zone (Daugovish, 2005, pers. comm.). The typical drip irrigation configuration includes two drip lines per bed. These lines are removed and replaced each year with new plantings. The drip emitter spacing varies, but is typically between 6 and 12 inches.

Actual irrigation requirements vary by site and soil conditions. Strawberry growers manage irrigation using climate data and evapotranspiration requirements. Some growers use California Irrigation Management Information System data and/or private weather stations to monitor weather conditions and track moisture conditions for both irrigation and disease monitoring purposes. Tensiometers are also sometimes seen in fields (Daugovish, 2005, pers. comm.). Leaching fractions are applied depending on irrigation water quality, according to the recommendations in the Integrated Pest Management for Strawberries (Division of Agricultural and Natural Resources, 1994). In general, irrigation schedules typically involve frequent, smaller applications to minimize water stress.

2.2.4 Irrigation Water Quality

The irrigation water source for all strawberry farms in the Upper SCR is from onfarm wells. Typical groundwater quality on the north side of the valley is around 45 parts per million (ppm) Cl and 1,600 ppm total dissolved solids (TDS); whereas, quality to the south and west is around 110 ppm Cl and 1,000 ppm TDS. More visible plant injury has been noted in the latter. In general, strawberry growers want TDS <1,000 ppm, Cl <100 ppm, and boron <1.0 ppm (Nelson, 2005, pers. comm.). This exemplifies potential plant injury because of Cl, but is not intended to characterize groundwater quality in an undisclosed groundwater basin in the Santa Clara River Valley.

2.2.5 Soils

It was noted that strawberries have recently been planted on heavier textures than in the past. Soils used for strawberries are typically sandy, but more clayey soils are now also being used (Nelson, 2005, pers. comm.). All soils, except those that are used for organic production, are fumigated annually. There is no known organic production in the Upper SCR.

2.2.6 General Observations of Strawberry Production

In most cases, strawberries are not widely grown in areas known to contain Cl in irrigation water exceeding typical (unimpaired) Cl levels. The UCCE has not heard of much Cl injury in strawberries and indicated that if a serious problem were occurring, they would typically have growers contacting them about any issues without much delay (Daugovish, 2005, pers. comm.).


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2.2.7 Works Cited

Daugovish, Oleg/Ventura County University of California Cooperative Extension. 2005. Telephone conversation with Mica Heilmann/CH2M HILL. February 23.

Division of Agricultural and Natural Resources. 1994. Integrated Pest Management forStrawberries. Publication 335.

Nelson, Darrell/Fruit Growers Laboratory. 2005. Personal communication with Mica Heilmann/ CH2M HILL. January 27.

2.3 Nursery Management

The nursery industry in the region is diverse, including the production of large, contain-erized, or specimen trees; smaller 1- to 5-gallon containerized material; and greenhouse and cut field flowers. The irrigation methods, irrigation management, and soil media used are also variable. This section provides a general summary of nursery management issues, grower concerns, and the geographical distribution of nurseries.

2.3.1 Plant Species

Hundreds of different nursery crops are grown in the SCR. The extent to which the industry might already avoid plant species that are not tolerant to the existing water quality is unknown. Table 2-1 presents a partial list of the nursery crops grown in the SCR.

TABLE 2-1

Partial List of Nursery Species Grown in Upper SCR

Aloe Vera Crape Myrtle Melalueca Rose

Australian Willow Euonymous Modesto Ash Sequoia

Azalea Fan Palm Mugho Pine Southern Live Oak

Bird of Paradise Ferns Nandina Star Jasmine

Bottletree Flowering Pear Nerium Oleander Sweet Gum

Bougainvillea Flowering Plum Olive Tree Sycamore

Brazilian Pepper Fruit Trees (Various) Palm (various) Tea Rose

Cactus Gardenia Pansy Viburnum

Calla Lilly Hibiscus Photinia White Alder

Camellia Iceplant Pittosporum White Birch

Camphor Juniper Pussy Willow Wisteria Tree

Coast Live Oak Liquidambar

Coast Redwood Magnolia

Flower production is also an important part of this industry. This includes cut flowers grown in greenhouses, field-grown flowers, and hydroponic flower production in greenhouses (Newman, 2005, pers. comm.).


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2.3.2 Irrigation Methods

Irrigation methods include drip (typically spitter tubes), overhead sprinklers, microspray with spray stakes, manual watering, and combinations of irrigation methods. In general, smaller containerized materials in the SCR are irrigated using sprinkler irrigation, although LaVerne Nursery operations at Piru were observed to be using drip irrigation for these smaller containers. Drip irrigation is commonly used for the production of the larger, specimen-type trees. Some operations, such as Otto & Sons Nursery near Fillmore, supple-ment drip irrigation with small volumes of sprinkler irrigation to reduce the accumulation of dust and to mitigate pest problems. Green Landscape Nursery in Saugus finds that watering large container stock (e.g., 60-inch boxes) by hand is preferable to drip irrigation because of the large volumes of water required (Green, 2005, pers. comm.).

2.3.3 Irrigation Management

Irrigation management varies widely in nursery crop production (Newman, 2005, pers. comm.). Daily irrigation of smaller containers is common for some growers. Growers of larger containerized material might irrigate every day to every other day during the summer, and as needed during the winter months depending on plant water demand and winter rainfall.

Some growers irrigate almost entirely at night, and other growers do the bulk of their irrigating during the day. In some cases, a mixed approach is used, operating automated sprinklers and drip systems at night, and irrigating plants manually during the day.

Fertigation systems are commonly, but not universally, used to supply nutrients. The use of acidification, particularly N-pHURIC (urea-sulfuric acid), appears to also be a relatively common practice. Valley Crest Nursery uses N-pHURIC to prevent the level of bicarbonates from clogging their irrigation system (O’Neill, 2005, pers. comm.). Otto & Sons Nursery felt that the use of this product is what allows them to grow the salt-sensitive plants they do. They have found that they can essentially eliminate evidence of toxic effects of their irrigation water on sensitive species by injecting the N-pHURIC.

Leaching approaches are also variable. Green Landscape Nursery applies some net leaching fraction throughout the year, but depends on winter rains to accomplish the major part of the annual leaching requirements. Valley Crest Nursery applies 120 percent of plant evapotranspiration requirements once each week to accomplish leaching of excess salts.

2.3.4 Nursery Grower Concerns with Chloride and Salinity

Managing excess hardness (especially calcium [Ca]), alkalinity, and, in some cases, boron (more difficult to leach than Cl) in their influent water appeared to be at least as important as Cl and salinity to operations of nurseries in the area. Valley Crest Nursery and Otto & Sons Nursery do not currently avoid growing any particular species because of water quality concerns. However, Green Landscape Nursery grows different species at their Newhall facility than they do at their Saugus facility because of differences in hardness and salinity in the available water.


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2.3.5 Soils

In general, growers prepare their own artificial soils for use in containers rather than natural soils. The composition of these soil mixtures is variable. Valley Crest Nursery uses a mixture of sand and wood shavings to provide the desired level of aeration and to control root-rot fungus. Green Landscape Nursery uses a mixture of sandy loam soil, horse manure, and wood shavings; but they vary the mixture according to the needs of individual plants.

2.3.6 Distribution of Nurseries in the Area

The greatest concentration of nurseries near the reaches of interest is near Fillmore, California. No existing nurseries were observed between Piru and Santa Clarita. Otto & Sons Nursery explained that the reason for the lack of nurseries in this reach is that climate is not favorable for many nursery crops; it is too hot in the summer and too cold in the winter. They noted that the easternmost nursery relative to the Fillmore area is the LaVerne Nursery operations at Piru. This apparent exception to climatic limitation is a result of locating nursery operations on the side of a hill, and even the slight increase in elevation over the valley floor makes growing the products they do more feasible (Klittich, 2005, pers. comm.). Green Landscape Nursery agreed that nursery production is probably not generally feasible between Piru and Santa Clarita because of the greater climatic extremes in this reach compared to areas west of Piru. This being said, nursery crops to a small extent have been grown here in the past and will continue to be grown here in the future.

2.3.7 General Observations of Nurseries

The following general observations were made of nursery operations in the area (these observations were not coupled with interviews with site managers):

Norman’s Nursery (northwest of Fillmore, Sycamore Road) – This nursery appeared to consist predominantly of small container stock using fixed sprinkler irrigation.

Norman’s Nursery (east of Fillmore on Highway 126, north and south sides of road) – This large operation appeared to focus on larger plants (trees), growing them in wooden boxes with drip irrigation. A large section of trees (approximately 30 to 40 acres) apparently had been washed away in the recent floods. Some smaller material was placed between the larger boxed trees with no obvious means of irrigation, suggesting these are hand-watered.

Moon Mountain Tree Farms (just east of Piru) – This nursery appeared to produce predominantly larger, boxed plant material, and to irrigate with drip irrigation. Palms and a number of other species were present.

LaVerne Nursery (northwest corner of Piru) – This nursery appeared to produce predominantly small container material using drip irrigation. It was the only nursery where drip irrigation was used for relatively small, containerized material. The nursery is located on the side of a hill, just off the floor of the valley.

2.3.8 Works Cited

Green, Richard/Green Landscape Nursery, Saugus, California. 2005. Telephone conversa-tion with Jim Jordahl/CH2M HILL. February 15.


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Klittich, Scott/Otto & Sons Nursery, Fillmore, California. 2005. Personal communication with Jim Jordahl/CH2M HILL. January 20.

Newman, Julie/University of California Cooperative Extension Horticulture, Ventura County, California. 2005. Telephone conversation with Jim Jordahl/CH2M HILL. February 14.

O’Neill, Tim/Valley Crest Tree Company – Nursery Division South, Fillmore, California. Interview with Stephanie Tillman/CH2M HILL and Joel Kimmelshue/CH2M HILL. February 4.

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SECTION 3.0

Evaluation

3.1 Evaluation Methodology

3.1.1 Introduction and Purpose

This section presents the criteria and methodology that were used to characterize and evaluate the literature found in the literature search and review. The main objective of the evaluation was to develop a matrix that ranks each study on its usefulness in developing a Cl threshold for the reasonable protection of salt-sensitive agriculture.

3.1.2 Summary

An evaluation methodology was developed such that each article from the scientific and agricultural literature that addressed Cl tolerance in one of the three crops of concern was scored. Each criterion in each category (scope, applicability, and quality) was ranked. The result for each article was a score for each criterion category, and a total score that reflected the cumulative scores in each category. This scoring methodology was developed in compliance with the Request for Proposal, which specified the development of a ranking system that could be used in a matrix to help determine articles that were useful in developing Cl threshold recommendations. The following three types of evaluation criteria were used to assess the value of the literature found during the literature review:

Scope – The study scope criteria were used to evaluate the presence or absence of valuable information. These criteria cannot be compared to any known conditions or practices; however, they indicate whether the literature provides valuable information on a specific aspect of the project topic. Each piece of literature was scored with a 0 or 1 for each scope of study criterion, depending on whether or not it was present in the study.

Applicability – The study applicability criteria were used to evaluate how relevant the study was to the Upper SCR in terms of environmental conditions and agricultural practices. These criteria were compared with known conditions and/or practices in the Upper SCR and, therefore, were used to evaluate how applicable the literature is to the Upper SCR. Literature was given a score of 0 to 3 for each criterion, depending on the extent that it was examined in the literature.

Quality – The study quality criteria were used to evaluate the scientific merit of the literature. Scores of 0 to 3 were given to each piece of literature for each study quality criterion, depending on factors such as the presence or absence of standard requirements for scientific experimentation, analysis and interpretation of results, source of literature, and currency and duration of the study.

Table 3-1 summarizes these three types of evaluation and the criteria that fall under each type.

SECTION 3.0 EVALUATION

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TABLE 3-1

Summary of Evaluation Criteria by Type

Study Scope Study Applicability Study Quality

1. Type of studya 1. Location 1. Experimental design

2. Cropa 2. Climate 2. Strength of analysis

3. Different growth stages were studied

3. Irrigation method 3. Strength of interpretation

4. Yield impacts of Cl were measured and discussed

4. Soil type 4. Strength of conclusion

5. The source of Cl was known and imposed as irrigation water treatments

5. Rootstock, variety, species, and genotype

5. Strength of implementation

6. Cl-specific ion toxic effect was discussed in relation to the results

6. Cultural practicesb 6. Study duration appropriate

for study objectives

7. Irrigation water requirement was studied and discussed

7. Irrigation management 7. Level of review

8. Osmotic effect was discussed in relation to the results

8. Routes of exposure (through surface irrigation or foliar application)

9. Physiological mechanism of Cl toxicity was studied and discussed

9. Rate of exposure (rates of Cl were applied as commercial irrigation would be applied; not increased gradually)

10. Fruit quality; for nursery crops, this refers to plant growth

11. Seasonal Cl variation (instead of constant rates)

aCrop and type of study will be noted, not scored with 0 or 1. Type of study includes lab, greenhouse, sand

cultures, common garden in field, and field scale.

bAgricultural practices will include planting techniques such as spacing and mulching, pruning, harvesting

techniques, and fertilizer use.

The Agricultural Technical Advisory Panel (AGTAP), during AGTAP Meeting No. 1 (December 2004), expressed concern that a numerical ranking system such as this one could potentially cause the dismissal of some articles with important information. The AGTAP members also indicated their unease with relying completely and totally on this type of objective ranking system, because it might neglect to include the subtleties of literature review, which ultimately depend on the best judgment of an experienced scientist.

Although no alternatives to this ranking system were offered by the AGTAP members, the project team and AGTAP members agreed that the evaluation methodology should be used as a tool to identify, organize, and rank articles, but should not be devoid of judgment based on scientific principles and experience. The reason given for this approach was that numerical rankings cannot fully reflect the importance of an article, and no evaluation system can perfectly rank articles in relation to one another.


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For this reason, all articles were ranked using the evaluation methodology; however, they were not systematically ignored if they received a low total score, nor were they systematically given more weight if they received a high total score. Although total scores were considered, scores of criterion categories were also considered.

The process of literature review depends not on evaluating scientific articles in isolation of one another, but on considering the information from them in the context of the complete literature. For example, if several articles convey similar results, even though some are based on personal experience and others are based on scientific study, then those results are given considerable weight because they are substantiated against each other. In contract, although one study might be well thought out and well documented, if it produced results that are not substantiated in several articles in the literature, it is reasonable to conclude that although those results might be correct, more research is needed to corroborate the results. In addition, some articles might score high because they are scientifically sound and applicable to the study area, but were not necessarily designed to determine a Cl threshold. Their high score shows that the information in them is useful in determining the factors that affect Cl response. Thirdly, some articles that received relatively high scores might not have been given considerable weight because of one criterion that was considered important was not met. The evaluation methodology did not account for this situation because the criteria were not weighted. Weighting the criteria was discussed, but was not considered prudent because of the complexity of the literature review process.

Therefore, the evaluation methodology served its purpose in identifying articles that are useful in developing a recommendation on a Cl threshold for the crops of concern. However, the information from a “useful” article might not contribute to the recommenda-tions a great deal if its results are not supported elsewhere in the literature. Similarly, an article might meet several criteria identified in the evaluation methodology, but contain a major flaw that was only reflected in one evaluation criterion. As mentioned above, the evaluation scoring system cannot perfectly rank articles in relation to one another, and, because of this, recommendations should not and were not based solely on the resulting values of article scores.

3.1.3 Evaluation/Characterization Criteria Scoring System

Separate scoring systems were developed for each type of evaluation criteria.

3.1.3.1 Scope Criteria Scoring System

The scope of study criteria cannot be compared to existing conditions or any standard of quality. They are either present in the study or not present. Therefore, a study received a score of 1 if the criterion was included in the study scope and a 0 if it was not. For example, literature that addresses yield impact (of Cl toxicity) received a score of 1, as did a study that addressed impact of Cl toxicity (or lack thereof) on fruit quality. A study that addressed both quality and yield impacts received a 1 in each category, giving that study a higher score than the studies that only addressed one criterion.


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3.1.3.2 Applicability Criteria Scoring System

Applicability criteria include those criteria that were used to evaluate the relevance of a study by comparing its components to existing conditions and practices, such as environ-mental conditions and cultural practices, in the Upper SCR. Unlike study scope criteria, these criteria were present in scientific literature to different degrees. The applicability criteria were considered as follows:

Absent

Present, but not representative of conditions in the Upper SCR

Present, representative of Upper SCR conditions, but not a part of the study conclusions

Present, representative of Upper SCR conditions, and a component of the study conclusions

Literature was scored on the applicability of study criteria using the methodology shown in Table 3-2.

TABLE 3-2

Scoring System for Literature Applicability Criteria

Score Description Example

0 Literature does not include information about this criteria item. Therefore, there is uncertainty of the study’s applicability (with respect to a particular criterion).

Study gives no information about rootstock.

1 Literature includes information about the criteria item that indicates the study conditions differ from the conditions of concern. Therefore, the study gives information about this criterion, which might not directly apply to current practices, but could provide valuable information on alternative practices.

Study gives information about rootstock, but the rootstock used in the study is different from rootstock used in the SCR Valley.

2 Literature includes information about the criteria item that indicates the study conditions are the same as the local conditions of concern; however, this information is not significant in the conclusions of the study or part of the study purpose and objectives. Therefore, the study is applicable with respect to this criterion, but does not provide conclusions about the relevance of this criterion.

The rootstock used in the study is used in the Upper SCR, but rootstock is not a factor in the study conclusions or stated as a part of the study purpose and objectives.

3 Literature includes information about the criteria item that indicates the study conditions are the same as the conditions of concern, and this information is significant in the conclusions of the study. Therefore, the study is applicable with respect to this criterion, and provides conclusions about its relevance to the topic of concern.

The rootstock used in the study is used in the Upper SCR, and it is a factor in the study conclusions.

3.1.3.3 Study Quality Criteria Scoring System

The scoring system for the quality of study criteria had different requirements for ranking each criterion. These are shown in Table 3-3.

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RDD\050590004 (CLR2820.DOC) 3-6

Evaluators discussed and, to the extent possible, agreed on an approach to ranking studies as objectively as possible. To ensure a high degree of standardization in the evaluations, two or more evaluators ranked randomly chosen articles in set rotation and compared results. Table 3-4 summarizes the complete evaluation and characterization criteria.

TABLE 3-4

Summary of Evaluation and Characterization Criteria

Evaluation/Characterization Criteria Scoring System

Study Scope Criteria

1. Type of Study Recorded

2. Crop Recorded

3. Growth Stage 0 or 1 (present or not present)

4. Yield Impact 0 or 1 (present or not present)

5. Source of Cl 0 or 1 (present or not present)

6. Cl-specific Ion Toxic Effect 0 or 1 (present or not present)

7. Irrigation Water Requirement 0 to 3 (degree of applicability)

8. Osmotic Effect 0 or 1 (present or not present)

9. Physical Mechanism of Cl Toxicity 0 or 1 (present or not present)

10. Fruit Quality 0 or 1 (present or not present)

11. Seasonal Cl Variation 0 to 3 (degree of applicability)

Study Applicability Criteria

1. Location 0 to 3 (degree of applicability)

2. Climate 0 to 3 (degree of applicability)

3. Irrigation Method 0 to 3 (degree of applicability)

4. Soil Type 0 to 3 (degree of applicability)

5. Rootstock, Variety, Species, and Genotype 0 to 3 (degree of applicability)

6. Cultural Practices 0 to 3 (degree of applicability)

7. Irrigation Management 0 to 3 (degree of applicability)

8. Routes of Exposure 0 to 3 (degree of applicability)

9. Rate of Exposure 0 to 3 (degree of applicability)

Study Quality Criteria

1. Experimental Design 0 to 3 (presence of essential components)

2. Strength of Analysis 0 to 3 (presence of appropriate statistical methods)

3. Strength of Interpretation 0 to 3

4. Strength of Conclusion 0 to 3

5. Strength of Implementation 0 to 3

6. Study Duration Appropriate for Study Objectives 0 to 3

7. Level of Review 0 to 3 (categories of sources of literature)

To make the comparison of literature more just, literature was separated into two categories as follows:

1. Experimental Studies (documentation of a scientific study conducted by the authors(s))

2. Review Publications (reviews of other experiments, documentation of personal experience, or other)

This distinction was made because review publications, in most cases, could not be eval-uated on the study quality criteria because most of these criteria apply to the implementa-tion of scientific studies. Therefore, the scores of the review publications were more


RDD\050590004 (CLR2820.DOC) 3-7

meaningful when they were compared to scores for other review publications, rather than when they were compared to all experimental studies and review publications.

3.2 Evaluation of Avocado Studies

The purpose for evaluating scientific literature on avocado response to Cl is to determine the maximum level of Cl in irrigation water that will allow for the reasonable protection of avocado production. The scoring system described in Section 3.1, Evaluation Methodology, was used to identify and organize important findings in the literature. Appendix B provides detailed results of this scoring system.

The literature on this subject focuses on some major themes and lacks discussion of certain aspects of the subject. The evaluation methodology served as a tool to identify these themes and information gaps, as well as a means to determine usefulness and relevance of literature to the project purpose. The scientific literature on avocado response to Cl centered on the following main related topics:

1. Recommendations and guidelines for maximum allowable Cl 2. The effects of management and natural variability on productivity and Cl response 3. Theories about the mechanisms of Cl injury

Exploring these main themes and evaluating the literature in which they were found helped determine the relevance and usefulness of the literature in determining a Cl threshold for reasonable protection of avocados. The following section discusses the evaluation of literature in the context of these three topics.

3.2.1 Recommendations and Guidelines for Maximum Allowable Chloride

3.2.1.1 Lack of Chloride Thresholds in the Literature

First, it must be noted that the literature provided no absolute thresholds, with supporting scientific evidence, that indicate a maximum concentration of Cl at which avocado trees will not grow or produce. Neither was there an absolute threshold found anywhere in the literature at which avocado injury begins, with or without yield impacts. Although specific values were recommended as maximum safe levels of Cl for avocados, these were usually associated with a management practice, such as a specific leaching fraction. Although many researchers have conducted studies and made recommendations from their results, no studies have definitively determined a threshold Cl level at which avocados are harmed.

This situation is largely because greenhouse (or controlled environment) experiments have been used to exclude other variables that might have injury or yield impacts. Results from controlled environments cannot be taken at face value because they do not represent field conditions, although they do provide clues and direction to field research. On the other hand, while field experiments provide more realistic conditions and results that might be more applicable to field production, several uncontrollable variables are always present and confound the results.

For these reasons, researchers have provided some guidelines and recommendations on avocado response to Cl, rather than suggesting absolute thresholds. These are not site specific, and are usually associated with certain conditions, such as cultural management,


3-8 RDD\050590004 (CLR2820.DOC)

irrigation practices, climate, and avocado varieties. Some researchers refer to a range of Cl concentration in which injury is possible. Others refer to a Cl hazard level, or value where Cl injury is likely to begin. Some refer to a value at which injury of specific plant tissues occurs, and others attempt to take all injury and growth parameters into consideration. The impacts on yield have generally been extrapolated from responses of other growth parameters because of the difficulty in correlating any one factor as a causal agent in yield differences.

3.2.1.2 Chloride Injury

Recommendations for the maximum permissible Cl concentration without leaf injury exist in the form of guidelines found in review publications. Results from documented scientific experiments (experimental studies) are indicative of the Cl tolerance of avocados, but might or might not be considered Cl thresholds.

Experimental Studies. A sand-culture study on avocado leaf and root response to Cl was conducted by Haas (1950b). Leaf-tip burn did not occur until the Cl concentration of the irrigation treatment reached 442 mg/L; however, the Cl was applied as calcium chloride (CaCl2). Haas (1950b) noted that Ca is beneficial in avocado nutrition, if potassium and magnesium supplies are adequate. Because the author specifically observed tip burn caused by Cl and not other types of leaf burn caused by salts in general, the high concentration at which injury occurred shows that the Ca ion might mitigate the toxic effects of Cl. (Further discussion of the effects of cations on Cl response is provided in Section 3.2.3, Mechanisms of Chloride Injury.) These results also show that the type of Cl salt introduces more variability into the question of what Cl concentration is safe for avocado growth.

The second relevant observation from this study (Haas, 1950b) is that root weight began to decline when the Cl treatment reached only 70 mg/L, which is surprisingly low, compared to other recommendations that suggest the concentration at which Cl injury might begin. These results show that although leaf burn is the most obvious and dramatic symptom of Cl injury in avocado trees, root growth inhibition might occur at an even lower Cl concen-tration than leaf damage. If this were true, thresholds determined from leaf burn might have limitations. This experiment provided valuable information into the nature of Cl toxicity and was well designed for its objectives; however, Haas (1950b) made no recommendations for a Cl threshold for leaf injury.

Ayers (1950) applied treatments of sodium chloride (NaCl), CaCl2, and sodium sulfate (Na2SO4) in culture solution to avocado plants. The lowest Cl level in the treatment solution was 408 mg/L. This Cl concentration resulted in tip burn, as did the higher treatments, but no tip burn was in the control treatment, which only contained trace amounts of Cl. Therefore, the Cl concentration that the root is exposed to at which tip burn began to occur was at or below 408 mg/L. Ayers (1950) did not propose that leaf injury necessarily occurs at this Cl concentration; the objective of the study was to study the nature of Cl and salt injury and to observe their effects. However, the study provides valuable information on the relative salt and Cl tolerance of avocados, and was one of the first studies to distinguish between Cl and Na injury.


RDD\050590004 (CLR2820.DOC) 3-9

The concentration of constituents in irrigation water can increase three-fold in the soil water, depending on soil and evapotranspiration conditions (Ayers and Westcot, 1985; Bingham et al., 1968). Therefore, these results could suggest that irrigation water with one-third of the Cl concentration in the treatments causing injury in these studies might result in Cl injury (refer to the subsequent subsection, Review Publications, for additional detail on the three-fold rule-of-thumb). However, it is not clear in these experiments if treatment application methods and growth media allowed for concentration of Cl in the root zone.

Bingham et al. (1968) conducted a study on avocado response to Cl, and were the first researchers to recommend an absolute value (rather than a range) at which a Cl hazard should be recognized. The Cl hazard is used here as a concentration at which plant injury possibly begins. The Cl hazard value derived from this study, 178 mg/L, is referred to in subsequent articles (Downton, 1978 and Gustafson et al., 1973) as an accepted threshold. However, no other studies have confirmed this threshold, and upon closer evaluation, the proposed Cl hazard is dubious because of questionable conclusions from this study, as described below.

First, the authors make the assumption that the first discernible symptom developed by trees under Cl stress is tip burn. However, the study by Haas (1950b) indicates that this is not necessarily true, because roots might be the first to respond. Results from Bernstein et al. (2004) and Wiesman (1995) (discussed in Section 3.2.3, Mechanisms of Chloride Injury) also show that roots might be affected sooner and in greater proportion than leaves under NaCl treatment. Bar et al. (1997) observed detrimental effects of Cl (not NaCl) on roots as well. Bingham et al. (1968) did not measure root response, and could not determine a threshold at which root injury occurs.

Secondly, the authors state that injury to avocado trees would be expected with a Cl con-centration of 15 to 20 meq/L (treatment levels are given in meq/L throughout the study; recommendations from the study will be converted to mg/L); however, it is unclear from the study data why this expectation was proposed. For example, leaf analysis suggested that a significant difference in leaf Cl percent occurred at the 10-meq/L Cl treatment. At this treatment, leaf Cl content was 0.48 percent. The 15-meq/L treatment was also significantly different and resulted in leaf Cl content of 0.80 percent. More important than the significant difference between treatments is the finding by Haas (1928) that normal, mature avocado leaves contained between 0.09 and 0.33 percent Cl, and tip-burned leaves contained between 0.54 and 1.21 percent Cl. Embleton et al. (1962) found that leaf Cl levels in the range of 0.25 to 0.5 percent were harmful in avocados. Bingham et al. (1968) showed that tip burn was slight at 10 meq/L, but apparently did not consider that enough injury to determine a threshold. However, if other plant tissues, such as roots, show growth inhibition before leaf injury occurs, then it is reasonable to assume that by the time leaves show tip burn, the growth of the plant is compromised. Again, because root mass was not measured, Bingham et al. (1968) had no way of determining that this was the case.

The rest of the study data, including trunk diameter, relative transpiration, and fruit harvest, are equally inconsistent with the conclusion of the study. Trunk diameter began to decline at the 5-meq/L Cl treatment, and was significantly different at the 10-meq/L Cl treatment. By the time of the 15-meq/L treatment, trunk diameter was 20 percent less than the control treatment. Relative transpiration in the 5-meq/L treatment was already 23 percent less than the control, and was 50 percent less in the 15-meq/L treatment. The


3-10 RDD\050590004 (CLR2820.DOC)

authors acknowledge that these growth parameters are highly important, so it is unclear why they were not considered in their interpretation of the study data.

Yield, although a less reliable growth parameter because it is influenced by so many factors and so variable in avocados, decreased by over 50 percent in the 15-meq/L treatment compared to the control, and decreased considerably even in the 5-meq/L treatment. The authors did not conduct statistical analysis on the yield data as they had done for the other growth parameters, and did not provide a reason (there was no discussion of yield in the results).

The authors concluded that the 15-meq/L Cl treatment represented a harmful Cl concen-tration to avocados. They reasoned that the saturation extract technique involves extracting soil with water at soil-water ratios such that the soil solution is diluted approximately three times (United States Salinity Laboratory [USSL], 1954), and proposed the maximum safe Cl concentration in soil extract was 5 meq/L, or approximately 178 mg/L. They also estimated that irrigation water constituents can concentrate three times in soil water because of evapotranspiration. Therefore, the authors concluded that 178 mg/L in irrigation water is the Cl concentration at which injury begins. However, it seems clear that injury occurred at a lower treatment level (10 meq/L instead of 15 meq/L), considering all growth parameters. Furthermore, the authors state at the end of the article that the avocado tree is sensitive to root-zone Cl in the 10- to 15-meq/L treatment. Therefore, the lower treatment is likely a better representation of the Cl hazard for avocado trees.

Using the same rule that soil solution is three times as concentrated as irrigation water, a better estimation of the Cl hazard for irrigation water from this study is 3.3 meq/L (one-third of 10 meq/L). Branson and Gustafson (1972) interpreted the results from Bingham and Fenn (1966), which documented the preliminary results for the Bingham et al. (1968) study, similarly. They concluded that Cl tip-burn injury could begin at approximately 100 mg/L Cl.

Another important aspect of this study not addressed by the authors is that the treatments with increasing amounts of Cl also had decreasing amounts of Ca, increasing amounts of magnesium, and increasing amounts of potassium. No Na salts were used. Anion adjust-ment was also carried out by decreasing sulfate and nitrate in the solutions as Cl increased. Changing proportions of cations and anions introduces variability into the experiment. Specifically, the cations used for salts can lessen Cl accumulation and its toxic effects. Nitrate has a similar effect because it substitutes for Cl uptake, and the decrease in nitrate from the control to the highest Cl treatment might have lessened the effects of Cl at lower treatment levels and worsened them at higher treatment levels. These effects are further discussed in Section 3.2.3, Mechanisms of Chloride Injury.

Although the interpretations of Bingham et al. (1968) were questionable, the study was of good quality, wide in scope, and provided valuable information.

Branson and Gustafson (1972) also reported on a study by Gustafson (although no citation was given) that indicated that tip burn on avocado leaves was prevalent in late summer if the Cl concentration of the irrigation water was higher than approximately 100 mg/L. (This statement likely refers to Gustafson [1962].) In their opinion, under the “very best of condi-tions,” the upper limit of Cl in irrigation water that should be used on avocado trees is


RDD\050590004 (CLR2820.DOC) 3-11

175 mg/L. The authors offer no reasoning or support for this value; however, it is indicative that the value where Cl injury begins, as proposed by Bingham et al. (1968), was likely too high.

Ben-Ya’acov et al. (1992) reported that over a period of 9 years, Mexican rootstock avocados yielded similarly to West Indian rootstocks when the Cl concentration in the irrigation water was less than 100 mg/L, but yielded considerably less when the irrigation water had a Cl concentration of 300 mg/L. Because of the large difference between these two Cl levels, it is impossible to interpret the Cl concentration where yield reduction began. Also, this study was conducted on Ettinger-variety avocados in Israel, and no information was provided on irrigation practices or soil type, so its applicability to the Upper SCR is limited. However, the study was included because it was an existing study that recommended a threshold, but was given a relatively low ranking (combined score of 14 points) because of its applicability to the Upper SCR.

Review Publications. As early as 1932, Thomas (1932) advised that avocados could be injured by a concentration of 100 mg/L of Cl. Conversely, the author also states that trees growing in soil with a concentration of 200 mg/L of Cl might grow well. He attributed this range to the possibility that various supplies of nitrogen in soil influence Cl uptake. Another state-ment made by this author was that Haas (no date) found avocado trees injured by irrigation water that contained 52 mg/L of Cl on poorly drained soil, although the author does not directly cite the research source. Assuming that is true, 52 mg/L of Cl in irrigation water would likely concentrate to some higher concentration in soil, especially if the soil were poorly drained.

Although Thomas’ opinions reflected his experience in Southern California, and are, therefore, likely applicable to the Upper SCR, the vagueness surrounding the suggested Cl recommendations makes it difficult to decipher if Thomas is referring to irrigation water or soil concentrations. The recommendations also do not refer specifically to injury or to yield impact. Therefore, this literature did not provide information that could be used with any certainty to develop a Cl threshold.

Trask (1960) documented his personal experience and suggested that, in general, irrigation water with more than 150 mg/L of Cl would cause varying degrees of tip burn. This recommendation would be more meaningful than that of Thomas’ because it refers to the irrigation water specifically and indicates what kind of injury occurs at that concentration. Trask also acknowledges the cumulative nature of Cl by stating that during a cycle of dry years, Cl salts might build up in soil and result in tip burn even when irrigation water has much less than 150 mg/L of Cl. He also states that irrigation water with higher Cl levels might be used with favorable conditions and leaching of salts below the root zone. These are general statements, and only indicate that the Cl “threshold” that avocado trees can withstand is variable depending on irrigation water quality and soil type. Although this information is useful, the lower limit of Trask’s Cl recommendation was not provided.

Gazit and Kadman (1976) also suggested that the Cl hazard for Mexican-rootstock avocados begins at 120 mg/L. However, their recommendations were based on experiences in Israel, and the authors did not cite specific research.


3-12 RDD\050590004 (CLR2820.DOC)

Gustafson (1976) approached the Cl hazard idea by suggesting that it begins at 100 mg/L Cl. This recommendation was based on personal field experience and did not appear to be derived from cited sources. The author stated specifically that care must be taken when water of this quality was used, but not that this concentration was where injury or yield decline necessarily occurred.

The guidelines most commonly referred to by extension publications and other review publications are from Ayers and Westcot (1985) and Mass (1990). Ayers and Westcot adapted their data from Maas (1984) and provide values for irrigation water and root-zone soil water maximum permissible Cl without leaf injury. They list 178 mg/L as the maximum Cl guideline for soil water and 117 mg/L as the maximum Cl guideline for irrigation water. The authors note that (1) maximum permissible Cl values might exceed the overall salinity tolerance of the crop, resulting in injury from both salinity and specific ion effects; and (2) the values were derived from saturation extract data assuming a 15 to 20 percent leaching fraction and total salinity of the soil extract at 1.5 times that of the total salinity of the irrigation water electrical conductivity. This latter assumption differs from that used by Bingham et al. (1968) and others who base their threshold recommendations on soil extract results that are assumed to be three times as concentrated as root-zone salinity. Bingham et al. (1968) did not mention any assumption about leaching fraction, but Ayers and Westcot (1985) presented the following explanation about the relationship among irrigation, soil, and soil extract water assuming a particular leaching fraction.

Ayers and Westcot (1985) assumed that a 15 to 20 percent leaching fraction results in an average soil-water salinity (ECsw, the average root-zone salinity to which the plant is exposed) of approximately three times that of the applied water. They also assumed that the soil extract salinity (ECe) is equal to one half that of soil water. The following scenario clarifies this terminology: If the Cl concentration of irrigation water is 100 mg/L, then the soil extract Cl concentration would be 150 mg/L, and the soil-water Cl concentration would be 300 mg/L, assuming a 15 to 20 percent leaching fraction. The soil-water Cl concentration is what roots are exposed to.

The following discussion refers to Maas (1990), because Maas (1984) uses the same data tables as Maas (1990). Maas (1990) lists only one value, for soil-water Cl, at 355 mg/L. How-ever, no notes are associated with this value regarding the concentration of salinity in soil water compared to irrigation water, nor is it associated with a leaching fraction. The author estimated soil solution Cl concentration from soil solution salinity because, he reasons, most data on salt tolerance were obtained in fields salinized with Cl salts of Na and Ca, and can be converted to express tolerances in terms of Cl concentration. He states that Cl can be estimated from electrical conductivity if Cl is the predominant anion in the soil solution, and he cites sources for avocado data such as Bernstein (1965) and Embleton et al. (1962).

Bernstein (1965) authored a U.S. Department of Agriculture bulletin on salt tolerance of fruit crops. A data table in this document shows that 3 meq/L (107 mg/L) is the limit of tolerance to Cl in saturation extract. However, no citation is provided for the data source, nor is any condition associated with these values, called Cl hazard levels by Bernstein (1965). The only information given is that the values for avocados were based on research in Weslaco, Texas. Embleton et al. (1962) published results of a mensurative study (no treatments were imposed; only measurements were made on leaves from trees in existing orchards) that measured Cl content in leaves of avocado trees of different rootstocks. Embleton et al.,


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reported that 0.25 to 0.5 percent Cl in avocado leaves was harmful; however, they made no mention of irrigation water quality with regard to salts or Cl, and indicated no Cl hazards or thresholds. Using this data, Maas (1990) interpreted that the maximum permissible Cl in soil water without leaf injury is 10 meq/L (355 mg/L). This value is consistent with the interpretation of Bingham et al. (1968) presented above.

The thresholds found in Maas (1990) were estimated and represented data generated from salt-tolerance trials, not Cl-tolerance trials. Embleton et al. (1962) did not provide saturation extract data, nor did Bernstein (1965). The data that Bernstein (1965) used might have been derived from soil saturation extracts, but the information on how that data were generated is not available, and appears to be specific to one site in Texas. Therefore, the thresholds found in Maas (1990) and Ayers and Westcot (1985) should be regarded as guidelines only, because there is uncertainty associated with the assumptions used to estimate them.

Recent recommendations from local extension agents are unchanged from those made during the early years of avocado production in Southern California. Faber (2004) advised that 100 mg/L of Cl in irrigation water is a Cl hazard level at which care must be taken in irrigation management of avocados, because injury is possible. This recommendation is the product of experiential knowledge of local UCCE agents and researchers over the last 70 years who have found no reasonable alternative to the value originally proposed. This value is used as a guideline because the extensive, long-term study (at least 10 years, because of weather, natural variability, and other site conditions) required to determine the exact threshold is difficult to fund and execute (Faber, 2005, pers. comm.).

A ranking system methodology was developed as a requirement of the scope of work (Request for Proposal). As the literature articles and other sources of information were summarized, reviewed, and interpreted, they were also ranked according to the developed ranking methodology.

The ranking system scores were used to both sort and evaluate sources of information. It is clear that the ranking system is an efficient sorting tool. The ranking system was also used as an initial evaluation tool. For example, some articles that received very low scores following summary and evaluation were only considered in a cursory sense for develop-ment of recommendations or not at all. The ability to partition the scores into scope, applicability, and quality categories also aided in the evaluation of the literature. For example, some articles only scored in one of the three categories, and this was taken into account during the evaluation process.

The ranking system alone, as an evaluation tool for the literature, was not sufficient to provide for a range of Cl concentrations recommended for irrigation. The final selection of the literature used for determining the range was developed from an iterative approach using both the numeric ranking system combined with best scientific judgment or interpretation of the literature. This resulted in the selection of literature or information sources with both high- and low-ranking scores that was based, to a significant degree, on the repeatability of the literature. This was especially true where articles might not have received a high score, yet supported the conclusions of the Cl concentration range.


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One of the most important components of developing the recommendations (or lack thereof) was the repeatability of the literature. In other words, did the literature consistently provide repeatable recommendations within a certain range of concentration?

The AGTAP, during the initial stages of review of the ranking and evaluation methodology, were united in their recommendations of using best scientific judgment or interpretation of the literature as supported by the ranking results.

Table 3-5 summarizes the maximum allowable Cl limits proposed in experimental studies and review publications.

TABLE 3-5

Summary of Maximum Allowable Chloride Limits without Leaf Injury and/or Impacts to Yield/ Fruit Quality for Avocado

Study Evaluation

Scoresa

Chloride Limit in Soil Extract

(mg/L)

Chloride Limit in Irrigation Water

(mg/L)

Chloride Limit in Soil Water

(mg/L) Notes and

Assumptions

Impacts with Respect to Yield/Fruit Quality

Bingham et al., 1968 (Experimental)

8, 13, 15, (36) 178 178 540 ECsw = 3.0 ECw

Oster & Arpaia (2002) (Evaluation of Experimental Data)

3, 19, 9, (31) -- 150; 7% yield loss for every 100 mg/L

over threshold

-- Based on production function model using yield data from long-term field studies

Impacts with Respect to Leaf Injury

University of California Committee of Consultants, 1975. Water Quality for Agriculture (Guidelines).

None None <142 <426 See Guidelines ECsw = 3.0 ECw ECsw = 3.0 ECe

Ayers (1950) (Experimental)

3, 9, 14, (26) None 136 408 ECsw = 3.0 ECw

CH2M HILL Evaluation of Bingham et al., 1968 (Evaluation of Experimental Data)

None None 118 355 ECsw = 3.0 ECe

Ayers and Westcott, 1985 (Guidelines)

3, 6, 3, (12) 178 118 355 15 to 20% LF ECsw = 2.0 ECe ECsw = 3.0 Ecw ECe = 1.5 Ecw

Based on salinity trial data converted to Cl

Trask (1960) Anecdotal Information

1, 13, 0, (14) None <150 None None

Partida (2002) Anecdotal Information

2, 15, 0, (17) None 120 to 140 annual average

None Based on avocados grown using 100% reclaimed water at Cal Poly Pomona

Gazit and Kadman (1976) Anecdotal Information

1, 0, 5, (6) None 120 None Based on avocados grown in Israel

Thomas (1932) Anecdotal Information

1, 9, 0, (10) None 100 None None

Gustafson (1976) Anecdotal Information

0, 6, 0, (6) None 100 None None

aScope, Applicability, Quality, (Total)

Notes:

ECe = electrical conductivity (salinity) of soil saturation extract water

ECw = electrical conductivity (salinity) of irrigation water

ECsw = electrical conductivity (salinity) of soil water

LF = leaching fraction


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3.2.1.3 Yield Decline

Few studies were found that measured avocado yield under various Cl concentrations. Even fewer studies correlated yield response to Cl concentrations or to other symptoms of Cl injury and proposed Cl thresholds for maximum yield. These studies were all experimental.

Bingham et al. (1968) measured yield in their sand-culture experiment on Cl response in avocados. Compared to the control treatment where no Cl was applied, yield was reduced by 54 to 75 percent in treatments ranging from 5 to 20 meq/L (178 to 710 mg/L) Cl. The authors provided no discussion or analysis of yield results, nor did there appear to be any consideration of yield in the interpretation of data to arrive at the conclusions of the study. The significance of these yield results is limited because they are derived from a sand-culture experiment and do not represent commercial field conditions, although they provide an approximate idea of the magnitude of yield decline from Cl excess. Notably, yield decline occurred in this experiment at a lower Cl treatment than the Cl concentration at which leaf burn was observed.

Ben-Ya’acov et al. (1992) observed that 9-year cumulative yields in Mexican-rootstock avocados were the same as yields from West Indian-rootstock avocados when Cl concentration was below 100 mg/L in irrigation water. When irrigation water contained 300 mg/L Cl, Mexican-rootstock avocado yields were one half that of their West Indian counterparts. Avocado varieties that are different from those used in the Upper SCR and the lack of information on site conditions and irrigation methods prevent these results from being considered as anything more than information on the magnitude of yield decline that occurs when Cl is increased by these amounts.

Montgomery Watson (1997) irrigated avocados with irrigation water of differing quality. Quality differences included, but were not limited to, variations in Cl concentration. They concluded that irrigating with reclaimed water with 262 mg/L Cl reduced avocado yield by 42 percent. Yield declined by 27 percent when irrigation water with 170 mg/L Cl was used, or when the higher Cl concentration was used with a 40 percent leaching fraction. The researchers also observed that tip burn occurred in all treatments including the control; however, leaf Cl content was not excessive (according to the guideline that 0.25 to 0.50 percent Cl represents excessive Cl causing leaf drop) in the 76-mg/L Cl treatment. This study provides the most informative results of all the literature that measured yield, because it represented 4 years of field conditions. The relevance of the conclusions is somewhat limited by other factors that likely contributed to yield differences (such as problems with irrigation systems, mite infestations, and changes in soil pH) among treatments and by the vagueness with which the authors reported their statistical results (see evaluation comments for this article in Appendix B).

Amrhein (1999) reviewed Montgomery Watson (1997) by identifying strengths and weaknesses of the project study and comparing the project results to similar results published in the scientific literature. Because multiple stresses on the trees during the course of the study made it difficult to identify one single factor that could account for the yield decline, Amrhein concluded that the results from this study should not be used to set irrigation water quality standards for Cl.

Multiple stresses that contribute to yield impacts of certain factors are characteristic of field studies, and define the purpose of why field studies are conducted. Furthermore, Amrhein


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(1999) does not suggest that field stresses such as pH, mite infestations, and errors in irriga-tion system operation affected one treatment more than another, only that the multiple stresses contributed to the reduced yield overall. This information is valuable and can only be produced from field studies, and should not necessarily be confounded with a lack of control in the experiment. For example, if high Cl levels decreased the ability of the avocado trees to overcome growth obstacles such as loss of leaves from insect infestation, then that is a component of Cl injury and should not be ignored.

Although it is true that the results from Montgomery Watson (1997) should not be con-sidered in isolation from other experimental data and experiential knowledge, they represent valuable information from a long-term field study that represented the conditions similar to commercial avocado production in the Upper SCR. No field study lacks the multiple stresses that Amrhein (1999) refers to; the design and implementation of a field study determine its relative quality and importance, rather than the naturally occurring obstacles that are beyond the experimenter’s control. However, Amrhein’s analysis is valuable in identifying the limitations of the study.

Oster and Arpaia (2002) derived coefficients for a salinity-water production function from data collected in Southern California. This function was then used to estimate the Cl contribution to yield decline for two different studies (one at a different Southern California location and one in Israel). From these three studies they found a chronic exposure threshold of 150 mg/L for irrigation water on avocados. They further concluded that a yield decline of 7 percent would accompany each additional 100 mg/L of Cl in irrigation water. This type of threshold development is applicable when data from local studies are used to validate it, but also limited because of its theoretical foundations. The authors acknowledge that the salinity-water production function underestimated the results of the studies when data were used to confirm the model, yet this does not appear to be considered in the development of a Cl threshold. Futhermore, the relative yield decline calculated from this exercise is not consistent with the yield declines found in other literature (Bingham et al., 1968; Ben-Ya’acov et al., 1992; Arpaia et al., 1996; and Montgomery Watson, 1997).

Applying a production function model requires several assumptions. This model was originally tested on crops other than avocados that likely do not have similar characteristics to the extreme salt and Cl sensitivity observed in avocados. The authors of the model point out that “the computed production functions are valid within the range of conditions that were assumed in developing the model” (Letey and Dinar, 1986). The production function specifically assumes that yields are a linear function of evapotranspiration only for the nonsaline case (i.e., the electrical conductivity of the applied water equals zero). At higher salinity levels, dependence of yields on applied water and irrigation water salinity are curvilinear. For irrigation water salinities exceeding the threshold salinity of the crop, soil salinity limits the maximum attainable yield, regardless of the amount of applied water. Limitations of the model arise when these assumptions do not apply. For example, the first condition for this model is a linear relationship between yield and evapotranspiration when the electrical conductivity of the applied irrigation water is zero. As demonstrated by several studies discussed in Section 3.2.2.1, Irrigation Management, this is likely untrue for avocados, especially when irrigation water contains excessive salinity and/or Cl.

Although the results of this exercise are interesting, estimates derived from models should always be validated with data from the specific crop and site for which the model is


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intended when exact resolutions, such as thresholds, are pursued. Therefore, this value has limited applicability in determining a safe Cl level for avocados and should not be interpreted as an absolute threshold.

3.2.1.4 Summary

The following conclusions about guidelines and recommendations for Cl can be drawn from an evaluation of the literature presented above:

1. The Cl hazard concentration of 100 mg/L proposed by UCCE agents, consultants, and researchers with experiential knowledge within and outside of the Upper SCR does not appear to be supported by data from well-documented, referenced scientific literature. However, this guideline is considered important because it has remained for over 70 years, e.g., no alternative recommendation has been proposed by others working in the field. Although this value is proposed as a minimum concentration at which avocado injury can begin, a range of Cl concentrations can be considered feasible for avocado growth with proper management. However, the literature did not explain what that type of management entails.

2. Guidelines resulting from well-documented scientific studies are limited to those of Bingham et al. (1968) and Oster and Arpaia, 2002. The recommendations of Bingham et al. (1968) were questionable because of poor interpretation of data, and are likely too high. The study conclusions did not address inhibition of growth parameters that occurred at lower treatment levels than the recommended threshold, nor did they address the type of salts used in the study. Therefore, the irrigation water Cl limit of 178 mg/L is considered beyond the concentration at which injury begins to occur. The interpretation of this study used in this evaluation and by other researchers results in a Cl hazard value of 117 mg/L, rather than 178 mg/L. The calculated Cl threshold from Oster and Arpaia (2002) was estimated from a production function model, not empirical data; and its use for this purpose is likely less applicable.

3. The guidelines recommended by often-used agricultural reference sources (Ayers and Westcot [1985] and Mass [1990]) are derived from estimations using accepted methods of estimating soil extract Cl concentration. Because they were not derived from site-specific empirical data, they should be regarded as guidelines and not absolute values, and are associated with specific leaching fractions that indicate that management can change their relevance.

4. The paucity of information on yield decline associated with Cl excess in avocados does not allow for a quantitative correlation between Cl concentrations and yield impacts.

3.2.2 The Effects of Management and Natural Variability on Productivity and Chloride Response

The evaluation of the literature on Cl recommendations for avocados presented above reveals the variation in recommended values and the range of uncertainty associated with these values. This uncertainty indicates that recommended values cannot be considered absolute values and must be considered in the context of several factors. The reason for the wide variation in recommended values and the uncertainty associated with them is two-fold.


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First, management practices, which vary from grower to grower, have a considerable effect on the level of stress avocado trees experience from a particular yield factor and how much stress avocado trees can experience before exhibiting injury or decreasing production. Management practices that directly affect Cl uptake are irrigation water quality, leaching fraction, and irrigation frequency. Management practices that affect overall tree health, such as pest management and nutrition, affect how avocado trees respond to environmental stresses and might affect Cl tolerance.

Secondly, avocado production is highly variable from avocado population to population and from year to year (Kurtz et al., 1992; Faber et al, 1995; and Faber, 2005, pers. comm.). This natural variability is present in all agricultural crops. Natural variability in avocado fruit crops results from weather conditions at critical times (such as blooming) that vary from year to year, from inherent genetic variability in avocado populations, and from the fact that the avocado plant is not native to the Upper SCR, but is rather a plant that evolved in a much different climate. The studies evaluated in the following section are all experimental studies.

3.2.2.1 Irrigation Management

Cl is a highly mobile ion in soils, and its movement is affected by convective transport of soil water and chemical diffusion (dispersion) of Cl ions. Therefore, many researchers have reasoned that water management should affect Cl availability and root uptake in irrigation crops. Several researchers have conducted experiments designed to observe the relationship between irrigation management and Cl uptake in avocados by varying irrigation rate and frequency. These studies are, in general, poorly documented or incomplete, and, as a result, inconclusive. Few studies have attempted to develop a relationship between the amount of irrigation water applied and Cl uptake. The results from these studies are often confounded by other factors that contribute to growth.

Bingham and Richards (1958) concluded that increasing irrigation frequency increased Cl levels in soil and plant tissue of avocados irrigated with water that was relatively low in salts. However, the authors provided little or no information on site conditions, experimen-tal objectives and design, or how irrigation was applied, making this conclusion less meaningful than it could have been in the context of this information.

Contrary to these results, Gustafson (1962) concluded that increasing the frequency of irrigation and therefore imposing lighter leaching fractions (more often) reduced tip burn in avocados, indicating that soil availability and uptake of Cl was lessened under these condi-tions. However, the usefulness of this article is diminished by the lack of information about the study, including avocado variety and experimental design, and the lack of discussion of some interesting data that are inconsistent with expected outcomes of the study. For example, some sites showed lower Cl levels in leaves than other sites with higher Cl levels in the irrigation water. Also, the degree of tip burn did not always increase with increasing leaf Cl content, and was also not necessarily consistent with irrigation water Cl levels. Discussion of the possible reasons for these results based on the author’s direct experience with the study would have enhanced the meaning of the study results. Gustafson (1976) concluded that the higher the Cl content in irrigation water, the more frequent the irrigation should be and the more water should be used.


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Lahav et al. (1992) observed that increasing the amount of water applied increased trunk growth, fruit yield, and fruit quality. However, it is unknown if these results were the consequences of higher water uptake, more nitrogen applied as water treatments increased, or decreased availability of Cl and/or other salts. Because nitrogen was not controlled in the irrigation water treatments, more nitrogen was applied as more water was applied. This lack of control and the brief documentation provided in this article restricted its usefulness.

In another study conducted to determine the relationship between irrigation rates and Cl and salinity accumulation in soil and leaves (Kurtz et al., 1992), the authors concluded that Cl accumulation decreased as irrigation rate increased. Although an apparent objective of the study was to determine the leaching fraction required to prevent accumulation of Cl and salts during the irrigation season, the authors do not specify the soils used in this study, which is an important factor when considering leaching fractions. Also, their interpretation of the data is questionable because they refer to a 30 percent leaching fraction (an irrigation treatment at 130 percent of evapotranspiration) as an 86 percent leaching fraction because they were comparing it the lowest irrigation treatment, and not to 100 percent evapotranspiration.

Although irrigation frequency and rate may have an effect on Cl accumulation, other growth effects of applying more or less water to avocado trees must be considered. Faber et al. (1995) reported that applying irrigation at 111 percent of evapotranspiration favored growth and sacrificed yield in avocados over a 4-year study. This observation suggest that overapplying water in an attempt to leach Cl and other salts from the root zone could have other impacts on tree growth that are not necessarily desired. These results also show that leaching fractions and frequency must be considered if more water is applied for this purpose. In other words, total management must be considered when management practices are changed to mitigate environmental stresses on crop production. The results from this study were incomplete, and no completed documentation of this study was found in the literature search.

Preliminary results from Arpaia et al. (1996), an avocado irrigation trial comparing irrigation frequency and rate treatments, showed that less frequent irrigations resulted in lower Cl leaf levels in some years. However, lower irrigation rates increased Cl accumula-tion in leaves compared to higher irrigation rates. Contrary to the results from Faber et al. (1995), increasing the irrigation rate to over 100 percent evapotranspiration continued to increase yield (in most cases over a 3-year study period). These results were not final, and no final report was found for this study.

A field study conducted on avocado trees using various qualities and rates of irrigation water also indicated that irrigation rates should be modified to reflect irrigation water quality (Montgomery Watson, 1997). In this experiment, avocado yields were higher in a 140 percent evapotranspiration treatment than in a 100 percent evapotranspiration treatment, yet soil salinity was also higher in the 140 percent evapotranspiration treatment. This latter observation is inconsistent with the theory that increased irrigation increases leaching and decreases soil salinity (and therefore Cl), thus increasing the yield potential. Soil salinity might be increased with increasing water applied because more salts are added to the soil. Lahav and Aycicegi-Lowengart (2003) stated that increasing water amount in several irrigation experiments in Israel resulted in increased concentrations in Cl because of accumulation of Cl from irrigation water (not referenced). Therefore, rates, durations, and


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irrigation frequency likely all determine the effect of increasing water applied on soil Cl. Meiri et al. (1999) measured soil salinity and Cl under various irrigation frequencies and drip system positions. They concluded that increasing frequency elevated soil Cl and salinity levels. These studies suggest that the amount of water applied is as important as the frequency of irrigation.

These studies show that irrigation management does indeed impact Cl accumulation in soils and avocado plant tissue; however, because of the lack of consistency in results from studies and the incompleteness of the articles available in the literature, it is difficult to determine exactly what that impact is. Importantly, these studies do show that growers using different irrigation frequencies and amounts might observe different responses to the same irrigation water quality.

Furthermore, irrigation management practices have not been correlated with specific amounts of Cl accumulation or tolerance. For example, there is no information correlating irrigation water quality and specific leaching rates with a safe Cl level for avocados. This information is very site specific and is held in the experience of growers. Although sources such as Ayers and Westcot (1985) might make recommendations on safe Cl levels with assumed amounts of leaching, these recommendations might not apply to certain pro-duction sites because of the limitations of soils, climate, and other conditions. Leaching in the Upper SCR is variable and unknown. As leaching fractions increase, their effectiveness decreases (20 percent is relatively effective) and might result in other adverse impacts. It is unreasonable to assume that growers are consistently using higher than 20 percent leaching fraction and significantly reducing soil Cl. An example of this is the determination of the concentration factor of irrigation water to soil water as modified from Ayers and Westcot (1985). Table 3-6 lists the concentration factors for predicting soil salinity for irrigation water salinity and the leaching fraction.

TABLE 3-6

Concentration Factors for Predicting Soil Salinity for Irrigation Water Salinity and the Leaching Fraction (as modified from Ayers and Westcot, 1985)

Leaching Fraction (%) Applied Water Needed

(% of Evapotranspiration) Concentration Factor in

Soil Water

5 105.3 6.4

10 111.1 4.2

15 117.6 3.2

20 125.0 2.6

25 133.3 2.4

30 142.9 2.0

40 166.7 1.8

50 200.0 1.6

60 250.0 1.4

70 333.3 1.2

80 500.0 1.2


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Even fewer studies have been conducted with the intent of determining if management other than irrigation practices contributes to the extent of Cl uptake; some have explored the relationship between nutrition and Cl tolerance. Studies on this relationship are discussed in Section 3.2.3, Mechanisms of Chloride Injury.

3.2.2.2 Natural Variability

A wide range of variability has been found to occur in avocado production and in avocado response to Cl stress. Numerous researchers have found that avocado production is extremely variable within and among years and tree populations. The causes of this variation might be known, such as human error in management, or unknown.

Faber et al. (1995) observed that a study with the objective of observing effects of manage-ment practices on growth and yield should be at least 4 years long to allow for the variability in growth and yield from year to year. Other researchers have documented the wide range of variability in study results, such as degree of Cl injury and Cl accumulation in plant tissues. Bergh (1967) contends that yield varies between years because of the many factors contributing to it, including weather and pollination, which are different every year. Ben-Ya’acov et al. (1992) reported that leaf injury varied strikingly among years in a study that observed avocado responses to soil stress factors.

Field studies, in particular, exhibit the large variability in yield and other responses to environmental stresses that change every year and have different effects on different trees. Montgomery Watson (1997) and Amrhein (1999) identified multiple stresses in the field study conducted by the former that helped to explain the variation in yield that resulted among years and treatments. These factors included soil amendments for pH, insect pest infestations, nutrition, and problems with irrigation systems.

Shalhevet (1999), in a review of avocado studies on water and salinity relations, concluded that a production function for the water requirement of avocados can be developed, but the spread of data is large because of differences between years, sites, rootstocks, and cultural practices.

3.2.2.3 Summary and Significance of Variability Caused by Management Practices and Natural Variation

The wide range of variability in avocado production has been observed in numerous experiments and is uncontested by researchers. Therefore, this variability must be considered as a component of avocado production, and will be difficult to eliminate from research on avocado yield responses to certain stresses, including excessive Cl. The variability in avocado response to Cl has also been documented.

The natural variability in avocado production is significant because it introduces uncertainty into study results, particularly if studies are carried out for short periods. Many avocado studies are conducted over the course of a few months or a year, and although these provide information on initial reactions of plants to imposed treatments, the overall effect of the treatments on cumulative growth and yield is unknown.

The apparent randomness of this variability decreases with more knowledge of what causes it. Therefore, researchers have attempted to discover the mechanisms that trigger responses


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to Cl in avocados. The following section presents the available literature on mechanisms of Cl injury.

3.2.3 Mechanisms of Chloride Injury

3.2.3.1 Chloride Exclusion, Transport, and Compartmentation

The ability of plants to tolerate Cl is related to one or more of three different processes. The first process is exclusion, when plant roots resist uptake of Cl stored in soil water. The second is transport, when plants relocate the Cl they have taken up to plant tissues that are the least vulnerable to Cl injury. The third is compartmentation, when Cl is stored in tissues that are vulnerable to Cl injury, but is stored within vacuoles, thereby decreasing the potential for Cl injury. Although many authors have conducted studies on Cl sensitivity in avocados and postulated on the mechanisms that cause it, few have designed studies that specifically examine the plant physiological aspects of the three processes described above. For the most part, these processes are theoretical, because so little is known about the targets of Cl toxicity in plants in general (Serrano, 2002 and Richards, 2005).

Both Kadman (1963) and Crowley et al. (2000) proposed that avocado rootstocks might be classified as excluders or includers, referring to the tendency to exclude Cl uptake, or include it and adapt to its adverse effects some other way. In other words, rootstocks either avoid taking up Cl (excluders) or cannot avoid taking it up (includers). Rootstocks might then transport Cl to the scion (the plant part grafted to rootstocks) or sequester it in root tissue. For this reason, the latter authors reason, tolerance of grafted trees to salts and specific ions is more complex than examining only leaf tissue contents of salt constituents. In the experiment conducted by Crowley et al. (2000), Duke 7 avocado rootstock (Mexican) displayed characteristics of an includer type of rootstock, as opposed to the West Indian rootstocks that excluded Cl; and, thus, the scion took up much less Cl than when grafted on the Mexican rootstock. Hass-variety avocados were grafted onto all three types of rootstock.

Other studies have confirmed that Mexican rootstocks do not have the ability to exclude Cl from root uptake, but rather transport it to the leaves (Embleton et al., 1962; Ayers, 1950; Haas, 1950b; Haas 1950c; Haas, 1928; and Kadman, 1963). Kadman and Ben-Ya’acov (1969) also proposed that Mexican rootstocks do not employ Cl exclusion as a resistance mech-anism. Therefore, their sensitivity to Cl rests in the processes of transport and compart-mentation, and these processes should be examined to determine the nature of Cl sensitivity in Mexican-rootstock avocados.

The tissues that accumulate Cl are also important in determining extent and type of injury, which might not be consistent across all avocado varieties and rootstocks. Wiesman (1995) observed that Ettinger-variety avocado trees grafted onto Mexican rootstock (Schmidt) appeared to transport more Cl to leaves than those grafted to West Indian rootstock, result-ing in different effects on root:shoot ratio. The author theorizes that Cl might not directly affect avocado growth, but might, in fact, affect growth hormones and other factors (e.g., enzymes) related to plant growth. Bar et al. (1997) also observed that high Cl reduced the total dry matter yield of the root more than that of the shoot, decreasing the root:shoot ratio.

This theory echoes that of Bernstein et al. (2004), who suggested that root tissue develop-ment under salt (NaCl) stress might also result in reduced transport of growth regulators from the root to the shoot, which might affect shoot growth and tree productivity.


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Interestingly, although Wiesman (1995) was discussing Cl and Bernstein et al. (2004) were referring to salinity, they suggested the same theory. Bernstein et al. (2004) noticed a markedly greater effect on roots than shoots when NaCl treatments were applied to produce saline conditions. This, however, was likely caused, in part, by the displacement of Ca (by Na) from the root-cell wall, causing leakage of potassium and other plant metabolites (Crowley et al., 2002).

The role of compartmentation has been identified as a mechanism used by salt-tolerant plants to avoid toxicity by specific ions; however, no specific research on this mechanism in avocados has been conducted to date.

3.2.3.2 Osmotic Stress and Specific Ion Toxicity

The two processes of transport and compartmentation are linked to plant avoidance of two types of Cl injury. Serrano (2002) defines salt stress as including both osmotic stress (caused by the increased concentration of extracellular solutes and associated turgor loss, i.e., wilting) and intracellular ion toxicity. The same author points out that the relative impor-tance of osmotic stress and ion toxicities during salt stress depends on the salt concentration and the relative capabilities of each organism for osmotic adjustment and ion transport, which might be influenced by growth conditions. In other words, one process or the other might be the limiting factor to growth in different situations. Serrano (2002) explains that salt directly affects turgor targets while it needs to be transported into the cell to reach ion toxicity targets. He theorizes that osmotic stress is counteracted by the synthesis of ions that can help the plant osmotically adjust; whereas, ion toxicity is relieved by transport systems that move the toxic ion into and out of cells or parts of cells.

Osmotic adjustment is a genetic adaptation of drought-tolerant plants that prevent them from wilting when water is unavailable for root uptake (either because of true drought or physiological drought). Plants adjust osmotic potential by increasing the amount of solutes in water inside the plant without affecting the turgor pressure that keeps leaves and other shoot tissues from wilting.

There is some evidence that the avocado plant has the ability to adjust osmotically. Gonzales-Rosas et al. (2003) studied in vitro cultures of mature avocado embryos and determined that avocados have some degree of osmotic adjustment. Bingham et al. (1968) observed that turgidity in parts of avocado leaves showing tip burn decreased by 5 percent when Cl treatment levels were increased from the control to the highest treatment level (20 meq/L [710 mg/L]); however, no decrease in turgidity occurred at the lowest treatment level where symptoms of injury began to show (10 meq/L [355 mg/L] Cl). Therefore, the results of this study suggest one of two things: (1) osmotic adjustment in avocados might have occurred at and below 10 meq/L (355 mg/L) Cl, but not above that concentration; or (2) no osmotic adjustment was necessary because leaf-water potential was not affected enough to cause osmotic stress. The authors also state that observations of xylem fluid electrical conductivity in the 20-meq/L (710-mg/L) Cl treatment suggested that an extracellular osmotic effect might be the cause of leaf injury. However, the same observa-tions were not made of the 10-meq/L (355-mg/L) treatment where injury began to occur.

Other studies show that ion toxicity is the main component of salt stress when Cl injury begins to occur in avocados. Mickelbart and Arpaia (2002) concluded that reduction in leaf


3-24 RDD\050590004 (CLR2820.DOC)

area in response to salinity observed in their study did not appear to be a result of decreased water availability. This conclusion resulted from the observation that midday leaf relative water content decreased only slightly with salinity and was not correlated with leaf area. The treatments used in this study consisted of equal molar portions of NaCl and CaCl2

ranging from 1.5 to 6.0 decisiemens per meter (dS/m).

Bar et al. (1997) also suggested that Cl injury in avocados was the result of Cl ion toxicity. Their experiment compared avocado response of nitrate salts to Cl salts. Toxic symptoms appeared only when Cl was the main anion, leading the authors to conclude that within the range of salinity and Cl concentrations used in their study, the toxic symptoms were not from osmotic effects, but rather from Cl-specific toxicity. Cl concentration in treatments ranged from 71 to 568 mg/L.

These observations present the idea that osmotic injury in avocados might indeed occur, but not until Cl levels are much higher than the concentrations at which ion-specific Cl toxicity occurs. Crowley et al. (2000) state, “If we identify rootstocks that are particularly resistant to the effects of high Cl, we will increase the salt levels to an appropriate level that will test the full extent of salt tolerance of the more tolerant selections.” This suggests that Cl effects would be apparent at lower Cl treatment levels than salt effects.

The idea that Cl-specific injury supersedes osmotic effects was also acknowledged by Greenway and Munns (1980), who state unequivocally that Cl levels causing injury in avocados, according to Downton (1978), are so low that adverse effects from low osmotic potential are implausible. These statements echo Ayers (1950), who declared that the salinity of the culture solutions used in his experiment (ranging from 0.04 to 0.19 megaPascal osmotic pressure, and trace to 1,704 mg/L Cl) was so low that it would be difficult to attribute the observed leaf injury to the osmotic factor.

Richards (2005) cites several reasons for this rationale. First, the osmotic potential of damaging Cl concentrations is very close to zero. Even at 5 meq/L (178 mg/L) Cl, osmotic potential is only –0.023 megaPascal, compared to –0.033 megaPascal, the osmotic potential of field-capacity soil with no salt. Secondly, the osmotic potential of damaging Cl concentra-tions is within water relations tolerance limits of avocados (Chartzoulakis et al., 2002). Thirdly, nitrate ions should increase damage if osmotic stress is the cause, because nitrate ions are solutes and change the osmotic potential; however, nitrate ions mitigate Cl injury (Bar et al., 1997; Wiesman, 1995; and Britto et al., 2004). Fourthly, rootstocks that sequester Cl protect shoots from Cl damage, but if osmotic stress were the cause of damage, the damage would be hydraulically transmitted to the shoot (Bernstein et al., 2004). Fifthly, osmotic stress usually causes a greater reduction in shoot growth than root growth; however, Cl injury reduces root growth more than shoot growth (Bernstein et al., 2004).

3.2.3.3 The Effect of Salinity and the Sodium Ion on Chloride Response

Determining the relative importance of Cl ion-specific toxicity to osmotic stress is important in establishing how Cl affects avocados in the presence of salinity and ions associated with salinity. To determine if ion toxicity is the true and only cause of Cl injury, experimenters must be able to isolate the Cl ion – an impossible task because the Cl ion exists as part of a salt compound. However, it is possible to study responses to Cl salts that contain different cations, such as Na, Ca, and magnesium, to compare the effects that Cl might have in the


RDD\050590004 (CLR2820.DOC) 3-25

presence of different cations. It is also possible to create isosmotic solutions (those of equal osmotic potential) using ions other than Cl such as nitrate, because nitrate is a solute that changes the osmotic potential of a solution in the same way that Cl does. The following descriptions are all of experimental studies.

The first indication that ions such as Ca and Na had different effects on the severity of Cl injury was documented by Ayers (1950). In this experiment, the tip burn typical of Cl injury occurred more severely and sooner in NaCl treatments than in CaCl2 treatments. Haas and Brusca (1955) noted that tip burn was more severe when there is an inadequate supply of Ca and magnesium, and an excess of sulfate, Na, and other elements (not specified). Haas (1950a) also observed that excessive Na caused necrotic spotting in avocado leaves, but Ca helped to counteract that response. Plants that displayed Na injury also had damaged roots. Although plant growth, in general, was better when both Na and Ca were present, plant growth was best when Ca greatly exceeded Na in the solutions used to irrigate the avocado trees. Haas (1950b), as mentioned previously, found that tip burn typical of Cl injury occurred only when Cl concentration, applied as CaCl2, reached 442 mg/L in a series of treatments. This result is not consistent with the results obtained by those researchers who have tested Cl sensitivity in avocados using NaCl, nor is it consistent with the experience of local researchers and UCCE agents.

Mickelbart and Arpaia (2002) theorized that Na exacerbated the effects of Cl in their experiment on salinity tolerance in avocados. The leaf damage they observed was typical of Cl injury even though Na levels were very high in damaged leaves and were correlated with the degree of damage.

Serrano (2002) described one physiological relationship that might account for the link between Na- and Cl-specific ion toxicity. Cl transport into vacuoles (compartmentation) is an important function in salt-tolerant plants. A defect in the gene that encodes for this transport leads to sensitivity to toxic cations including Na. Another mechanism that might account for the connection between the toxic effects of Na and Cl was described by Spiegel et al. (1987). Na in large concentrations is known to displace Ca from the root-cell membranes, which causes leakage of potassium and other plant metabolites from the root. Therefore, maintenance of adequate potassium concentration is necessary for cellular function under saline conditions. Interestingly, Kadman and Ben-Ya’acov (1969) noticed that salt-sensitive avocado trees increased their uptake of potassium under saline conditions, and transported Cl to leaves in the form of potassium Cl. Salt-tolerant avocados accumulated and transported Cl in association with Ca.

These Na ion mechanisms could account for the association of salinity with intensification of Cl injury. Reinhold and Guy (2002) offer another reason why salinity might worsen the ion toxic effects of Cl. Cl uptake by plants is “uphill,” meaning plants must expend energy to take up Cl, which is required by plant cells in small amounts. However, there is some evidence that at very high salinities, this gradient might be reversed, allowing Cl to enter plant cells passively.

Bernstein et al. (2004) demonstrated that avocado root growth is more sensitive to salt stress than shoot growth, a unique trait among plants. They proposed the unique morphology of the avocado root, including few root hairs, low degree of root branching, and the tendency for the majority of the root mass to remain in the top 6 inches of soil, as a reason for its


3-26 RDD\050590004 (CLR2820.DOC)

extreme sensitivity to salinity. They further proposed that the reduction of developing root tissue mass under stress might also result in reduced transport of growth regulators from the root to the shoot, and might affect shoot growth and productivity. Thus, salt sensitivity of avocados might be related to physiological factors in addition to the osmotic stress that can reduce water uptake under highly saline conditions.

The results of these types of experiments indicate that the effect of Cl depends on the presence of ions that either exacerbate or lessen its toxicity. Na, for example, appears to have ion-specific osmotic and toxic effects of its own that might also augment the injury caused by Cl. On the other hand, cations other than Na found in Cl salts might decrease the toxic effects of Cl. A third interaction involves Cl ions and other ions that are electrochemically similar, such as nitrate and sulfate, which can substitute for Cl uptake.

3.2.3.4 Interactions with Other Negatively Charged Ions

Nitrate and sulfate compete with Cl ions in the soil solution because they have similar mobility properties to Cl. Because they are negatively charged, they move easily with water. For this reason, nitrate can decrease Cl accumulation in plants, when it is taken up from the soil solution in place of Cl.

Wiesman (1995) demonstrated that nitrate ion content was higher in the leaves of avocados with less Cl leaf injury than avocados on another rootstock that showed higher Cl injury.

Bar et al. (1997) found that adding nitrate to irrigation water laden with Cl reduced Cl accumulation in the plant and alleviated its adverse effects. They concluded that water containing high Cl levels might be used to irrigate avocados, provided that nitrate is supplied continuously at a molar concentration equivalent to half that of Cl. They further concluded that the reduction of plant Cl levels by nitrate involves inhibition of Cl uptake, because in all treatments nitrate uptake was preferential to Cl uptake. The physiological explanation is that nitrate is reduced (acquires a positive charge) after uptake, whereas Cl maintains its negative charge. For this reason, active uptake of Cl is diminished as the Cl gradient builds up during its accumulation, making it increasingly difficult for the plant to actively take up Cl. As a result, the Cl:nitrate ratio in the plant is always higher than that in the nutrient solution, and the plant preferentially takes up nitrate over Cl.

Montgomery Watson (1997), however, did not observe higher leaf nitrogen content in the irrigation water with higher Cl and higher nitrogen. The supply of nitrogen might not have been adequate in amount or consistency to achieve the effect that Bar et al. (1997) refers to. Shalhevet (1999) cautions against the practice of overapplying nitrogen to mitigate the effects of Cl, citing results from Steinhardt et al. (1995), who demonstrated that long-term overapplication of nitrogen eventually caused a decrease in avocado yield.

3.2.3.5 Significance of Chloride Injury Mechanisms to the Chloride Threshold Development

The findings presented above are summarized as follows:

Although Cl exclusion has been identified as a mechanism employed by salt-tolerant avocado varieties and not by salt-sensitive varieties, relatively little is known about the transport of the Cl ion and the targets of Cl ion toxicity in avocado trees.


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Evidence exists that Cl produces a specific-ion toxic effect in avocados, which likely occurs at a lower level of Cl and salinity than the osmotic effect that results from Cl salts.

Cl toxicity is affected by interactions with other ions that directly and indirectly impact the physiological functions of Cl in plants, and the overall health of the plant.

Salinity and the specific ion toxicity of Na are directly linked with the extent of Cl injury, and tend to exacerbate its effects.

Nitrate ions can substitute for Cl ions in plant uptake and can therefore help prevent accumulation of Cl in plant tissues. The practical implications and yield impacts of maintaining nitrogen levels in the soil solution to facilitate this practice are not well understood.

It is clear from these findings that the mechanisms of Cl injury in avocados are influenced by many factors, most of which are not well understood. Therefore, it would be erroneous to recommend a threshold without knowing the main salts that are present in the irrigation water. Although Ca, potassium, and magnesium salts likely decrease Cl injury, Na salts likely exacerbate Cl injury through Na ion-specific toxicities and the effects of salts by creating osmotic stress and hindering plant physiological functions.

Although the worst-case scenario could be assumed (the presence of the combination of salt ions that exacerbate the effect of Cl to the greatest degree), the development of a threshold based on that assumption would be uncertain because there is no quantitative relationship between Cl and other ions that results in particular effects. In other words, although Na is associated with an increase in Cl injury, the factor that correlates Na with Cl injury is not known.

3.2.4 Recommendations

The most reasonable type of threshold that can be determined from the literature presented above is a Cl hazard level, or concentration of Cl in irrigation water at which Cl injury in avocados could, but does not necessarily, occur. The following discussion relates to the Cl hazard level for Mexican-rootstock avocados.

No evidence suggests that the Cl hazard level is below 100 mg/L. No scientific studies or extension specialists with experience in the Upper SCR have suggested that Cl injury occurs below 100 mg/L. Therefore, the lower limit of the Cl hazard range is reasonably certain.

The upper range is less certain. Above this concentration, the Cl hazard level has been interpreted up to 178 mg/L. There is reason to believe this upper value (proposed by Bingham et al. [1968]) is too high for the following reasons:

No other studies, sources of data, or documentation of experiential knowledge corroborate this value. One study (or even two) is not enough evidence on which to base a Cl hazard level.

The study was performed on sand cultures in a controlled environment and does not represent commercial field conditions. Although it is valuable as a sand-culture study, field studies are necessary to substantiate its findings.


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The interpretation of the data by other researchers is different than that of the authors who conducted the study. Therefore, the conclusions from the study are not consistent with other findings.

The type of Cl salts used in the study were variables that were not addressed by the authors, but likely influenced the outcome of the study. The Ca and magnesium salts used in the study likely raised the Cl concentration at which Cl injury would have occurred if Na salts were used.

Reviewed sources that consider both local conditions (Grattan and Oster, 2002) and non-site-specific conditions (Maas, 1990 and Ayers and Westcot, 1985) recommend Cl hazard levels for Guatemalan and West Indian rootstocks that approximate or are below this value; however, these rootstocks are well known to be more salt tolerant than Mexican rootstocks.

Therefore, it is reasonable to propose that the upper limit of the Cl hazard range is lower than 178 mg/L. At Cl concentrations between 120 and 178 mg/L, Cl injury has been demonstrated to occur in several studies. For this reason, the recommendations for the Cl thresholds that are above 100 mg/L converge on 120 mg/L (approximately). The applicability of this value has some limitations, because it is derived from sources that are not site specific to the Upper SCR. However, no valuable evidence suggests another proposed Cl level anywhere between 120 and 178 mg/L.

Although there is clearly not enough evidence to propose an absolute threshold with the literature presently available, the best estimate of a Cl hazard concentration ranges from 100 to 120 mg/L. Below this range, no evidence shows that Cl injury occurs in avocados. Beyond this range, Cl injury has likely already begun to occur. This range is likely the result of uncertainty caused by natural variability in avocado populations, management practices, and interactions with other ions that either augment or diminish the toxic effects of the Cl ion. To reiterate, Cl injury in avocados of Mexican-race rootstock is possible in this range, depending on irrigation water quality, management practices, and site conditions.

The certainty of the lower limit of the range is enhanced by support from experience of local conditions in the Upper SCR and surrounding areas, documented by UCCE agents and agricultural consultants. The uncertainty of this lower limit arises from the lack of controlled and well-documented studies that explicitly confirm this value. The certainty of the upper limit of this range, on the other hand, is a result of recommendations from documented sources and studies; whereas, the uncertainty is a result of the lack of site specificity to the Upper SCR.

3.2.5 Works Cited

Amrhein, C. 1999. Review of the Report Titled, City of Escondido, Avocado Pilot Project Final Report, An Evaluation of Reclaimed Water for Use on Avocados, Five Year Study Report. Published February 1997.

Arpaia, M. L., G. W. Witney, G. S. Bender, D. S. Stottlemyer, and J. L. Meyer. 1995 and 1996. “Irrigation and Fertilization Management of Avocado.” California Avocado Research Symposium.


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Ayers, A. D. 1950. “Salt Tolerance of Avocado Trees Grown in Culture Solutions.” California Avocado Society 1950 Yearbook. 34:139-148.

Ayers, R. S. and D. W. Westcot. 1985. Water Quality for Agriculture. Food and Agricultural Organization of the United Nations (FAO). Irrigation and Drainage Paper 29, Rev. 1.

Bar, Y., A. Apelbaum, U. Kafkafi, and R. Goren. 1997. “Relationship between Cl and Nitrate and its Effect on Growth and Mineral Competition of Avocado and Citrus Plants.” Journal of Plant Nutrition. 20(6):715-731.

Ben-Ya’acov, E. Michelson, M. Zilberstaine, Z. Barkan, and I. Sela. 1992. “Selection of Clonal Avocado Rootstocks in Israel for High Productivity under Different Soil Conditions.” Proceedings of the Second World Avocado Congress. 1992:521-526.

Bergh, B. 1967. “Reasons for Low Yields of Avocados.” California Avocado Society 1967 Yearbook. 51:161-172.

Bernstein, L. 1965. “Salt Tolerance of Fruit Crops.” Agricultural Research Service, U.S. Department of Agriculture Bulletin.

Bernstein, N., A. Meiri, and M. Zilberstaine. 2004. “Root Growth of Avocado Is More Sensitive to Salinity than Shoot Growth.” Journal of the American Society for Horticultural Science. 129(2):188-192. March.

Bingham, F. T. and L. B. Fenn. 1966. “Chloride Injury to Hass Avocado Trees: A Sandculture Experiment.” California Avocado Society Yearbook. 50: 99-106.

Bingham, F. T., L. B. Fenn, and J. J. Oertli. 1968. “A Sandculture Study of Cl Toxicity to Mature Avocado Trees.” Soil Science Society of America Proceedings. Volume 32.

Bingham, F. and S. Richards. 1958. “Effects of Irrigation Treatments and Rates of Nitrogen Fertilization on Young Hass Avocado Trees. III. Changes in Soil Chemical Properties.” Proceedings of Journal of American Society for Horticultural Science. 71:304-309.

Branson, R. L. and C. D. Gustafson. 1972. “Irrigation Water - A Major Salt Contributor to Avocado Orchards.” California Avocado Society Yearbook.

Britto, D., T. Ruth, S. Lap, and H. Kronzucker. 2004. “Cellular and Whole-plant Cl Dynamics in Barley: Insights into Cl – Nitrogen Interactions and Salinity Responses. Planta. 218:615-622.

Chartzoulakis, K., A. Patakas, G. Kofidi, A. Bosabalidis, and A. Nastou. 2002. “Water Stress Affects Leaf Anatomy, Gas Exchange, Water Relations and Growth of Two Avocado Cultivars.” Scientia Horticulturae. 95:39-50.

Crowley, D. and M. L. Arpaia. 2000. “Rootstock Selections for Improved Salinity Tolerance of Avocado Continuing Project: Year 4 of 6.” Proceedings of California Avocado Research Symposium.

Crowley, D., W. Smith, and M. L. Arpaia. 2002. “Rootstock Selections for Improved Salinity Tolerance of Avocado Continuing Project: Year 5 of 6. Proceedings of California Avocado Research Symposium.


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Downton, W. 1978. “Growth and Flowering in Salt-stressed Avocado Trees.” Australian Journal of Agriculture Resources. 29:523-34.

Embleton, T., Mitsuo Matsumura, W. Storey, and M. Garber. 1962. “Chlorine and Other Elements in Avocado Leaves as Influenced by Rootstock.” Proceedings of the American Society for Horticultural Science, Volume 80. Includes: Embleton, T., Mitsuo Matsumura, W. Storey, and M. Garber. 1961. “Cl and Avocado Rootstocks.” California Avocado Society 1961 Yearbook. 45:110-115.

Faber, Ben/University of California Cooperative Extension. 2005. Telephone conversation with Stephanie Tillman/CH2M HILL. February 24.

Faber, B. 2004. Ed. C. Kallsen. “One, One Hundred, One Thousand.” Topics in Subtropics Newsletter Vol. 2, No. 2. April-June.

Faber, B., M. Arpaia, and M. Yates. 1995. “Irrigation Management of Avocado in a California Coastal Environment.” Proceedings of the World Avocado Congress III. 1995:189-195.

Gazit, S. and A. Kadman. 1976. “Growing Avocados in Areas of High Salinity.” Proceedings of the First International Tropical Fruit Short Course: The Avocado, p. 58-60.

Gonzales-Rosas, H., S. Salazar-Garcia, G. Ramirez-Reyes, J. Rodriguez-Ontiveros, and A. Ramos-Villasenor. 2003. “Preliminary Results on In Vitro Selection for Tolerance to Cl Excess in Avocado.” Revista Chapingo Serie Horticultura. 9(1):39-43.

Grattan, S. and J. Oster. 2002. Drought Tip 92-19 Water Quality Guidelines for Trees and Vines. Land, Air and Water Resources, University of California, Davis, California.

Greenway, H. and R. Munns. 1980. “Mechanisms of Salt Tolerance in Nonhalophytes.” Annual Reviews in Plant Physiology. 31:149-90.

Gustafson, C. 1976. “Avocado Water Relations.” California Avocado Society 1976 Yearbook. 60:57-72.

Gustafson, C., A. March, R. Branson, and S. Davis. 1972-73. “Drip Irrigation Experiments with Avocados in San Diego County.” California Avocado Society 1972-73 Yearbook. 56:109-112.

Gustafson, C. D. 1962. “The Salinity Problem in Growing Avocados.” California Avocado Society 1962 Yearbook. 46:100-105.

Haas, A. 1950a. “Calcium in Relation to the Effects of Sodium in Avocado Seedlings.” California Avocado Society 1950 Yearbook. 34:161-168.

Haas, A. 1950b. “Effect of Sodium Cl on Mexican, Guatemalan, and West Indian Avocado Seedlings.” California Avocado Society 1950 Yearbook. 34:153-160.

Haas, A. 1950c. “Rootstock Influence on the Composition of Scion Avocado Leaves.” California Avocado Society 1950 Yearbook. 34:149-152.

Haas, A. 1928. “Relation of Chlorine Content to Tip Burn of Avocado Leaves.” California Avocado Society 1928 Yearbook. 12:57.

Haas, A. and J. Brusca. 1955. “Cl Toxicity in Avocados.” California Agriculture. 9(2):11-12.


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Kadman, A. 1963. “The Uptake and Accumulation of Cl in Avocado Leaves and the Tolerance of Avocado Seedlings under Saline Conditions.” American Society for Horticultural Science. 83:280-286.

Kadman, A. and Ben-Ya’acov. 1969. “Selection of Rootstocks and Other Work Related to Salinity and Lime.” The Division of Subtropical Agriculture. The Volcani Institute of Agricultural Research 1960-1969, Section B, Avocado, p. 23-40.

Kurtz, C., I. Guil, and I. Klein. 1992. “Water Rate Effects on Three Avocado Cultivars.” Proceedings of Second World Avocado Congress. 1992:357-364.

Lahav, E. and A. Aycicegi-Lowengart. 2003. “Avocado Mineral Nutrition: The Water-Nutrients Relationship.” Proceedings of World Avocado Congress. 2003:349-357.

Lahav, E., R. Steinhardt, and D. Kalmar. 1992. “Water Requirements and the Effect of Salinity in an Avocado Orchard on Clay Soil.” Proceedings of Second World Avocado Congress. 1992:323-330.

Letey, J. and A. Dinar. 1986. “Simulated Crop-Water Production Functions for Several Crops When Irrigated with Saline Waters.” Hilgardia. Volume 54, No. 1.

Maas, E. V. 1990. “Crop Salt Tolerance.” In: “Agricultural Salinity Assessment and Management,” K.K. Tanji (Ed.). New York: American Society of Civil Engineers.

Maas, E. V. 1984. Ed. B. R. Christie. “Salt tolerance of plants.” The Handbook of Plant Science in Agriculture. Boca Raton, Florida: CRC Press.

Meiri, A., U. Yanai, N. Bernstien, R. Strul, and M. Zilberstaine. 1999. “Irrigation Frequency Affects Soil Salinity of Drip Irrigated Avocado.” Proceedings of Avocado Brainstorming. 1999:81-83.

Mickelbart, M. and M. Arpaia. 2002. “Rootstock Influences Changes in Ion Concentrations, Growth, and Photosynthesis of Hass Avocado Trees in Response to Salinity.” Journal of American Society of Horticultural Science. 127(4):649-655.

Montgomery Watson. 1997. City of Escondido Avocado Pilot Project: An Evaluation of Reclaimed Water for Use on Avocados, Five Year Final and Summary Report.

Oster, J. and M. Arpaia. 2002. “Setting TMDLs for Salinity and Cl Based on Their Effects on Avocado (Hass) Productivity.” In: J. C. McGahan (ed.). Proceedings. Helping Irrigated Agriculture Adjust to TMDLs. Sacramento, California, October 23-26. 2002:241-252. U.S. Committee on Irrigation and Drainage, Denver, CO.

Partida, G. J. 2002. Declaration of Dr. Gregory J. Partida Horticulture/Plant and Soil Science Department, California State Polytechnic University Pomona, California. County Sanitation Districts of Los Angeles County.

Reinhold, L. and M. Guy. 2002. Ed. A. Läuchli and U. Lüttge. “Function of Membrane Transport Systems under Salinity: Plasma Membrane.” Salinity: Environment-Plants-Molecules. Boston, MA: Kluwer Academic Publishers.


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Richards, Jim. 2005. Presentation made in Fillmore, California, to the Agricultural Technical Advisory Panel (AGTAP) for the Upper Santa Clara River TMDL Collaborative Process: Determination of the Protective Chloride Threshold for Salt-sensitive Agriculture in the Upper Santa Clara River Watershed. January 28.

Serrano, R. 2002. Ed. A. Läuchli and U. Lüttge. “Halotolerance Genes in Yeast.” Salinity: Environment-Plants-Molecules. Boston, MA: Kluwer Academic Publishers.

Shalhevet, J. 1999. “Salinity and Water Management in Avocado.” Proceedings of Avocado Brainstorming. 1999:84-91.

Spiegel, Y., D. Nezer. and U. Kafkafi. 1987. “The Role of Ca Nutrition on Fusarium-wilt Syndrome in Muskmelon.” Journal of Phytopathology. 118:200-226.

Steinhardt, R., D. Kalmar, A. Miari, and E. Lahav. 1995. “VC65 Rootstock Inducing Salinity-resistance and Productivity to Fuerte Avocado.” Alon Naotea. Volume 49, No. 10:460.

Thomas, E. 1932. “Effects of Chlorides in the Soil on Avocado Trees.” California Avocado Association 1932 Yearbook. 17:48-49.

Trask, E. 1960. “Some Factors Affecting the Accumulation of Chlorides in Avocado Soils.” California Avocado Society 1960 Yearbook. 44:38-39.

University of California Committee of Consultants. 1975. Water Quality for Agriculture.

Wiesman, Z. 1995. “Rootstock and Nitrate Involvement in Ettinger Avocado Response to Cl Stress.” Scientia Horticulturae. 62:33-43.

3.3 Evaluation of Strawberry Studies

This section discusses the evaluation of strawberry literature. This literature is grouped into the following two primary categories for discussion purposes:

1. Experimental Studies 2. Review Publications

Within each of these categories, articles could be categorized into those that included a focus on Cl impacts to strawberries and those that did not.

3.3.1 Experimental Studies

Study literature included articles that presented an experiment. Most of this literature presented studies about salinity effects on strawberries. Many of these studies addressed salinity only and did not distinguish Cl from other salts through either separate analyses or Cl and non-Cl treatments. However, three studies did address both salinity and Cl effects. These studies are discussed in more detail below.

All evaluated study articles are listed in Table 3-7 along with a brief statement describing whether they did or did not address Cl.

Three studies specifically examined Cl in some way, including Ehlig (1961), Ehlig and Bernstein (1958), and Lamberts et al. (1989). These were the only articles found in the literature that provided data aimed at differentiating Cl effects on strawberries from other


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salinity effects. However, each of these articles had limitations relative to the strength of their conclusions or their applicability to the Upper SCR.

TABLE 3-7

Study Literature and Whether It Differentiated between Chloride and Sodium through Separate Analysis or Treatments

Author Chloride Effects Differentiated from Salinity Effects?

Ehlig, 1961 Yes

Ehlig and Bernstein, 1958 Yes

Lamberts et al., 1989 Yes

Brown and Voth, 1955 No

Giuffrida, 2001 No

Hansen and Bendixen, 2004 No

Kepenek and Koyuncu, 2002 No

In Ehlig and Bernstein (1958), a stated objective was, “to study osmotic and specific ion effects on growth of strawberries in sand culture.” In this study, Lassen and Shasta varieties were grown in sand beds. Treatments of both Cl salts and non-Cl salts were applied to representative plots.

Results showed that plant injury was related to plant tissue Cl levels and occurred most severely on the two highest Cl treatments (1,237 and 1,431 mg/L Cl). However, results showed that visible plant injury was observed in all treatments on both varieties (including control) in hot weather, suggesting possible influences on injury outside of added treatments.

This article stated, “marginal burn was very slight or absent…when Cl contents did not exceed about 35 meq per 100 g dry weight.” It also stated that the osmotic pressure of the nutrient solution was the predominant factor in determining growth. This was based on the fact that “growth of Lassen was as poor on the Na2SO4 treatment in the absence of any signi-ficant marginal burn as on the Cl treatments” (Ehlig and Bernstein, 1958). This proves that the osmotic effect of non-Cl salinity treatments was as great as the Cl treatments with respect to growth. The question remains about whether growth impacts occur at lower Cl levels than visible impacts, and whether these impacts are translated into yield impacts. This part of the study did not examine yield or fruit quality, and intentionally removed flowers, focusing on impacts to vegetative growth. (A separate study described in this paper did examine yield impacts where electrical conductivity variation was generated by the ratio of NaCl to CaCl2).

Several factors in this study result in potentially limited applicability to the Upper SCR. Varieties grown, soil conditions, and climate factors are different than those in this area. Additionally, the irrigation method was not specified in this study, and irrigation-water Cl levels were varied from the planting date, providing an establishment period with lower salt concentrations prior to differential treatments. This practice is not representative of a field condition where water quality applied at planting would likely be similar to that applied throughout most of the season.


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In Ehlig (1961), Cl accumulation from salinized treatments was measured. This study measured Cl accumulation in plants grown in aquaculture that were given salinized irrigation treatments with specific concentrations of Na and/or Cl. The primary purpose was to compare Cl uptake from sprinkler versus root irrigation applications. Cl concen-trations were related to visible plant injury effects. Again, Cl concentrations in plant tissue were compared with qualitative assessments of plant injury in the form of leaf burn. Other potential affects, such as stunting or yield impact, were not evaluated. Therefore, the thresholds mentioned are limited because negative effects that could occur before leaf necrosis were not monitored. This study also has a limited applicability because it was conducted in an environment quite different from the Upper SCR with respect to irrigation management, climate, and soils.

In Lamberts et al. (1989), the effects of Cl:sulfate ratios in nutrient solutions on strawberry Cl uptake and growth were evaluated after cold conditioning.

The study noted a significant positive relationship between supplied Cl and Cl uptake, and showed no significant difference in plant growth or fruit production as a result of Cl. However, it cited high variability in plants, and many study implementation parameters were not provided. Irrigation management and methods were not provided in the literature. Additionally, this study was focused on examining management practices and varieties that are not applicable to the Upper SCR. Cold storage is not practiced in the Upper SCR. For these reasons, the applicability of the conclusions of this study in the Upper SCR is limited.

3.3.2 Review Publications

Review publications did not focus on presenting an experiment, but provided general background information on strawberry production, including irrigation techniques and management, fertilization, production schedules, and other cultural practices. Most of these articles were focused on salinity management and guidelines. This literature can further be grouped into articles that provided information about Cl impacts on strawberries and those that did not provide Cl-specific information.

3.3.2.1 Review Publications that Provided Chloride Information

In all cases, review publications that provided Cl guidelines did not cite sources or provide supporting discussion for the specific concentration recommended. For this reason, guide-lines provided in these articles left many unanswered questions about how they should be applied and whether they were applicable for the conditions and management practices in the Upper SCR. Common undefined factors about the applicability of these guidelines included irrigation method, irrigation management practices, and production schedule.

Table 3-8 provides a summary of the Cl guidelines that were obtained from review publications and a brief statement regarding what limitations to these guidelines were noted in literature evaluation.

Other resources that cited Cl recommendations for strawberries also fell into this category. Often it appeared that these were citing other literature reviewed in this evaluation or the source was not provided. Strand (1994) stated that if tissue levels of Cl are “above 0.5%, salt toxicity is indicated.” Maas (1987) stated that “furrow irrigation with water containing more than 100 mg/l of sodium or Cl could result in salt accumulation sufficient to produce


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measurable decreases in yields without causing visible plant symptoms.” This literature did not provide the source or supporting information for the guideline provided and cited other literature that is discussed elsewhere in this evaluation.

TABLE 3-8

Chloride Guidelines Obtained from Review Publications

Author Chloride Guideline Limitation/Conditions

Manitoba Agriculture, 2001

Water quality is satisfactory for strawberries if Cl is less than 3 meq/L.

No background data or source were provided. This guideline was intended for strawberry production in Manitoba, Canada, where strawberries are grown perennially and sprinkler irrigation is used.

Australian and New Zealand Environment and Conservation Council, 1992

Threshold for Cl irrigation water by root uptake is 110 to 180 mg/L.

The literature was a set of summary tables only, and no source information for the guidelines was provided.

Grattan, 1991 Cl in saturated soil extract should not exceed 175 to 260 mg/L.

No source or supporting information for this range was provided.

Schrader and Welch, 1990

Maximum Cl in soil solution is 5 to 7 meq/L and in irrigation water is 3 to 5 meq/L, in most cases. There are no restrictions on sprinkler irrigation water use if Cl concentration is less than 3 meq/L and on surface irrigation if less than 3 meq/L.

No sources or background data were provided for these guidelines. The applicable irrigation type was not specified for the two Cl ranges. For the other Cl guideline (<4 or <3 depending on irrigation type), the source was not provided, but matched data from a Food and Agricultural Organization of the United Nations water quality guidelines table. However, this was not stated.

Notes:

3 meq/L = 107 mg/L

5 meq/L = 178 mg/L

7 meq/L = 249 mg/L

3.3.2.2 Review Publications that Did Not Provide Chloride Information

The remaining review publications did not provide specific information relative to Cl impacts on strawberries. However, this literature did provide valuable background information. Table 3-9 provides a summary of these articles. Some important information from the articles that was valuable in establishing background information for the literature review is presented.

Applicability of this background information varied. Domato et al. (2000), Manitoba Agriculture (2001), and Wichmann (2004) provided some perspective from different strawberry growing regions and about different cultural practices, but yielded little background information that applied to California strawberry production.


The conclusions drawn in these articles pertain to specific strawberry varieties and study conditions. Because of changing production practices and study locations, these vary widely for the specific conditions in the Upper SCR. Although these studies provided valuable information about strawberry Cl uptake and did correlate increased uptake with increased leaf burn, they did not provide sufficient data to determine an appropriate Cl threshold for irrigation water.


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TABLE 3-9

Review Publications that Provided Background Information

Author Key Background Information

California Strawberry Commission, 2004 Acreage and growing districts in California

California production season (annual versus perennial)

Harvest method

Domato et al., 2000 Cultivar definitions (i.e., June bearing, everbearing, and day neutral)

Site selection guidelines (i.e., preference for light, soils, and good drainage)

Iowa cultural practices not specific to California (i.e., sprinkler irrigation, perennial production, matted row planting arrangement)

Summary of strawberry diseases

University of California Fruit and Nut Research and Information Center, 1999

California production statistics

Source of most nursery stock (California)

California growing and harvest seasons (annual)

Fumigation and other cultural practices

Approximation of varieties grown in various California regions

Summary of pests and diseases, and associated controls

Wichmann, 2004 Nutrient uptake

Preferred soil conditions

Welch and Beutel, 1987 California field preparation guidelines (i.e., soil grading, compost application, and preplant fertilization)

Voth and Bringhurst, 1967 Practices to help minimize soil salinity

The primary factors that lead to this conclusion are as follows:


The studies noted variability in plants or plant injury to control treatments, indicating potential outside factors in the results.

Study applicability to the Upper SCR was limited primarily with respect to the following factors:

Varieties grown Different or unknown irrigation methods Different or unknown irrigation management Different or unknown climate Different or unknown cultural practices

3.3.4 Works Cited

Australian and New Zealand Environment and Conservation Council. 1992. Australian Water Quality Guidelines for Fresh and Marine Waters.

Brown, J. G. and V. Voth. 1955. “Salt Damage to Strawberries.” California Agriculture. August. 1955:11-12.


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California Strawberry Commission. 2004. “Industry Backgrounder, California Strawberries at a Glance.” Available on Web page.

Domato, P., M. Gleason, and D. Lewis. 2000. “Production Guide for Commercial Strawberries.” Iowa State University Extension.

Ehlig, C. F. 1961.” Salt Tolerance of Strawberries under Sprinkler Irrigation.” Proceedings on Journal of American Society for Horticultural Science. 77:376-379.

Ehlig, C. F. and L. Bernstein. 1958. “Salt Tolerance of Strawberries.” Proceedings on Journal of American Society for Horticultural Science. 72:198-206.

Giuffrida, F., C. Leonardo, and G. Noto. 2001. “Response of Soilless Grown Strawberry to Different Salinity Levels in the Nutrient Solution.” Acta Horticulturae (International Society for Horticultural Science). 559:675-680.

Grattan, Stephen R. 1991. “Irrigation Management for Salinity Control in Strawberry Production.” Strawberry News Bulletin, California Strawberry Commission. April 10.

Hanson, Blaine and Warren Bendixen. 2004. “Drip Irrigation Evaluated in Santa Maria Valley Strawberries.” California Agriculture. 58(1):48-53.

Kepenek, K. and F. Koyuncu. “2002. Studies on the Salt Tolerance of Some Strawberry Cultivars under Glasshouse.” Acta Horticulturae (International Society for Horticultural Science). 573:297-304.

Lamberts, D. et al. 1989. “Cl Effects on Strawberry.” Acta Horticulturae. 265:285-290.

Manitoba Agriculture, Food and Rural Initiatives. 2001. “Strawberry Site Selection and Other Problems.” Available on Web page. Accessed: February 2004.

Maas, E. V. 1987. “Salt Tolerance of Plants.” Handbook of Plant Science in Agriculture. (ed.) B. R. Christie. CRC Press, Inc. Volume II:57-75.

Schrader, Wayne L. and Norman C. Welch. 1990. “Salinity Management in Strawberry Production.” Strawberry News Bulletin, California Strawberry Commission. December 10.

Strand, L. L. 1994. Integrated Pest Management of Strawberries. University of California Statewide Integrated Pest Management Project, Division of Agriculture and Natural Resources Publication #3351.

University of California Fruit and Nut Research and Information Center. 1999. “Crop Profile for Strawberries in California.” Available on Web page.

Voth, V. and R. S. Bringhurst. 1967. “The Affect of Cultural Practices on Salinity.” Strawberry News Bulletin, California Strawberry Commission. Vol. XIII, Bulletin No. 4.

Welch, Norm and Jim Beutel. 1987. “Summer Planting - Strawberries - Land Preparation - Soil Amendment - Preplant Fertilizer.” Strawberry News Bulletin, California Strawberry Commission. July 24.

Wichmann, W. Ed. 1996-2004. World Fertilizer Use Manual. International Fertilizer Industry Association. Available on Web site.


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3.4 Evaluation of Nursery Crop Studies

The information that was collected on Cl toxicity in nursery crops can be grouped into experimental studies and review publications. The information gathered from review publications can be further grouped into extension-type publications, literature reviews, and personal communications. Experimental efforts can be similarly organized into logical groups, including a series of experiments conducted at the University of California (UC) Davis, a series of experiments conducted at USSL, and other experiments. The following evaluation of nursery crop studies is organized on this basis.

3.4.1 Experimental Studies

The available experimental data on ornamental crops can be divided into three categories to facilitate discussion: a series of related sprinkler and drip irrigation experiments at UC Davis, experiments conducted at the USSL, and other studies.

3.4.1.1 UC Davis Experiments (Wu et al.)

The Department of Environmental Horticulture and Cooperative Extension at UC Davis conducted a series of studies on drip and sprinkler irrigation for a wide range of landscape plants (Wu et al., 2001a; 2001b; and 1999). The same group also conducted a closely related study with the City of San Jose, California (Wu et al., 2000). All of these were agency reports (Slosson Foundation), with the exception of Wu et al., 2001b, which was published in a major scientific journal. The main objective of these studies was to determine the salt tolerance of a wide range of landscape plants used in California.

A brief summary of these experiments follows. Field plots were randomly assigned to drip irrigation or sprinkler irrigation, and included both field-planted and container-grown plants. Three irrigation solutions were used, including potable water (40 mg/L Cl), 500 mg/L NaCl (300 mg/L Cl), and 1,500 mg/L NaCl (900 mg/L Cl). Plant species were selected according to their popularity in California gardens and landscapes, and with a goal of including plants representing a wide range of growth habits. A greenhouse experiment was also conducted on four plant species (two salt-sensitive and two salt-tolerant species, according to sprinkler irrigation results) to examine relationships between tolerance to sprinkler irrigation and drip irrigation. They also implemented a rapid screening procedure for salt tolerance, where plants in containers were placed outdoors and sprinkler irrigated with potable water, 500 mg/L NaCl, and 1,500 mg/L NaCl solutions (Wu et al., 1999). Demonstration plots established in San Jose included potable water and recycled water with an electrical conductivity of 1.3 dS/m and a Cl concentration of 160 mg/L (Wu et al., 2000).

Suggested thresholds from research papers are summarized in Appendix C, Table C-1, along with a summary of scores developed in the evaluation process.

Applicability. Field trials were conducted at UC Davis (Wu et al., 2001a; 2001b; and 1999) and at San Jose, California (Wu et al., 2000), and, therefore, have somewhat similar climate and growing conditions to the Upper SCR.

Both sprinkler and drip irrigation were used and compared in these studies (Wu et al., 2001b), similar to the Upper SCR. Irrigation frequency in the field studies was reasonably applicable to the Upper SCR, with irrigation every other day during the summer, and


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suspension of irrigation during wet winter weather (Wu et al., 2001a). Exposure was both through roots and leaves (Wu et al., 2001b) and, therefore, is applicable to Upper SCR nursery production. Similar to Upper SCR practice, saltwater solutions were not gradually increased or periodically applied (Wu et al., 1999 and 2000). Wu et al. (2000) provided no information on irrigation management.

Field studies included planting in a loam clay soil (Wu et al., 2001a and 2001b) and also included irrigation of container-grown plants (Wu et al., 2001a). Greenhouse studies were conducted using a mixture of sand, peat, and redwood sawdust (Wu et al., 2001b). Field-grown containers were also filled with the same mixture used in the greenhouse study (Wu et al., 2001a). Therefore, greenhouse studies and the portion of the field study that included container-grown plants are applicable to container culture in the Upper SCR. The portion of the field study that included planting in native soils is not representative of typical nursery practice, where plants are grown in containers.

No information on site soils was provided for the San Jose study (Wu et al., 2000).

Species selection was based on popularity in California gardens and landscaping (Wu et al., 2001b) and, therefore, is applicable to species that are or could be grown in the Upper SCR. The range of plants used in this series of studies included numerous a number of plants grown by Upper SCR nurseries, including oleander, liquidambar, and rose.

Specific Ion Toxicity. Separation of osmotic from specific ion effects was not within the scope of these studies, other than correlation of plant tissue Cl and Na concentrations with visible effects.

Mechanisms of Toxicity. No data were collected or explained in reference to mechanisms of toxicity.

Species Differences. There were significant differences among plants on Cl and Na uptake (Wu et al., 2000). Less salt-tolerant plants tended to accumulate greater concentrations of Na and Cl in the leaves (Wu et al., 2001b).

Quality Issues. Statistical analysis was used to determine if factors such as plant species and sprinkler as compared to drip irrigation were significant sources of variation for individual experiments (Wu et al., 2001b). The significance of treatment effects within individual plant species was not examined. Analysis of variance (ANOVA) was also used to determine if there were differences in plant growth among species for both soil- and container-grown plants at each salinity treatment (Wu et al., 2001a). No statistical comparisons were made of plant growth or visible effects within any plant species (Wu et al., 2001a). The lack of comparison was unusual, especially in light of their conclusion that salt tolerance to sprinkler irrigation was correlated with root-zone salt tolerance. The San Jose study (Wu et al., 2000) did not include an experimental design.

The following information regarding the implementation of these studies was not provided:

Little data were provided on the chemistry of the control solution (Wu et al., 2001a).

It is not clear from the text how the plants in the greenhouse study were irrigated (Wu et al., 2001b).


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Irrigation frequency was not given (Wu et al., 2000).

It is not clear when plants were established and how long treatments were applied (Wu et al., 2001a).

The method of irrigation used in the greenhouse study was not given, yet this study drove one of the major conclusions of the paper relating drip irrigation salt-tolerance data with sprinkler irrigation tolerance (Wu et al., 1999).

The duration of these experiments included 6 weeks for the rapid screening test (Wu et al., 1999), 16 weeks for the greenhouse experiment (Wu et al., 2000), and 45 weeks for the field study (Wu et al., 2001b). Therefore, the field study data can be considered the strongest and most relevant from these experiments, but still represents less than 1 year of data. Moreover, the ending results in Wu et al. (2001b) were for May, following a wet spring.

Conclusions. Drip irrigation resulted in less salt stress than sprinkler irrigation. Although there was evidence of leaf chlorosis in sensitive species after 6 weeks with a 500-mg/L NaCl solution (300-mg/L Cl), after 46 weeks, no chlorosis or reduction in plant growth were among even the most sensitive species tested (Wu et al., 2001b). In contrast, with sprinkler irrigation at the same salinity level after 46 weeks, some chlorosis was evident on the most sensitive species (Wu et al., 2001b). Thus, the results suggested an irrigation threshold of more than 300 mg/L Cl for drip, and less than 300 mg/L for sprinkler irrigation. Although data on leaf tissue Cl and Na were collected, the papers did not address separating Cl from Na toxicity effects.

In the San Jose study, using water with 160 mg/L Cl and sprinkler irrigation, no salt stress symptoms were observed for the 24 plant species used, even though plant tissue Na and Cl levels were significantly higher (P<0.001) than plants irrigated with the low-salinity control water (Wu et al., 2000). The authors did acknowledge the limitations of a 1-year study and that longer term impacts could emerge.

Wu et al. (2001a and 2001b) concluded that plant salt tolerance with sprinkler irrigation was positively related to salt tolerance with drip irrigation, and, therefore, sprinkler irrigation could serve as a rapid screening tool for landscape species. The utility of sprinkler irrigation as a predictive tool to assess plant tolerance is questionable. Wu et al., did not reference any supporting literature, and Maas (1990) clearly explained the reasons why tolerance to root-zone salinity might not be very well correlated with tolerance to sprinkler irrigation using water with elevated salts. Moreover, Wu et al., largely based this conclusion on a small greenhouse study including only four landscape species, the methods and results of which were not well explained.

Implications for Chloride Threshold. This series of papers had some of the most applicable information available for the determination of the Cl threshold for the nursery crop industry in the Upper SCR. They included drip and sprinkler irrigation, container-grown plants, and were conducted in a somewhat similar climate. Several of these papers were agency reports (Wu et al., 2001a; 2000; and 1999); the level of peer review is uncertain; and they were largely redundant, reporting results from the same experiments. Moreover, Wu et al. (2000) reported the results of a demonstration study, falling short of the standards of a research study. The container-grown plants study, highly relevant to the Upper SCR, which was included in Wu et al. (2001a), was not described in the peer-reviewed paper (Wu et al.,


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2001b). The salt treatments were applied as NaCl, without any Ca salts (Wu et al., 2001b), and Na effects were confounded with Cl effects. Most salt-tolerance tests were conducted with Na and Ca salts (Bernstein et al., 1972; Monk and Peterson, 1962; and Lunt et al., 1957). Unanswered questions regarding the implementation of these studies are numerous.

Sprinkler irrigation is important for nursery crop production in the Upper SCR. The strongest results from these studies suggest that the appropriate standard is probably less than 300 mg/L.

3.4.1.2 United States Salinity Laboratory Experiments

A series of three papers was published based on the results of experiments conducted at USSL (Bernstein et al., 1972; Francois and Clark, 1978; and Francois, 1982). The experimental methods, discussion, presentation of results, interpretations, and conclusions were similar for this series of papers. Each subsequent paper added additional plants to the database, with little variation in experimental methods. Widely referenced reviews on salt tolerance by Maas (1986 and 1990) included a summary of the data collected in this series of papers.

A summary of the experimental method for this series of papers follows. Ornamental shrub, groundcover, and tree species were established in field plots, and were flood irrigated with one of three solutions (control, 2,000 mg/L NaCl+CaCl2, and 4,000 mg/L NaCl+CaCl2). The associated Cl concentrations in the salt solutions were approximately 1,250 and 2,500 mg/L.

Applicability. All of these experiments were conducted at USSL in Riverside, California, and, therefore, are somewhat relevant to Southern California. However, the location and climate at Riverside were not explicitly tied to their conclusions on salt tolerance. Weather conditions at Riverside are more severe than in the SCR Valley, with a greater incidence of hot, dry weather likely to exacerbate salinity issues (Maas, 1990).

The range of plants used in this series of studies included numerous plants grown by Upper SCR nurseries, including bougainvillea, oleander, hibiscus, pittosporum, rose, star jasmine, viburnum, iceplant, palm, juniper, liquidambar, magnolia, and crape myrtle.

The flood irrigation of native soils used in these studies is considerably different from the drip or sprinkler irrigation methods used by container nurseries in the Upper SCR. Bernstein et al. (1972) included a subexperiment where plants were grown in sand tanks, also not representative of Upper SCR nursery production. Irrigation was applied weekly to the field plots during the summer in these studies; however, Upper SCR nurseries typically irrigate container materials every day to every other day in the summer. All uptake of irrigation water and soluble salts was through root uptake; therefore, results are at least partially relevant to container production, but no information on foliar uptake was provided.

In general, plants can tolerate higher levels of salinity if they have time to make internal adjustments (Banuelos, 2004, pers. comm.). Possible plant adjustments to salinity include compartmentalizing salts in vacuoles, control of uptake, and synthesis of organic solutes (Greenway and Munns, 1980). The field experiments in all three papers were initiated through a gradual application of increasing levels of salinity until the design treatments were fully applied. Growers in the Upper SCR will likely apply whatever water they have available, and will not be in a position to blend water supplies to gradually increase salinity.


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Specific Ion Toxicity. Only Bernstein et al. (1972) examined specific ion toxicity with irrigation solutions designed to be isosmotic. They conducted isosmotic tests using solutions prepared from NaCl, CaCl2+NaCl, CaCl2, and Na2SO4, each at a concentration designed to decrease water potential by 2.2 bar. It is difficult to confirm or disprove Bernstein et al.’s conclusions relative to Cl and osmotic effects because of the way they present the data. Growth data were not presented for isosmotic treatments, and visible evidence of toxic effects was not presented quantitatively. The data in Bernstein et al. (1972) suggested that plant responses vary widely, and that there might not be a consistent correlation of Na and Cl uptake data with overall salt tolerance. Bernstein et al. (1972) concluded that Cl tended to add leaf damage or early leaf drop to plants already stunted by osmotic effects of high salt.

In general, less-tolerant species accumulate higher levels of Cl in the leaves (Francois, 1982). Francois (1982) and Francois and Clark (1978) both conducted tissue testing of Cl and Na, but made no other exploration of the osmotic versus ion toxicity issue other than relative differences in plant uptake among plant species and comparisons of burned-leaf tissue concentrations with general literature values for Cl and Na injury. Francois and Clark (1978) and Francois (1982) found that Cl accumulation was greater than Na accumulation. In woody plants, marginal and tip leaf burning is typically found when leaf Cl concentrations are 1 percent (28 milliequivalents per 100 grams) (Bernstein and Hayward, 1958, as cited in Francois and Clark, 1978).

Mechanisms of Toxicity. This series of experiments did not explore mechanisms of toxicity, although Bernstein et al. (1972) discussed a hypothesis that excessive levels of Na and Cl impede stomatal closure. This was based on anecdotal evidence from observations of burned leaves of water-stressed landscape plantings near the study area with low Na and Cl in plant leaves.

Species Differences. A wide range of response to Cl is among the ornamental plants, includ-ing variability of the relationships between salt tolerance and Cl uptake, between Cl uptake and leaf effects, and the extent of visible leaf damage before leaf abscission (Bernstein et al., 1972). Leaf injury and high Cl accumulation in leaves were strongly associated for guava, rose, holly, ivy, hibiscus, and viburnum, species with poor to very poor overall salt tolerance (Bernstein et al., 1972). However, bottlebrush had good salt tolerance in terms of growth, but still showed leaf tip burn. This observation supports the theory that Cl effects might impact plants well before the influence of decreasing osmotic potential.

In terms of tolerance to soil salinity, tolerant species were minimally affected, if at all, by a 7-dS/m soil ECe; whereas sensitive species were severely damaged or killed by a soil ECe of 4 dS/m (Francois and Clark, 1978).

Quality Issues. All of these studies included a control and replication, but experimental design and randomization were not explained, and only summary data were provided. No statistical analysis of the data was done. All of the studies provided information on soil salinity thresholds for adverse effects that imply a greater degree of resolution than would seem possible from the three levels of salinity used. It is unclear how the summary figure used in all three papers, which presents soil salinity-related growth reduction thresholds and LD50 (the level of salinity resulting in the death of 50 percent of the plants [lethal dose]) values by species, was constructed from the data. The papers are unclear about whether there could have been sufficient variation in the level of soil salinity among the field plots to


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allow determination of the salt tolerance of a given species at an intermediate soil salinity value. For example, the orchid tree was assigned a maximum root-zone salinity of 4 to 5 dS/m, although average soil salinity levels were 1.5, 6.0, and 9.8 dS/m for the three levels of salinity applied (Francois, 1982). The uncertainty associated with the values presented is unknown.

In general, the level of documentation on how the studies were implemented is reasonable, although some questions remain such as the frequency of watering, soil moisture content, soil fertility, variability of soil salinity within plots receiving the same treatment, and the variability of plant growth and visible effects. Each of these experiments was 2 years or longer, providing reasonably representative data.

Conclusions. The conclusions were mainly limited to the relative tolerance of the species examined in terms of soil ECe thresholds, and these conclusions were supported by experimental results. The most salt-sensitive plants were able to tolerate a soil ECe of approximately 2.5 dS/m, with a growth reduction of less than 50 percent (Francois and Clark, 1978; Francois, 1982; and Bernstein et al., 1972). Maas (1990), summarizing the data from these papers, provided more conservative soil ECe values, with a maximum permissible soil ECe for most sensitive ornamental crop species of 1 to 2 dS/m. Bernstein et al. (1972) concluded that the relative ratings of salt tolerance among species were indicative of general salt tolerance, rather than Cl tolerance, even though Cl was by far the dominant anion contributing to soil salinity. This is contrary to the interpretation suggested by Maas (1990), who suggested that root-zone Cl tolerance could be derived from salt-tolerance tests conducted using primarily Cl salts.

An important consideration for nursery crops that differs from most agricultural crops is that the appearance of the plant is much more important than yield or growth (Townsend, 1980; Bernstein et al., 1972; Francois and Clark, 1978; and Francois, 1982). Evidence of foliar damage or loss of leaves can make the plants commercially unacceptable, even if effects on growth or survival are not significant (Maas, 1990). Bernstein et al. (1972) and Francois and Clark (1978), each working with a different set of ornamental plant species, showed that if growth reduction from excess salinity is less than 50 percent, then there is no observable leaf injury and there is no adverse effect on plant appearance. The findings of Francois (1982), working with another group of plants, suggested a slightly lower acceptable threshold for growth reduction of 40 to 50 percent.

Implications for Establishment of a Chloride Threshold. Several factors suggest that this series of papers is of only limited value for determining an irrigation water Cl threshold for ornamental plants. The major purpose and value of these papers is to provide the relative tolerance to soil ECe of a wide range of ornamental plant species. First, the leap must be made from soil ECe values to irrigation water Cl values. Secondly, the low-salinity treatment used in all of these studies contained 1,250 mg/L Cl, considerably higher than any threshold being contemplated for other sensitive crops. Thirdly, sprinkler irrigation is important to ornamental crop production in the Upper SCR, and these studies provided no information on sprinkler irrigation effects. Maas (1990) noted that sprinkler irrigation is very different from surface irrigation or root uptake. Leaf characteristics and the rate of absorption more strongly affect tolerance to sprinkler irrigation of saline water than


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tolerance to soil salinity, and tolerance to high root-zone salinity is not necessarily correlated with tolerance to sprinkler irrigation (Maas, 1990).

3.4.1.3 Other Studies

Research studies other than the set of closely related studies by Wu et al., and the USSL studies are evaluated in this section. These studies include those from a range of locations, including California, Virginia, Ohio, and Utah. A paper by Wu et al., which is not closely related to their other studies discussed previously, is also included in this section.

Applicability. The other studies reviewed have limited applicability. Studies that included hydroponic culture (Monk and Weibe, 1961 and Townsend, 1980) or excised plant tissue (Monk and Weibe, 1961) have limited applicability to containerized nursery crops in the Upper SCR. Flood irrigation of field-planted materials (Monk and Weibe, 1961) is also not directly relevant to Upper SCR nursery crop production, although results are probably somewhat correlated with drip irrigation. However, Wu et al. (1995) used sprinkler irrigation of containers, and is therefore relevant to Upper SCR practices. Information on irrigation management in some studies was so scant that it is not possible to determine the applicability of the study (Lunt et al., 1956). Irrigation as infrequently as once per week during the growing season (Monk and Peterson, 1962) does not represent nursery practice in the Upper SCR.

The dosing of saline irrigation water was highly variable in these studies and often in an approach far removed from Upper SCR nursery practice. Lunin and Stewart (1961) applied salt solutions in four applications separate from normal, nonsaline irrigation over the 4-month monitoring period. Monk and Weibe (1961) and Monk and Peterson (1962) increased the salt concentrations gradually in the field study. Wu et al. (1995) applied saline wastewater and interspersed freshwater irrigation with saline irrigation each week, an approach not feasible for Upper SCR growers. Two studies interspersed saline irrigations with freshwater irrigations each week (Wu et al., 1995 and Wu et al., 1998), an approach not generally possible for Upper SCR nurseries.

Experimental data on azaleas and camellias (Lunin and Stewart, 1961), and azaleas and gardenias (Lunt et al., 1957) are applicable to the Upper SCR. Wu et al. (1998) focused on species “commonly grown in California gardens and landscapes,” although it is not known if these are grown by any Upper SCR nurseries. Wu et al. (1995) did include some species relevant to Upper SCR nursery production, including pittosporum and azaleas. Townsend (1980) focused on species more common to the Midwest and northeast (white pine, pin oak, and honey locust), than to nursery crop production in the Upper SCR. Similarly, Monk and Weibe (1961) and Monk and Peterson (1962) examined salt tolerance among predominantly northern-latitude or higher elevation species.

Studies conducted outside of California, in dissimilar climates, are of limited applicability. These studies included Virginia (Lunin and Stewart, 1961), Utah (Monk and Weibe, 1961 and Monk and Peterson, 1962), and Ohio (Townsend, 1980). In contrast, studies at UC Los Angeles (Lunt et al., 1956 and 1957) can be considered more geographically and climatically relevant. Studies conducted at locations relatively near the coast of California (Wu et al., 1995 and 1998) have geographic and climatic relevance, although for greenhouse studies (Wu et al., 1995), this issue is less important.


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Specific Ion Toxicity and Osmotic Effect. Some studies (Townsend, 1980) appeared to assume that specific ion effects are the causal mechanism, but osmotic as opposed to specific ion effects are not specifically discussed. Lunin and Stewart (1961) included specific ion effects in their interpretations of the data, but this was not specifically part of their objectives or experimental design. Lunin and Stewart (1961) measured and correlated electrical conductivity of solutions and evapotranspiration, discussed this data collection in terms of osmotic effects, but made no measurements of relative irrigation water potential and plant tissue water potential. They collected no data on plant tissue concentrations, but suggested that limitations on water uptake were the major impact of increased salinity and that specific ion toxicity was at most a contributing factor. They base this on the results of Lunt et al. (1957), who found azaleas not especially sensitive to Cl. One study (Lunt et al., 1956) included treatments with a uniform concentration on a milliequivalent basis (e.g., base nutrient solution + 25 meq/L CaCl2 and base nutrient solution + 25 meq/L Na2SO4), and found no evidence that 25 meq/L Cl (888 mg/L) was “especially harmful” to azaleas, although there was some evidence of leaf drop and leaf tip burn. Simply measuring plant tissue Cl for various treatments (Wu et al., 1998) provides no conclusive evidence that the source of Cl injury is either osmotic or specific ion effect. In one case, no Na salts were included in the treatments, to allow simulation of a potassium Cl-based water softener regenerant wastewater (Wu et al., 1995).

Mechanisms of Toxicity. None of these experiments provided any information on mechanisms of Cl toxicity.

Species Differences. These studies found a wide range of response to salinity among ornamental species. Euonymous did not survive 4,000 mg/L NaCl+CaCl2, yet growth increased for green ash and honey locust (Monk and Peterson, 1962). Plant dry weight was significantly reduced for sycamore at 4,500 mg/L NaCl, whereas Japanese pagoda tree was not affected (Townsend, 1980).

The most sensitive species also had the highest levels of plant tissue Cl (Wu et al., 1995). However, species that had greater Cl concentrations in the leaves had the greatest relative growth based on dry-weight production (Wu et al., 1998).

Quality Issues. Townsend (1980) is rare among these papers in that it included a thorough statistical analysis. The study appeared to have a complete data set, it exhaustively explored the data, and the statistical analysis seems to be appropriate for the experimental design. Wu et al. (1995) conducted an ANOVA and means comparisons, but some of the interpretations are questionable, including weak correlations among plant tolerance and plant tissue Cl and Ca. Wu et al. (1998) presented results of an ANOVA, but no experi-mental design, randomization, or replication was described, and it lacked complete exploration of the data. The remaining sources (Lunin and Stewart, 1961; Lunt et al., 1956; Lunt et al., 1957; Monk and Weibe, 1961; and Monk and Peterson, 1962) conducted no statistical analysis at all.

Studies as short as 5 weeks (Townsend, 1980) exposure might provide some initial screening level data, but are probably not sufficient to determine definitive differences in salt toler-ance, especially for longer lived, woody species commonly grown by Upper SCR nurseries. Several other studies extended for less than 1 year (Lunin and Stewart, 1961; Lunt et al., 1957; Lunt et al., 1956; Wu et al., 1995; and Wu et al., 1998). Portions of some studies


3-46 RDD\050590004 (CLR2820.DOC)

extended for longer than 1 year (Monk and Weibe, 1961 and Monk and Peterson, 1962), although Monk and Peterson (1962) acknowledged that a 1.5-year study is not definitive for long-lived species, where cumulative effects could become important.

The older studies (Lunin and Stewart, 1961 and Lunt et al., 1956 and 1957) provided only modest levels of information on study implementation. The irrigation method used was not explicitly given (Lunt et al., 1956; Monk and Weibe, 1961; and Monk and Peterson, 1962). The frequency and volume of irrigation was not given, and the salinity of the irrigation water was not measured (Lunt et al., 1956). The duration of salinity treatments is not clear, and no information on soils was given (Monk and Weibe, 1961). The Cl concentrations in the irrigation solutions were not measured directly (Lunin and Stewart, 1961). In another case, no data were collected on Cl levels in plant tissue, no soils data were collected, and no clear explanation was provided describing the irrigation rate (Monk and Peterson, 1962). In yet another case, the Cl concentration of the irrigation water is not clear, greenhouse conditions were not described, the type of irrigation was not described, and the duration of the salt treatments was not clear (Wu et al., 1998).

Conclusions. A Cl level of 25 meq/L (886 mg/L) resulted in only slight leaf drop and tip burn, no chlorosis, and average growth of azaleas (Lunt et al., 1956). The growth of azaleas and gardenias was reduced by 50 percent or more with 51 meq/L total salts (approximately 1,400 mg/L Cl) (Lunt et al., 1957). In terms of soil salinity, 3 millimho per centimeter is the permissible limit for azaleas and camellias, even though some evidence of damage was seen at 2 millimho per centimeter (Lunin and Stewart, 1961).

Townsend (1980) found no adverse effects on tree height at approximately 1,200 mg/L Cl, but there were significant reductions in stem, root, and leaf biomass compared to the control in some species at the same level. The most salt-sensitive trees and shrubs did not survive irrigation using a 2,550-mg/L Cl solution in a field study, and results were similar for 2,230 mg/L Cl in solution culture (Monk and Weibe, 1961 and Monk and Peterson, 1962). An irrigation solution containing 1,484 mg/L Cl resulted in severe effects on the most sensitive species (Wu et al., 1995). Differences in Cl uptake led to differences in plant growth (Wu et al., 1995).

Implications for Chloride Threshold. There are significant limitations on the use of these studies for the establishment of a Cl threshold for nursery crops in the Upper SCR. These limitations include the applicability of the climate, soil conditions, irrigation management, irrigation methods, and plant species used. Other limitations include relatively short duration, little or no statistical analysis, and a low-salinity treatment that is relatively high in Cl. In most cases, Cl effects are also confounded with Na effects.

Therefore, the results of the studies reviewed in this section should not significantly influence the establishment of a Cl threshold for nursery crops in the Upper SCR.

3.4.2 Review Publications

3.4.2.1 Extension-type Publications

Extension service guidance on irrigation water quality for nursery crop production were reviewed from California (Farnham et al., 1985), North Carolina (Bailey et al., 1999),


RDD\050590004 (CLR2820.DOC) 3-47

Arkansas (Robbins and Klingaman, 2000), Australia (Stephens, 2002), New Jersey (Cabrera, 1998), and from a general document for the western United States (Bernstein, 1964).

These documents typically provided a discussion explaining that Cl can result in toxicity to sensitive species, and that Cl is also an important contributor to the overall osmotic effect of excess solutes (Bailey et al., 1999; Cabrera, 1998; Robbins and Klingaman, 2000; and Farnham et al., 1993).

Of the publications in this category, only Farnham et al. (1985) provided any specific links to research data. However, the research data provided in Farnham et al. (1985) were based on relative plant tolerance to irrigation water electrical conductivity, rather than irrigation water Cl. The general irrigation water quality thresholds for Cl in Farnham et al. (1985) were not directly linked to any specific research results. Bernstein (1964) provided a vague reference to USSL data when listing relative plant tolerance to soil ECe, without a specific citation.

These publications are often vague as to the applicability of the thresholds provided in terms of irrigation method, irrigation management, and plant species. For example, Bailey et al. (1999) stated that sprinkler irrigation of container stock is the only practical method, which is consistent with Upper SCR practice for most smaller container material. This statement implies that the Cl threshold given in Bailey et al. (1999) is based on sprinkler irrigation, but this cannot be conclusively determined from the text. Similarly, in Cabrera (1998) and Stephens (2002), the application method was not specifically tied to the suggested irrigation water Cl threshold. Farnham et al. (1985) did provide specific thresholds for root absorption (surface irrigation) and sprinkler irrigation. Suggested thresholds from extension-type sources are summarized in Appendix C, Table C-2, along with a summary of scores developed in the evaluation process.

The data in the table show that a range of values is suggested for irrigation water Cl. The highest scoring paper in this category was Farnham et al. (1985), primarily as a result of its high level of applicability to the Upper SCR. It was written for California, and provides specific recommendations for sprinkler and surface irrigation.

3.4.2.2 Personal Communications

Two private-sector nursery crop production experts (Bill Darlington/Soil and Plant Laboratory and George Gutman/Bordiers Nursery) who work in the Upper SCR were identified early in the process of developing the literature review. They both suggested that sprinkler irrigation and drip irrigation are important to nursery operations in the Upper SCR, that there is a wide range of plant tolerance, and that damage might occur with Cl concentrations greater than 3 meq/L (107 mg/L) and sprinkler irrigation with sensitive species (2004, pers. comm.). Their experience suggested that even without supporting controlled experiments, their opinion regarding the appropriate threshold for the nursery industry should receive considerable weight in the evaluation.

3.4.2.3 Literature Reviews

Maas (1987) provided a succinct review of the general processes associated with Cl-specific ion toxicity and Cl as an important contributor to an overall osmotic effect, but provided no specific Cl thresholds for any crops. No supporting references were provided. Carpenter


3-48 RDD\050590004 (CLR2820.DOC)

(1970) provided a list of the relative salt tolerance of ornamental plants to total salt, with an emphasis on plants adapted to the north-central and northeastern United States, along with an emphasis on the impacts of salt applications to roadways and impacts on adjacent ornamental plants. Neither review provided any specific information that can support the establishment of an irrigation water threshold for Cl.

Information on ornamental crops reviewed by Maas (1986 and 1990) only included salt-tolerance threshold data collected in experiments at USSL in Riverside, California, and is included along with specific discussions of those experiments in the following section.


It is reasonable to conclude from this review of the available information that there is a lack of sufficient evidence upon which to base a recommendation for a Cl threshold. The primary factors that lead to this conclusion are as follows:

Studies by Wu et al., came the closest to providing the needed information, but they showed evidence of adverse effects with sprinkler irrigation at 300 mg/L Cl, suggesting that the threshold value is lower than 300 mg/L. However, data were not sufficient to determine how much lower the standard should be. If all drip irrigation were used for all nursery crop production, it appears that a higher threshold might be justified according to these studies. It is also difficult to justify establishing a standard based on the results of only a few experiments by one research group.

The USSL studies provided a wealth of information on the relative salt tolerance for soil-planted and surface-irrigated plants, but included no information on sprinkler irrigation effects. Given the importance of sprinkler irrigation to Upper SCR nursery crop production, and the differential effects of root zone as compared to foliar exposure, the value of these studies in setting an irrigation water standard is quite limited.

Thresholds suggested by extension pamphlets and local experts are not clearly tied to experimental data, making it difficult to justify expenditures of substantial funds to meet the low values suggested.

Production of nursery crops in large containers (specimen trees) is a large component of the industry, and no data are available on Cl standards for the production of these crops. In addition, a huge array of plants is potentially important to the industry, and data were only available on a limited number of species.

3.4.4 Works Cited

Bailey, D., T. Bilderback, and D. Bir. 1999. Water Considerations for Container Production of Plants. North Carolina State University, Horticulture Information Leaflet #557.

Banuelos, Gary/U.S. Department of Agriculture/Agricultural Research Service/Water Management Research Lab. 2004. Personal communication with CH2M HILL. December.

Bernstein, L. 1964. “Reducing Salt Injury to Ornamental Shrubs in the West.” U.S. Department of Agriculture Home and Garden Bulletin. 95:6.


RDD\050590004 (CLR2820.DOC) 3-49

Bernstein, L., L. E. Francois, and R. A. Clark. 1972. “Salt Tolerance of Ornamental Shrubs and Ground Covers.” Journal of American Society for Horticultural Science. 97:550-566.

Cabrera, I. 1998. Evaluating Water Quality for Ornamental Plant Production. Rutgers Cooperative Extension Fact Sheet FS893.

Carpenter, E. D. 1970. “Salt Tolerance of Ornamental Plants.” American Nurseryman. 131:12-71.

Darlington, Bill/Soil and Plant Laboratory, Inc., Orange, California. 2004. Personal communication with CH2M HILL.

Farnham, D. S., R. F. Hasek, J. L. Paul. 1993. “Water Quality and Its Effects on Ornamental Plants.” Cooperative Extension University of California Division of Agriculture and Natural Resources Leaflet #2995.

Farnham, D. S., R. F. Hasek, and J. L. Paul. 1985. Water Quality: Its Effects on Ornamental Plants. University of California Cooperative Extension Leaflet #2995.

Francois, L. E. 1982. “Salt Tolerance of Eight Ornamental Tree Species.” Journal of American Society for Horticultural Science. 107:66-68.

Francois, L. E. and R. A. Clark. 1978. “Salt Tolerance of Ornamental Shrubs, Trees, and Iceplant.” Journal of American Society for Horticultural Science. 103:280-283.

Greenway, H. and R. Munns. 1980. “Mechanisms of Salt Tolerance in Nonhalophytes.” Annual Review Plant Physiology. 31-149-190.

Gutman, George/Bordier’s Nursery, Irvine, California. 2004. Personal communication with CH2M HILL.

Lunin, J. and F. B. Stewart. 1961. “The Effect of Soil Salinity on Azaleas and Camellias.” Proceedings on Journal of American Society for Horticultural Science. 77:528-532.

Lunt, O. R., H. C. Kohl, Jr., and A. M. Kofranek. 1957. “Tolerance of Azaleas and Gardenias to Salinity Condition and Boron.” Proceedings on Journal of American Society for Horticultural Science. 69:543-548.

Lunt, O. R., H. C. Kohl, and A. M. Kofranek. 1956. “The Effect of Bicarbonate and Other Constituents of Irrigation Water on the Growth of Azaleas.” Proceedings on Journal of American Society for Horticultural Science. 68:537-544.

Maas, E. V. 1990. “Crop Salt Tolerance.” In: “Agricultural Salinity Assessment and Management,” K. K. Tanji (Ed.). New York: American Society of Civil Engineers.

Maas, E. V. 1987. “Chloride.” In: McGraw-Hill Yearbook of Science and Technology.

Maas, E. V. 1986. “Salt Tolerance of Plants.” Applied Agricultural Research. 1(1):12-26.

Monk, R. and H. B. Peterson. 1962. “Tolerance of Some Trees and Shrubs to Saline Conditions.” Proceedings on Journal of American Society on Horticultural Science. 81:556-561.

Monk, R. and H. H. Weibe. 1961. “Salt Tolerance and Protoplasmic Salt Hardiness of Various Woody and Herbaceous Ornamental Plants.” Plant Physiology. 36:478-482.


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Robbins, J. and G. Klingaman. 2000. “Irrigation Water for Greenhouses and Nurseries.” University of Arkansas, Division of Agriculture, Cooperative Extension Service.

Stephens, R. 2002. Water Quality and Nursery Crop Nutrition. The Nursery Papers Issue No. 2002/11, Nursery & Garden Industry Australia and Horticulture Australia.

Townsend, A. M. 1980. “Response of Selected Tree Species to Sodium Chloride.” Journal of American Society on Horticultural Science. 105:878-883.

Wu, L. X. Guo, K. Hunter, E. Zagory, R. Waters, and J. Brown. 2001a. “Studies of Salt Tolerance of Landscape Plant Species and California Native Grasses for Recycled Water Irrigation.” University of California-Davis, Slosson Research Endowment for Ornamental Horticulture Research Report 2000-2001.

Wu, L., X. Guo, and A. Harivandi. 2001b. “Salt Tolerance and Salt Accumulation of Landscape Plants Irrigated by Sprinkler and Drip Irrigation Systems.” Journal of Plant Nutrition. 24(9):1473-1490.

Wu, L., X. Guo, and J. Brown. 2000. “Studies of Recycled Water Irrigation and Performance of Landscape Plants under Urban Landscape Conditions.” University of California-Davis, Slosson Research Endowment for Ornamental Horticulture Research Report 1999-2000.

Wu, L., X. Guo, A. Harivandi, R. Waters, and J. Brown. 1999. “Study of California Native Grass and Landscape Plant Species for Recycled Water Irrigation in California Landscapes and Gardens.” University of California-Davis, Slosson Research Endowment for Ornamental Horticulture Research Report 1998-1999.

Wu, L., J. A. Harding, and M. A. Harivandi. 1998. “Studies of Recycled Water Irrigation and Effects of Elevated Mineral Nutrient Concentrations on Growth and Ion Uptake of Landscape Plant Species and Ornamental Grasses.” University of California-Davis, Slosson Research Endowment for Ornamental Horticulture Research Report 1995-1998.

Wu, L., J. Chen, H. Lin, P. Van Mantgem, M. A. Harivandi, and J. A. Harding. 1995. “Effects of Regenerant Wastewater Irrigation on Growth and Ion Uptake of Landscape Plants.” Journal of Environmental Horticulture. 13(2):92-96.

RDD\050590004 (CLR2820.DOC) 4-1

SECTION 4.0

Surface-water-quality Evaluation and Application

4.1 Introduction

Two reaches of the Upper SCR were identified by the U.S. Environmental Protection Agency as impaired by Cl. These two reaches are Reach 5 and Reach 6 (identified as Reaches 7 and 8 on the U.S. Environmental Protection Agency’s 303(d) list). Avocados and strawberries were identified as the most salt-sensitive crops currently grown in the Upper SCR. These crops are grown in the eastern end of Reach 4 of the Upper SCR, approximately 16 and 19 miles downstream of the Valencia and Saugus WRPs, respectively. Although strawberries and avocados are not commercially grown in Reaches 5 and 6 of the Upper SCR, there are concerns that elevated Cl levels in the river might pose a threat to the downstream, salt-sensitive crops located at the eastern end of Reach 4.

Ranges of Cl and salinity levels in irrigation water are discussed in this report. The follow-ing summary of Upper SCR surface-water salinity and Cl concentration within the impaired reaches is included to place these ranges in the context of local conditions. Information and data for this evaluation were obtained from the Districts.

The Phase 1, Task 2 Literature Review and Evaluation includes an initial phase of data evaluation for existing water quality. The Districts provided electronic copies of the historical surface-water data for Cl and TDS from several sampling sites along the Upper SCR between Fillmore and Newhall. Effluent data for Cl and TDS from Saugus and Valencia WRPs were also included.

The Upper SCR between Fillmore and Newhall includes approximately half of Reach 4 and all of Reaches 5 and 6 (see Figure 1). The locations of the surface-water sampling sites are shown on Figure 1. (All figures are located at the end of this section.)

4.2 Approach

Irrigation water for crop production is applied essentially throughout the year, depending on climatic conditions, crop production patterns, and purpose. Strawberries begin irrigation in September when planting occurs, and this continues on an as-needed basis. Frost-protection water is applied during the winter months when necessary, and irrigation water is mostly applied during the spring and summer months during the more common irriga-tion season. Therefore, in reviewing the water quality data and sampling sites, the decision was made to evaluate the entire year for applied water.

Because this surface-water-quality evaluation focuses on existing conditions, the historical data for the 11-year period from 1994 through 2004 were evaluated.

SECTION 4.0 SURFACE-WATER-QUALITY EVALUATION AND APPLICATION

4-2 RDD\050590004 (CLR2820.DOC)

Surface-water data for Cl were grouped into annual periods for the calendar years 1994 through 2004, and for TDS between 2000 and 2004.

4.3 Basin Plan Objectives

Regulatory guidance for water quality in the Upper SCR is provided by the LA Water Board. The current Santa Clara Watershed Basin Plan (Basin Plan) (Water Quality Control Plan, Los Angeles Region, June 13, 1994) objectives for the Upper SCR between Fillmore and Bouquet Canyon Road, approximately half of Reach 4, Reach 5, and Reach 6 (see Figure 1), are provided in Table 3-8, “Water Quality Objectives for Selected Constituents in Inland Surface Waters,” of the Basin Plan.

Basin Plan objectives for Cl and TDS are as follows:

Cl – 100 mg/L TDS – 1,300 mg/L

The water quality data for the past 5 years were assumed to best represent the existing conditions of the surface water used for crop irrigation through direct diversion.

4.4 Upper Santa Clara River Sampling

The sampling sites at the Los Angeles and Ventura County line (called “Blue Cut”) and a District site 1 mile downstream of Blue Cut (called “Station RF”) were used to describe the existing water quality (Cl and TDS, respectively) of the Upper SCR in Reach 4 near Piru.

According to Blue Cut station data, the Cl concentration appears to be increasing slightly over time and exceeds the Cl Basin Plan objective (100 mg/L) for the Upper SCR in Reach 4 in most cases (see Figure 2). These concentrations also likely exceed threshold levels for avocado production, as has been discovered in the literature to date and explained in this report.

The TDS concentration ranges between 800 and 1,100 mg/L and lies within the Basin Plan objective of 1,300 mg/L at a location about 1 mile downstream of the Blue Cut site (see Figure 3).

4.5 Water Reclamation Plants

The Saugus and Valencia WRP data for TDS were used to describe the inputs to the Upper SCR from the two tertiary WRPs. The Districts provided no data from the WRPs for Cl. Saugus WRP is the most upstream plant, and Valencia WRP is about 3 miles downstream. The data presented are for the calendar years 2000 through 2004.

The TDS concentrations for the Saugus WRP range between 600 and 800 mg/L over the last 5 years (see Figure 4). The TDS concentrations for the Valencia WRP range between 700 and 900 mg/L (see Figure 5). According to the past 5 years of record, there appears to be no substantial difference in the TDS concentration from the two WRPs. However, the TDS effluent from the Valencia WRP seems to have about a 100-mg/L greater concentration than the Saugus WRP.

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RDD\050590004 (CLR2820.DOC) 5-1

SECTION 5.0

Summary of Recommendations for Chloride Thresholds

5.1 Summary of Recommendations for Avocados

The most reasonable type of threshold that can be determined from the literature presented above is a Cl hazard level, or concentration of Cl in irrigation water at which Cl injury in avocados could, but does not necessarily, occur. The following discussion relates to the Cl hazard level for Mexican-rootstock avocados.

No evidence indicates that the Cl hazard level is below 100 mg/L. No scientific studies or extension specialists with experience in the Upper SCR have suggested that Cl injury occurs below 100 mg/L. Therefore, the lower limit of the Cl hazard range is reasonably certain.

The upper range is less certain. Above this concentration, the Cl hazard level has been interpreted up to 178 mg/L. There is reason to believe this upper value (proposed by Bingham et al. [1968]) is too high for the following reasons:

No other studies, sources of data, or documentation of experiential knowledge corroborate this value. One study (or even two) is not enough evidence on which to base a Cl hazard level.

The study was performed on sand cultures in a controlled environment and does not represent commercial field conditions. Although it is valuable as a sand-culture study, field studies are necessary to substantiate its findings.

The interpretation of the data by other researchers is different than that of the authors who conducted the study. Therefore, the conclusions from the study are not consistent with other findings.

The type of Cl salts used in the study were variables that were not addressed by the authors, but likely influenced the outcome of the study. The Ca and magnesium salts used in the study likely raised the Cl concentration at which Cl injury would have occurred if Na salts were used.

Reviewed sources that consider both local conditions (Grattan and Oster, 2002) and non-site-specific conditions (Maas, 1990 and Ayers and Westcot, 1985) recommend Cl hazard levels for Guatemalan and West Indian rootstocks that approximate or are below this value; however, these rootstocks are well known to be more salt tolerant than Mexican rootstocks.

Therefore, it is reasonable to propose that the upper limit of the Cl hazard range is lower than 178 mg/L. At Cl concentrations between 120 and 178 mg/L, Cl injury has been demonstrated to occur in several studies. For this reason, the recommendations for the Cl thresholds that are above 100 mg/L converge on 120 mg/L (approximately). The

SECTION 5.0 SUMMARY OF RECOMMENDATIONS FOR CHLORIDE THRESHOLDS

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applicability of this value has some limitations, because it is derived from sources that are not specific to the Upper SCR. However, no valuable evidence suggests another proposed Cl level anywhere between 120 and 178 mg/L.

Although there is clearly not enough evidence to propose an absolute threshold with the literature presently available, the best estimate of a Cl hazard concentration ranges from 100 to 120 mg/L. Below this range, no evidence shows that Cl injury occurs in avocados. Beyond this range, Cl injury has likely already begun to occur. This range is likely the result of uncertainty caused by natural variability in avocado populations, management practices, and interactions with other ions that either augment or diminish the toxic effects of the Cl ion. To reiterate, Cl injury in avocados of Mexican-race rootstock is possible in this range, depending on irrigation water quality, management practices, and site conditions.

The certainty of the lower limit of the range is enhanced by support from experience of local conditions in the Upper SCR and surrounding areas, documented by UCCE agents and agricultural consultants. The uncertainty of this lower limit arises from the lack of controlled and well-documented studies that explicitly confirm this value. The certainty of the upper limit of this range, on the other hand, is a result of recommendations from documented sources and studies; whereas, the uncertainty is a result of the lack of site specificity to the Upper SCR.

5.2 Summary of Recommendations for Strawberries

The conclusions drawn in these articles pertain to specific strawberry varieties and study conditions. Because of changing production practices and study locations, these vary widely for the specific conditions in the Upper SCR. Although these studies provided valuable information about strawberry Cl uptake and did correlate increased uptake with increased leaf burn, they did not provide sufficient data to determine an appropriate Cl threshold for irrigation water.

The primary factors that lead to this conclusion are as follows:


The studies noted variability in plants or plant injury to control treatments, suggesting potential outside factors in the results.

Study applicability to the Upper SCR was limited primarily with respect to the following factors:

Varieties grown

Different or unknown irrigation methods Different or unknown irrigation management Different or unknown climate Different or unknown cultural practices

SECTION 5.0 SUMMARY OF RECOMMENDATIONS FOR CHLORIDE THRESHOLDS

RDD\CLR2820.DOC 5-3

5.3 Summary of Recommendations for Nursery Crops

It is reasonable to conclude from this review of the available information that there is a lack of sufficient evidence upon which to base a recommendation for a Cl threshold. The primary factors that lead to this conclusion are as follows:

Studies by Wu et al., came the closest to providing the needed information, but they showed evidence of adverse effects with sprinkler irrigation at 300 mg/L Cl, suggesting that the threshold value is lower than 300 mg/L. However, data were not sufficient to determine how much lower the standard should be. If all drip irrigation were used for all nursery crop production, it appears that a higher threshold might be justified according to these studies. It is also difficult to justify establishing a standard based on the results of only a few experiments by one research group.

The USSL studies provided a wealth of information on the relative salt tolerance for soil-planted and surface-irrigated plants, but included no information on sprinkler irrigation effects. Given the importance of sprinkler irrigation to Upper SCR nursery crop produc-tion, and the differential effects of root zone as compared to foliar exposure, the value of these studies in setting an irrigation water standard is limited.

Thresholds suggested by extension pamphlets and local experts are not clearly tied to experimental data, making it difficult to justify expenditures of substantial funds to meet the low values suggested.

Production of nursery crops in large containers (specimen trees) is a large component of the industry, and no data are available on Cl standards for the production of these crops. In addition, a huge array of plants is potentially important to the industry, and data were only available on a limited number of species.

Appendix A Field Notes

RDD/050550003 (CLR2818.DOC) A-1

Field Notes: Avocado Production

Name and Location: Brokaw Nursery, Saticoy, California (eastern edge of Ventura)

Communication Type: Site visit

Interviewee: Rob Brokaw

Interviewer: Jim Jordahl/CH2M HILL

Date: January 19, 2005

Overall Operation

The main crops Brokaw Nursery grows are avocado, citrus seedlings (lemons, oranges, mandarin oranges, and occasionally grapefruit), and kiwi vines. They have been in operation at this site for about 30 years, but will be soon forced to move because of encroaching development. In addition to finding a new location, one major concern they have is looming regulations regarding discharge of irrigation return flow.

General Comments Regarding Chloride

The nursery does not consider chloride to be a significant problem at this point, in that they are able to manage irrigation so that symptoms do not appear before normal leaf drop. They do not consider chloride content of their irrigation water to be as big an issue as it is in areas that use other water sources.

Chloride is not something they think about in their operation, and they do not consider it to be a particular problem. Rather, they look at overall salinity and manage this through irrigation. In the future, they envision that their liberal use of irrigation water will be curtailed and the salinity problem will become much more difficult to manage. Chloride will be a part of this management challenge but it will not be the central focus unless the chloride proportion increases. They expressed concern that if the new human populations upstream all install water softeners that they would be in a “very tough situation.”

Influent Water Quality

They consider their well water to be of marginal quality for the crops they grow, and they report that other growers are surprised that they can succeed. The electrical conductivity (EC) of their well water is 1.7 to 1.8 deciSiemens per meter (dS/m), with about 63 milligrams per liter (mg/L) chloride. The “poor” water results in the need to keep the root zone relatively wet and to use a high leaching fraction. After they add fertilizer to the flow, the EC ranges from approximately 2.4 to 2.5 dS/m. They add sulfuric acid to their water to lower the pH.

Table 1 is a well-water analysis the nursery provided.

FIELD NOTES: AVOCADO PRODUCTION

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TABLE 1

Well-water Analysis Field Notes Regarding Avocado Production

Parameter Units Well Water With Fertigation

Calcium mg/L 139 139

Magnesium mg/L 40 45

Potassium mg/L 4 43

Sodium mg/L 98 113

Chloride mg/L 62.8 63.1

Total Alkalinity mg/L (assume as calcium

carbonate)

258 76.2

EC dS/m 1.72 2.39

PH Standard Units 7.8 6.4

Citrus

Citrus seedlings are grown in a greenhouse in tubes that are approximately 2 inches by 8 inches. Tubes are filled with a peat/perlite mixture, and “osmocote” slow-release fertilizer is also added. A network of pipes circulates warm water underneath the plants. Plants are irrigated with a hand sprinkler approximately 2 to 3 times per week, because they have found that no other type of sprinkler system will give them the uniformity they need. There are significant differences among citrus varieties in tolerance to sodium/chloride in sprinkler irrigation. With the water quality they have available and the citrus varieties they grow, they have not seen evidence of foliar toxicity.

Avocados

The major rootstock clones they use, in decreasing proportion, are Toro Canyon, Dusa (Merensky 2), and Duke 7. The scion variety is primarily Haas.

Greenhouse Procedures

Avocados are started from seeds in the greenhouse. Then two grafting procedures are performed, followed by a period where they are kept in the dark to produce the final product. One graft is to a South African type. Irrigation in the greenhouse is by hand sprinkler to obtain needed uniformity. Plants are irrigated about 2 to 3 times per week, depending on the weather. Plants are grown in plastic tubes that are approximately 2 inches by 8 inches, containing a very porous peat/perlite/redwood sawdust mixture. Seeds are planted in October, and the propagation process continues through the winter.

50 Percent Sun

Plants are gradually hardened as they transition from the greenhouse to full sun. Plants are placed in an area where screens are used to obtain about 50 percent of normal sunlight.


RDD/050550003 (CLR2818.DOC) A-3

Irrigation is by hand sprinkler to obtain needed uniformity, and is applied about 2 to 3 times per week.

Full Sun

Seedlings are placed in black, plastic tubes or sleeves approximately 24 inches tall and 5 inches in diameter, open on the bottom to allow leaching. The seedlings are removed from the greenhouse media and are planted in the soil in the sleeves. The sleeves are placed on a layer of sand to prevent roots from becoming too securely anchored to the soil below the sleeves, because plants need to be moved occasionally during the production period and when they are sold. Growers (the nursery’s customers) are found along the California coast as far north as Monterey, and as far south as the Mexican border.

Seedlings are placed in full sun in March through April, and are grown for a year. The product is sold the following March. The entire process from seed to final sale of avocado seedling takes about 16 to 18 months.

The sleeves are filled with a soil mixture that they consider “dense,” which favors survival of the seedlings after they are planted in the producer’s field. The mixture consists of a mixture of redwood sawdust, mushroom compost, sand, and topsoil. Mushroom compost consists primarily of horse manure that has been used to produce mushrooms. Using a 100 percent sand media would produce plants of the desired size more quickly, but plants would do poorly after leaving the nursery and planting in the field. The salts contained in the mushroom compost are a concern, but they feel that it is an important soil amendment for their operation.

Irrigation is by drip, with one dripper per sleeve. Uniformity of avocado seedlings is an important attribute, and they work hard to achieve this. They have seen that flow decreases slightly along each run, and have considered feeding the flow from both ends to improve uniformity.

They generally irrigate during the day, in part because, inevitably, things break at night when nobody is available. Irrigation scheduling is a judgement (“an art”), and is not based on the California Irrigation Management Information System or other predictive tools. They apply approximately 1 gallon per irrigation per pot in four “pulses,” which consists of the following: an initial wetting, waiting an hour, a first irrigation pulse, waiting an hour, a second irrigation pulse, waiting an hour, then application of a final leaching pulse. They feel that pulsing the water achieves better leaching of salts. They estimate that they apply approximately 30 to 40 percent additional water to leach excess salts. Fertigation is applied during the two irrigation pulses. Drainage (irrigation return flow) is collected in a ditch that runs along the ends of the rows.

Other Crops

They have tried to grow an exotic Chinese fruit called lychee (Litchi chinensis), but the quality of their well water will not allow it.


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Recommendations from Soil and Plant Laboratory

Mr. Brokaw provided some recent reports and recommendations from Bill Darlington at the Soil and Plant Laboratory:

Boron and sodium continue to be present at relatively high levels.

All nurseries will need to curtail nutrient and water runoff in the near future.

Soluble salts of influent water are moderately high.

A number of nurseries use a water collection and reuse system. Depending on water quality, the water may be used to irrigate perimeter plantings, a subset of salt-tolerant plants, or may be filtered, blended with fresh water, fortified with nutrients, and reapplied in the nursery.

Watershed Considerations

Nearly all water used for irrigation in the watershed is from groundwater, as the river is not a reliable supply, especially in the summer when water is needed most. Frank Brommenschenkle, a Santa Paula-based consultant, is known as an expert in water supply issues in the area.

They believe that increases in irrigation water salinity would be more of a limitation to citrus than avocado in the watershed, because of the rootstocks that are used. If the quality of their well water decreases, they note that the discharge of their drainage or return flow will also be of lower quality (higher salinity), which will be increasingly problematic as regulations on discharge become more strict.

Avocados in the watershed are first established with drip irrigation for the first 6 to 14 months, and are then maintained using mini sprinklers. Fertigation is standard, and mulching with yard waste and compost is increasingly common.

Avocado rootstocks are either salt resistant or phytophthora resistant, but no varieties are known that are resistant to both. Phytophthora is generally the major hazard, but they can envision that being replaced by salinity concerns.

RDD/050550003 (CLR2818.DOC) A-5


Name and Location: Grower, Piru, California

Communication Type: Telephone conversation

Interviewee: Don Shram

Interviewer: Stephanie Tillman/CH2M HILL


Conversation Details

Don Shram provided the following information about his practices:

Shram operates 2.5 acres of avocados, 1 or 2 years old.

Shram has managed other avocado and citrus orchards.

Shram is a beekeeper and has pollinated other people’s orchards using his bees.

Shram uses sprinkler irrigation – solid set.

Shram irrigates for 24 hours once every 2 weeks.

Shram grows on loam-clay loam soil.

Shram uses Duke 7 rootstocks with Hass.

Shram uses Zutano for cross-pollination; he used Bacon previously.

Every other tree on every other row is a pollinator; the pollinator tree is opposite flower type to whatever is in the grove. The trees are close to bees, giving trees more fruit.

Hillside groves cannot be spaced perfectly even like flat groves.

The convention was to plant at 12- to 16-foot spacing and then cut trees as the growth got too thick; the result was 24- to 30-foot spacing.

More recently, growers are planting closer and pruning back (Partida is advocating this type of pruning).

Shram plants at 24-foot spacing in 20-foot rows so he does not have to cut out trees or prune; pruning is too much work.

Citrus growers turned into avocado growers, and that is why a lot of cultural practices come from citrus practices.

Hass blooms a little late, Bacon blooms a little early, so the window for them to pollinate is narrow.


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Compatible blooming periods are very important for good fruit set.

Cool, foggy weather results in crossover, when morning flowers are still open in the afternoon.

Shram got 12,000 pounds on Lloyd-Butler Ranch when he had his bees there, an outstanding yield.

Shram thinks that 7,000 pounds per acre is a good but achievable yield.

Shram supplies at least 1 pound of nitrogen (per tree?) in growing season.

Shram used to apply all the fertilizer at once; now he fertigates using UN32 (urea, 3.5 pounds nitrogen per gallon) every other irrigation (twice per month).

Shram’s parking lot analogy: if you do not supply enough nitrogen, other elements will get there first, accumulate in excess, and cause chlorotic leaves.

RDD/050550003 (CLR2818.DOC) A-7


Name and Location: Fruit Growers Laboratory, Santa Paula and Piru areas, California

Communication Type: Meeting

Interviewee: Darrell Nelson

Interviewers: Stephanie Tillman/CH2M HILL and Joel Kimmelshue/CH2M HILL

Date: February 3, 2005

Darrell Nelson provided the following information about growing avocados in the Santa Paula and Piru areas of California:

Climate – Local microclimates are prevalent. Climate is warmer on hillslopes and farther down the valley because the elevation is lower.

Irrigation Method – All avocados are on microsprinkler. Some university publications state that drip is commonly used, but this is not true.

Irrigation Management – Irrigation is applied every 3 to 4 days for 6 to 8 hours. The leaching fraction ranges between 1 and 20 percent, but is seldom above 10 percent. One acre-foot is used on young trees, and 3 acre-feet are used on mature trees. Some growers are using considerably less irrigation (18 to 24 inches). Camulos Ranch uses 17 percent.

Soil Type – Soil is medium textured.

Rootstock – Rootstock is Duke 7 and Toro Canyon.

Variety – Variety is Hass.

Cultural Practices

Field preparation – Mulching is used to prevent root rot, but it is an expensive method.

Planting spacing – The standard is 20 feet by 20 feet, resulting in 110 trees per acre; the trend is toward more dense planting.

Thinning –

Fertilizer – Nitrogen, potassium, and zinc are used. UN32 is used for nitrogen. Potassium sulphate is used for potassium. Nitrogen is applied at 40 to 70 pounds per acre.

Pesticide control – Phosphite is used to control root rot.

Pruning –

Harvesting – Avocados are picked from late December until August.


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Pollination – Two to four beehives are on each acre. More and more bees are being used. University of California Extension recommends 5 percent pollination trees, but Nelson uses 20 percent.

Route/Rate of Exposure

Irrigation Water Quality – See comments. United Water has the data.

Seasonal Irrigation Water Quality Variation – United Water has the data.

Comments

No one knows how often to replace avocado orchards, because it is a relatively young industry. The trend is toward denser planting with more frequent turnover.

In the lower part of the valley, total dissolved solids (TDS) is around 1,200 to 1,300 parts per million (ppm), because the Piru and Sespe Creeks empty into the river, and they have relatively good water quality. The chloride is around 45 ppm.

East of the Sespe Creek mouth, the TDS is around 1,500 to 1,600 ppm.

Cold crops (vegetables) are grown east of Piru because they can tolerate higher TDS water.

Valencia orange groves are being replaced with some avocado orchards, but mostly vegetables and nursery crops.

Camulos Ranch leases out their strawberry ground to Prime Time.

RDD/050550003 (CLR2818.DOC) A-9


Name and Location: Lloyd-Butler Ranch, Saticoy, California


Interviewees: Jim Lloyd-Butler, Owner and Roger Essick, Farm Manager (also on Research Committee of California Avocado Commission)



Jim Lloyd-Butler and Roger Essick provided the following information about growing avocados in Saticoy, California:

Climate – Lloyd-Butler Ranch is 7 miles inland.

Irrigation Method – They start new trees on drip, then switch to microsprinkler after the first year or so. Drip was introduced and used a lot in the 1970s, but fell out of use not because it did not work, but because management issues were associated with it. Leaves from the trees fell and covered up the system and soil, and growers could not tell if it was working.

Irrigation Management – They use 2 to 3 acre-feet (closer to 2 acre-feet, even less if there is a lot of rain). They used to use less water, but new research found that the old crop coefficients were too low. This includes a 10 percent leaching fraction. (How often do they irrigate and for how long?)

Soil Type – Soil is medium textured. It is sandy enough to allow for good drainage.

Rootstock – Rootstock is Toro Canyon and Duke 7.

Variety – Variety is Hass.

Cultural Practices –

Field preparation – They mulch around the base of trees to promote good root environment. The roots grow up into the mulch instead of down into the soil where it can be saturated.

Planting spacing – Standard spacing was 20 feet by 20 feet or even wider, but new groves have been planted at 10 feet by 10 feet. They are also experimenting with some other spacings, such as 12 feet by 12 feet and 12 feet by 16 feet. Densely planted trees will be pruned more.

Thinning – See pruning.

Fertilizer – They apply less than 1 pound of nitrogen per tree.

Pesticide control – They use pesticide for mites, thrips, and various other pests.


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Pruning – See spacing. If the grower prunes too much, avocados will grow vegetatively and not produce enough fruit. Pruning on densely planted groves is not expected to be significantly more work than on more widely spaced groves, because the trees will not be as large and as difficult to deal with (such as big branches).

Harvesting – They make two to three picks per year from December until September.

Pollination – They use Ettinger and Zutano instead of Bacon. Pollinator trees are placed in between other trees that are regularly spaced (so a space is not taken up by them). Bees are also used, but are becoming extremely expensive.

Route/Rate of Exposure – Tip burn is evident at the end of the summer.

Irrigation Water Quality – They use both well and surface water, but do not have any data. Strawberry growers on this farm do not want to use river water any more; they want to use well water exclusively. However, they are not sure if they are concerned about total dissolved solids or chloride, or even other water quality parameters.

Seasonal Irrigation Water Quality Variation – They are not sure.

Comments

They always assumed 100 parts per million was the upper “threshold” of chloride for avocados, or at least the point where it was necessary to manage irrigation carefully.

The farm was bought in 1860 from the Mexican land grantee; therefore, the water rights from the Santa Clara River on this farm are very old. The rights extended past the point when the United Water Conservation District bought land and assumed water management responsibilities (and Freeman Diversion was built). Water for this farm is now diverted from the United Water canals from the Freeman Diversion. Taxation evolved from only rural/agricultural water users, to the whole population.

Growers need maximum production because the price of land is so high, that any small decrease in production is considered a significant loss. In fact, growers need to constantly find ways to increase their maximum production – they cannot be satis-fied with what is maximum production from one year to the next. Planting avocados costs $20/tree. Including all the preparation work, 1 year ago on this farm, a 6.5-acre grove cost $60,000-$70,000 to plant. Therefore, existing conditions are not static; they are changing all the time because production always needs to increase.

Avocado culture/growers have been slow to adopt high-density planting, compared to other trees.

RDD/050550003 (CLR2818.DOC) A-11


Name and Location: Newhall Land Company (east of Piru and north of Highway 126), California


Interviewee: Chris Perez



The following is a summary of information Chris Perez provided about Newhall Land Company (Newhall) avocado production.

Newhall does not grow any avocados except for one small 0.5-acre test plot that is east of Piru and north of Highway 126. They originally planned this plot as an experiment to test the feasibility of growing avocados; however, Perez is not sure of the details because it was begun before he began working at Newhall. The avocados were being irrigated from water diverted from the river; however, the recent storms destroyed infrastructure, and now they are attempting to keep them alive with well water. The avocados are only approximately 1 year old since planting, and they have suffered a lot of wind damage from the recent storms. They are being managed as citrus groves are managed, or with practices that are consistent with those of the surrounding area. No new techniques are being used because the ranch manager for Newhall (Jesse Gomez) has background in citrus culture (not avocado culture), and therefore uses the practices of the area, or those similar to citrus culture.

It is unlikely that avocado land will be leased out to tenants because the leases for tree crops must be several years, and that is considered too long by Newhall.

All of the water for irrigation comes from wells. They are reasonably close to the river, and Perez guesses that the well water is tied underground to the aquifer that is replenished by river water, although he does not know that for sure. When the wells are drilled, a feasi-bility test for crops is done on the well water by a laboratory to determine if the water is suitable for growing certain crops. Perez does not know if feasibility was considered for avocados when the present wells were drilled. Any diverted water they have used has been used for pasture.

The only land that Newhall manages itself is lemons and oranges, because they do not want to lease out land in long-term leases. The big demand for leased land in the area is for vegetable crops and nurseries. They lease out 600 acres to vegetable row crops in Ventura County and 300 acres in Los Angeles County.

They also have two nursery tenants: Valley Crest Tree Company and Pacific Coast Nursery. Valley Crest leases land from Newhall approximately 2 miles west of the Ventura-Los Angeles County line, and Pacific Coast operates on land that is closer to Piru.


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Last year, Newhall had a tenant that grew 25 acres of strawberries. The tenant discontinued the lease because the large fluctuations in temperature were not ideal for strawberry production. Water quality was not a problem.

Perez does not believe that the ranch manager or Newhall, in general, can provide valuable information about avocado cultural practices because they concentrate on managing citrus, and know little about avocado culture. He suggested the surrounding practices were a better measure of typical practices.

RDD/050550003 (CLR2818.DOC) A-13


Name and Location: University of California Cooperative Extension (UCCE), California


Interviewee: Ben Faber



Introduction

Ben Faber is the UCCE subtropical agriculture specialist for San Luis, Santa Barbara, and Ventura Counties.

Questions and Answers

Question: Do you know if there are water quality differences between the areas east of Piru and west of Piru, and if so, do growers manage their irrigation differently to account for those differences in water quality?

Response: Good question. The groundwater irrigation source wells are highly variable in Ventura County. For example, west of Fillmore, the well water typically contains a lot of nitrogen, but east of Piru, the well water typically contains very little nitrogen. A lot of boron seems to come from Sespe Creek, but the wells at Camulos Ranch, for example, have very little boron.

Question: What leaching fraction do growers typically use to irrigate avocados?

Response: I don’t know. Most growers don’t know what their leaching fractions are. Irrigation management is their last priority. First, they are concerned with arranging labor and complying with various regulatory agencies. Their irrigation management is based on tradition on their farm, best guesses, and convenience. They do not use specific methods to figure out how much water to apply and when. Generally, they turn the water on for, say, 12 or 24 hours, and leave it on, because this creates a convenient irrigation schedule. How often this occurs varies from grower to grower.

Question: Is the 100-parts-per-million chloride hazard guideline that UCCE specialists have been recommending for avocados for several years based on experience or does it come from one particular study that determined this value?

Response: If you look back at the old literature from the 1950s, you will find this value.


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Question: The literature from that time period records the experience of UCCE specialists and researchers, but no specific scientific study with data to support this value has been found in that literature. Is this the literature you are referring to?

Response: Yes. The problem is, determining an exact value would take a 10-year, full-scale, extensive study, which no one is willing to fund. This would be required because of variability in production, weather from year to year, etc.

Question: I have read that excessive chloride in irrigation water can be managed by increasing leaching. I have also read that overapplying poor-quality water can increase the constituents of concern in the soil. Which is truer in your experience?

Response: The first one is true. The only way to deal with poor-quality irrigation water, whether it contains excessive amounts of chloride, sodium, or salinity in general, is to leach. This is because the soil water can never be any better quality than the irrigation water that is used to irrigate it. In Israel, pulse irrigation is being used to decrease soil salinity. In this case, they irrigate twice a day.

Question: Do growers in the project area apply more water, more water more often, or the same amount of water more often to leach?

Response: I don’t know. No irrigation system is 100 percent efficient. This means that you always have some leaching fraction because there is some water that doesn’t reach the plant, especially in this area because growers commonly leave their irrigation systems running for 24 hours. A lot of the soils can only absorb, say, 10 hours of irrigation. This means they are applying very high leaching fractions.

Question: Does irrigation typically occur during the winter?

Response: Hopefully, growers irrigate during dry winters. They “play it by ear” because the weather is so variable here from year to year.

Question: We have heard from some growers that leaf burn always occurs to some extent at the end of the growing season. Is this true in your experience?

Response: In dry years, it is common to see leaf burn before flowering in February and March. It is also common to see it in August and September at the end of the summer irrigation season.

Question: Is this caused by a change in water quality that occurs during certain times of the year, or by accumulation of chlorides in leaves that is inevitable?

Response: Both. At the end of the summer irrigation system, wells can get drawn down into poorer quality water. Accumulation also occurs regardless of water quality. Poor manage-ment contributes a lot to this scenario, because most growers are guessing at how to irrigate. If you see a lot of leaf burn, then you know you need to change your management.


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Question: We only observed microsprinkler irrigation being used on avocados. Is drip irrigation used as well?

Response: There is less and less drip irrigation used on avocados, but there is still some. Some growers use drip on avocados for the first year after planting.

RDD/050550003 (CLR2818.DOC) A-17


Name and Location: Matt Freeman, Camulos Ranch, Piru, California


Interviewee: Matt Freeman/Camulos Ranch; also present at the meeting were Larry Eddings/Pacific Gold Farms (past strawberry lessee on Camulos Ranch) and Rob Roy/Ventura County Agricultural Water Quality Coalition

Interviewer: Joel Kimmelshue/CH2M HILL

Date: August 23, 2005

Background Information and History

Camulos Ranch has existed since the late 1880s as an irrigated farm. A wide variety of crops are grown on the ranch including strawberries, avocados, peppers, citrus, and onions.

The ranch frequently uses a river diversion for part of the year. At other times of the year, high flows in the river wash out the earthen diversion. Camulos Ranch receives necessary permits from agencies (e.g., California Department of Fish and Game) to construct the earthen diversion when needed.

The surface-water diversion is a more cost-effective irrigation water source than ground-water because of the pumping depth and associated cost for groundwater wells relative to booster pumps for surface water. The surface diversion is approximately 4 miles north of the ranch. When in place, the earthen diversion channels water into a concrete structure that then leads to a network of underground piping serving the ranch. The diversion has to be replaced annually. Portable booster pumps and filters are used throughout the ranch, in addition to some stationary booster pumps, to lift water to various fields for irrigation. Matt Freeman said, “on average, two-thirds to three-quarters of all water used for irrigation on Camulos Ranch comes from the surface diversion.”

At the time of the interview, the surface diversion had yet to be constructed for the year because of continued flows in the river following the excessively wet winter and spring coupled with releases from upstream reservoirs. Mr. Freeman did not show the interviewer the surface diversion structure for this reason and was concerned that the wrong impression would be made without the diversion in place. Mr. Freeman was expecting to construct the surface diversion in the next 2 months, after the flows in the river have dissipated enough to allow for construction. He invited the interviewer back for viewing at that time. Mr. Freeman is also considering inviting the Regional Water Quality Control Board and other interested parties for a viewing of the diversion when operative, but has yet to make that decision.

Camulos Ranch also has groundwater wells that are used as an irrigation water source during times when surface diversion is not operative. The depth of these wells can be as


A-18 RDD/050550003 (CLR2818.DOC)

shallow as 150 to 175 feet or as deep as 500 to 600 feet. Cost to pump water from this depth is more expensive than surface-water diversion; therefore, surface-water diversion is used as much as possible.

Avocado Production on Camulos Ranch

Avocado production has been conducted on Camulos Ranch for nearly 60 years. A 12-acre orchard exists that has been in production for approximately that duration. This orchard contains many varieties of avocado; however, most are on Mexican rootstock. Another 60-acre orchard is about 3 to 4 years old. The goal of Camulos Ranch is to have 150 to 200 acres of avocados in the future. Mr. Freeman said that “diversity of agricultural production and crop type on Camulos Ranch is essential to a sustainable farming operation, and avocados are an essential part of that.” He was hired as ranch manager, partly, to provide that diversity.

The avocado trees on Camulos Ranch “commonly have tip burn” (see photographic docu-mentation provided to the interviewer by Mr. Freeman). In addition, Mr. Freeman said that he believes the citrus trees are also experiencing burn and yield loss because of unsuitable irrigation water quality. At the time of the site visit, the avocado trees on Camulos Ranch essentially did not have leaf-tip burn. It was mentioned that “very little leaf tip burn was visible at this time due to the excessive leaching provided by the winter and spring rains of this past year.” However, older leaves (<1 year old) did show signs of past leaf-tip burn.

One hundred seventeen acres of avocados were recently planted in Piru Canyon owned by Rancho Temiscal.

Mr. Freeman indicated that in his experience “most people actually under-irrigate avocados.” Applied water for avocado irrigation in the area can range from “3 to 5 feet,” but mostly on the lower end of this range.

In general, avocado production on Camulos Ranch does not vary significantly from other areas visited with respect to irrigation method and cultural practices.

Avocado Field Note Attachments

Ventura County

Agricultural Commissioner

Annual Crop Report

2004

On the web: vcag.us Ventura County Page ii

Office of

AGRICULTURAL COMMISSIONER P.O. Box 889, Santa Paula, CA 93061

815 East Santa Barbara Street Telephone: (805) 933-3165

(805) 647-5931 FAX: (805) 525-8922

July 20, 2005

TO: THE HONORABLE BOARD OF SUPERVISORS OF

COUNTY OF VENTURA

STEVE BENNETT District 1

LINDA PARKS District 2

KATHY LONG, Chair District 3

JUDY MIKELS District 4

JOHN FLYNN District 5

And

A.G. Kawamura, Secretary

California Department of Food and Agriculture

Pursuant to Section 2279 of the California Food and Agricultural Code, I hereby submit the Ventura County Annual Crop and Livestock Report for 2004.

The estimated gross value for Ventura County agriculture for calendar year 2004 is $1,389,452,000. This is an overall increase of $271,824,000 from 2003. This report reflects gross values only and does not represent the net return to growers.

Highlights of the 2004 Crop Report are as follows:

Strawberries are, once again, the leading commodity in 2004 with a value of $363,646,000.

Vegetables crop value increased by $55,771,000.

Fruit and nut crops value increased by $148,372,000.

I wish to thank all the individuals, producers, processors, and government agencies whose cooperation and assistance contributed to preparing this report. I would also like to thank my department staff for their efforts in compiling and finalizing this report, especially Deputy Agricultural Commissioner, Kerry DuFrain.

Respectfully submitted,

W. Earl McPhail Agricultural Commissioner County of Ventura

WEM/lh:My Documents/Crop Reports/VC Crop Report 2004

Agricultural Commissioner

W. Earl McPhail

Chief Deputy

David B. Buettner

Page iii Ventura County On the web: vcag.us

Office of the

AGRICULTURAL COMMISSIONER

W. Earl McPhail – AGRICULTURAL COMMISSIONER

CHIEF DEPUTY AGRICULTURAL COMMISSIONER:

David B. Buettner

DEPUTY AGRICULTURAL COMMISSIONERS:

Kerry L. DuFrain Susan L. Johnson Alan D. Laird

CLERICAL:

Deanna Bowling Lidia Harrison Bernice Muñoz

FIELD STAFF:

SUPERVISING AGRICULTURAL BIOLOGISTS:

Gayland C. Hagy David Van Epp

AGRICULTURAL BIOLOGISTS:

Herb Bunch, John Calderwood, Tom Dimock, Tina Dwyer Eliseo Hernandez, Freddi Hermann, Ellen Kragh, Rudy Martel, Dexter McDonald

George Mendoza, Daniela Nekic, Louis Ortali, Bruce Spiller

AGRICULTURAL PLANNER:

Audrey Knight

INSECT DETECTION SPECIALISTS II:

Jake Baldwin Linda Bellamy

INSECT DETECTION SPECIALISTS:

Trapping: Clifford Ball, Becky Battleson, Francisco Hernandez,

Amado Mijares, Barbara Miller, Jose Muñoz, Thomas Paul, Marvin Stidham, John Salzwedel, John Sudtelgte

Inspections: Carmen Buford, Meredith Crisman, Douglas Crissman, Virginia Feyh,

Chad Hurd, Graham Jensen, Gary Johnson, Danny McDougald, Miriam Mullins, Connie Ratner, Gayle Reed, Ingus Richters, David Soriano, Dale Vesper

Ventura County On the web: vcag.us

AGRICULTURAL CROP REPORT

Recapitulation and Index

2003 – 2004

CROP GROUPING YEAR $ VALUE1

1. FRUIT AND NUT CROPS 2004 $740,039,000

Page #4 2003 591,667,000

2. VEGETABLE CROPS 2004 354,514,000

Page #5-6 2003 298,743,000

3. NURSERY STOCK2 2004 222,214,000

Page #7 2003 173,262,000

4. CUT FLOWERS 2004 65,663,000

Page #8 2003 44,515,000

5. FIELD CROPS 2004 2,270,000

Page #8 2003 3,108,000

6. LIVESTOCK AND POULTRY 2004 1,942,000

Page #9 2003 2,126,000

7. APIARY PRODUCTS 2004 362,000

Page #9 2003 1,339,000

8. TIMBER 2004 71,000

Page #9 2003 61,000

9. SUSTAINABLE AGRICULTURE 2004 2,377,000

Page #10 2003 2,807,000

GRAND TOTAL 2004 $1,389,452,000

2003 $1,117,628,000

1 Figures are rounded off to nearest $1000 2 Includes Cut Christmas Trees

On the web: vcag.us Ventura County Page 2

Five Year Comparison Of

Ventura County Crop Values

2000 2001 2002 2003 2004

Fruit and Nut Crops 473,683,000 511,167,000 631,018,000 591,667,000 740,039,000

Vegetable Crops 357,929,000 309,423,000 304,020,000 298,743,000 354,514,000

Livestock and 2,709,000 2,827,000 2,423,000 2,126,000 1,942,000 Poultry Products

Apiary Products 845,000 591,000 863,000 1,339,000 362,000

Nursery Stock 156,053,000 171,651,000 173,896,000 173,262,000 222,214,000

Cut Flowers 48,775,000 51,717,000 40,349,000 44,515,000 65,663,000

Field Crops 3,808,000 3,176,000 3,628,000 3,108,000 2,270,000

Timber 74,000 78,000 69,000 61,000 71,000

Biological Control 3,252,000 3,084,000 3,039,000 2,807,000 2,377,000

GRAND TOTAL $1,047,128,000 $1,053,714,000 $1,159,305,000 $1,117,628,000 1,389,452,000

$464

$484

$500

$508

$476

$581

$552

$613

$669

$786

$806

$853

$910

$725

$848

$852

$922

$852

$942

$937

$1,059

$1,047

$1,054

$1,159

$1,118

$1,389

0 200 400 600 800 1000 1200 1400

Value in Millions of Dollars

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Total Crop Values 1979-2004


TEN LEADING CROPS

FOR 2004

RANK CROP VALUE

1st Strawberries $363,646,000 2nd Nursery Stock 221,999,000 3rd Lemons 176,361,000 4th Avocados 124,661,000 5th Celery 122,832,000 6th Tomatoes 71,735,000 7th Cut Flowers 65,663,000 8th Raspberries 48,586,000 9th Peppers 34,628,000 10th Valencia Oranges 20,525,000

20.525

34.628

48.586

65.663

71.735

122.832

124.661

176.361

221.999

363.646

0 50 100 150 200 250 300 350 400

Value in Millions of Dollars

Valencia Oranges

Peppers

Raspberries

Cut Flowers

Tomatoes

Celery

Avocados

Lemons

Nursery Stock

Strawberries

2004

2003

2002

2001

OTHER MILLION DOLLAR CROPS

Greens 14,376,000 *Orchids 3,964,000 Lettuce 11,947,000 Parsley 3,949,000 Cabbage 10,628,000 Carrots 3,189,000 Spinach 9,538,000 Kale 2,786,000 Cilantro 7,946,000 Oriental Vegetables 2,558,000 Radishes 7,059,000 Navel Oranges 2,229,000 Broccoli 6,704,000 Livestock 1,942,000 Beans (all) 5,991,000 *Poinsettia 1,664,000 Onions (all) 5,699,000 Sweet Corn 1,321,000 *Veg. Transplants 5,327,000

* Included in Nursery Stock total above


FRUIT AND NUT CROPS

ACREAGE, PRODUCTION AND VALUES 2003-04

PRODUCTION $ VALUE

HARVESTED PER PER CROP YEAR ACREAGE ACRE TOTAL UNIT UNIT TOTAL

AVOCADOS 2004 19,234 3.28 63,095 Tons $1,975.78 $124,662,000 2003 17,545 2.74 48,024 “ 2,098.12 100,760,000

GRAPEFRUIT Total 2004 75 17.73 1,330 “ 378.20 503,000 2003 103 8.03 827 “ 276.91 229,000

LEMONS Total 2004 22,520 15.39 346,601 “ 508.83 176,361,000 2003 23,865 17.17 422,898 “ 351.47 148,634,000

ORANGES (Navel) Total 2004 501 7.97 3,991 “ 558.51 2,229,000 2003 755 7.81 5,892 “ 316.88 1,867,000

ORANGES (Valencia) Total 2004 5,426 10.12 54,935 “ 373.62 20,525,000 2003 5,315 14.24 75,660 “ 253.19 19,156,000

RASPBERRIES 2004 1,477 11.53 17,034 “ 2,852.30 48,586,000 2003 372 7.47 2,777 “ 6,370.91 17,692,000

STRAWBERRIES Total 2004 10,349 26.41 273,312 “ 1,330.49 363,646,000 2003 8,794 30.48 268,041 “ 1,122.02 300,746,000

Fresh 2004 170,705 “ 1,833.71 313,023,000 2003 177,817 “ 1,425.48 253,473,000

Processed 2004 102,612 “ 493.34 50,623,000 2003 90,224 “ 523.96 47,273,000

TANGERINES & 2004 148 3.2 474 “ 1,734.18 822,000 TANGELOS

MISC. FRUITS 2004 460 “ 2,705,000 AND NUTS3 2003 615 “ 2,583,000

TOTAL 2004 60,190 $740,039,000 2003 57,364 $591,667,000

3 MISC. FRUITS AND NUTS include Apples, Apricots, Asian Pears, Bushberries, Cherimoya, Grapes, Guavas, Kiwi, Limes, Persimmons, Macadamias, Tangelos, Tangerines, Walnuts; and miscellaneous citrus, deciduous, and subtropicals


VEGETABLE CROPS


PRODUCTION $ VALUE


BEANS Green and Dry Limas, 2004 3,064 2.31 7,080 Tons 846.19 $5,991,000 Green Snap 2003 2,073 1.99 4,112 “ 544.51 2,239,000

BROCCOLI Fresh and 2004 1,348 7.64 10,301 “ 650.81 6,704,000 Processed 2003 2,775 7.81 21,646 “ 609.26 13,188,000

CABBAGE 2004 2,213 20.81 46,063 “ 230.73 10,628,000 2003 2,134 25.53 54,465 “ 177.92 9,690,000

CELERY 2004 11,249 39.55 444,867 “ 276.11 122,832,000 2003 11,030 39.75 438,359 “ 258.65 113,381,000

CILANTRO 2004 1,614 8.92 14,397 “ 551.92 7,946,000 2003 1,328 7.35 9,760 “ 574.39 5,606,000

CUCUMBERS 2004 127 8.86 1,125 “ 824.89 928,000 2003 149 10.67 1,589 “ 724.99 1,152,000

GREENS4 2004 1,603 - 1,623,197 Ctns 8.86 14,376,000 2003 1,644 - 1,683,546 “ 8.69 14,619,000

KALE 2004 322 9.61 3,093 Tons 900.74 2,786,000 2003 159 15.92 2,531 “ 668.91 1,693,000

LEEKS 2004 136 8.67 1,179 Tons 1,765.90 2,082,000

LETTUCE 2004 2,306 12.52 28,881 “ 413.66 11,947,000 Total 2003 2,199 11.17 24,544 “ 457.84 11,237,000

Head 2004 311 18.49 5,749 “ 266.48 1,532,000 2003 235 12.90 3,030 “ 334.33 1,013,000

Romaine 2004 1,155 13.42 15,499 “ 394.09 6,108,000 2003 980 12.91 12,650 “ 431.55 5,459,000

Leaf 2004 840 9.09 7,633 “ 564.26 4,307,000 2003 984 9.02 8,874 “ 536.97 4,765,000

4 Includes: chard, collard, mustard, turnip and watercress.


VEGETABLE CROPS


PRODUCTION $ VALUE


ORIENTAL VEG. 2004 627 6.88 4,311 Tons 593.37 $2,558,000 2003 630 7.13 4,491 “ 801.39 3,599,000

ONIONS 2004 999 14.10 14,087 “ 404.56 5,699,000 Green & Dry 2003 699 13.17 9,202 “ 461.21 4,244,000

PARSLEY 2004 579 7.96 4,609 “ 856.80 3,949,000 2003 342 20.94 7,159 “ 476.47 3,411,000

PEPPERS Fresh and 2004 3,155 22.88 72,195 “ 479.65 34,628,000 Processed 2003 1,647 26.19 43,119 “ 532.58 22,964,000

PUMPKIN 2004 84 16.26 1,366 “ 187.41 256,000 2003 72 13.21 951 “ 212.41 202,000

RADISHES 2004 1,031 6.11 6,295 “ 1,121.37 7,059,000 2003 467 10.73 5,008 “ 494.81 2,478,000

SPINACH 2004 901 7.39 6,659 “ 1,432.35 9,538,000 2003 1,041 8.18 8,509 “ 726.76 6,184,000

SWEET CORN 2004 374 7.06 2,640 “ 500.38 1,321,000 2003 677 6.08 4,114 “ 335.93 1,382,000

TOMATOES5

2004 966 51.66 49,907 “ 1,437.37 71,735,000 2003 167 157.02 26,222 “ 1,775.69 46,562,000

VEGETABLES, MISC.6

Field, Indoor, and 2004 1,776 “ 31,551,000 Processed 2003 1,895 “ 34,912,000

TOTAL 2004 34,474 $354,514,000 2003 31,128 $298,743,000

5 Includes hydroponics

6 Includes: artichokes, arugula, asparagus, baby vegetables, beets, carrot, cauliflower, eggplant, endive, garlic, gourds, herbs,kohlrabi, melons, mushrooms, peas, radicchio, sprouts, squash, tomatillos, and turnips.


NURSERY STOCK

PRODUCTION AND VALUES 2003-04

PRODUCTION AREA Greenhouse Field Per ITEM YEAR PRODUCTION Square Feet Acres Unit TOTAL

NURSERY STOCK 2004 -------- -------- 7,801,452 3,861 $221,999,000 2003 -------- -------- 5,980,229 3,635 173,073,000

Fruit and Nut 2004 914,696 Trees 97 14.30 13,082,000 Trees 2003 473,056 Trees 51 12.92 6,109,000

Potted Plants 2004 4,271,607 Pots 3,808,587 34 3.58 15,300,000 2003 3,116,020 Pots 1,770,510 63 5.45 16,961,000

Propagative Mat 2004 60,078,014 Cuttings 424,030 16 .16 9,772,000 2003 87,939,580 Cuttings 308,540 9 .11 9,658,000

Herb. Perennials 2004 4,741,509 Containers 682,932 110 2.50 11,850,000 2003 5,429,550 Containers 947,962 61 2.29 12,408,000

Woody Orn. 2004 12,281,426 Tree/Shrubs 1,138,180 1,362 7.61 93,515,000 2003 10,194,728 Tree/Shrubs 956,000 1,242 6.82 69,444,000

Bed. Plants 2004 73,437,894 Flats 411,860 2,223 1.00 73,153,000 Gr. Cover & Turf 2003 58,638,344 Flats 611,540 2,167 .89 52,075,000

Veg. Transplants 2004 2,628,520 Flats 1,335,863 19 2.03 5,327,000 2003 2,895,968 Flats 1,385,677 42 2.22 6,418,000

CHRISTMAS 2004 8,344 Trees 23 25.77 215,000 TREES (CUT) 2003 7,585 Trees 36 24.92 189,000

TOTAL 2004 $222,214,000 2003 $173,262,000


CUT FLOWERS


ITEM YEAR ACRES PRODUCTION UNIT TOTAL $ VALUE

FLOWER BLOOMS & 2004 23 7,969,547 Blooms $2,099,000 STEMS 2003 13 2,326,447 “ 1,361,000

CUT GREENS & DRIED 2004 150 483,585 Bunches 577,000 FLOWERS 2003 131 1,323,158 “ 1,237,000

FLOWER BUNCHES 2004 905 29,442,642 Bunches 62,987,000 Total 2003 908 20,253,406 “ 41,917,000

Statice, Lace, Aster 2004 116 2,597,881 “ 4,776,000 And Gypsophila

Chrysanthemums and 2004 72 4,408,250 “ 5,402,000 Sunflowers

Lilies & Irises 2004 59 2,770,048 “ 12,313,000 2003 71 1,640,979 “ 6,719,000

Lisianthus 2004 32 1,286,437 “ 5,543,000 2003 32 1,179,266 “ 3,506,000

Stock, Larkspur, 2004 225 7,530,542 “ 11,501,000 Delphinium & Snapdragons

Miscellaneous 2004 401 10,849,484 “ 23,452,000 2003 297 6,598,129 “ 13,650,000

TOTAL 2004 1,078 $65,663,000 2003 1,052 $44,515,000

FIELD CROPS

ACREAGE, PRODUCTION AND VALUE 2003-04

CROP YEAR HARVESTED ACREAGE TOTAL $ VALUE

ALFALFA AND PASTURE 2004 100,360 $1,061,000 Irrigated and Non-Irrigated 2003 135,195 1,239,000

GRAIN7, HAY, FLOWER 2004 1,330 1,209,000 & VEGETABLE SEED 2003 1,239 1,869,000

TOTAL 2004 $2,270,000 2003 $3,108,000

7 Includes green barley


LIVESTOCK AND POULTRY


$ VALUE ITEM YEAR PRODUCTION UNIT PER UNIT TOTAL

LIVESTOCK Cattle, Hogs 2004 16,219 cwt. 109.75 $1,780,000 Sheep 2003 20,236 cwt. 90.88 $1,839,000

POULTRY Eggs, Ducks 2004 92,000 2003 210,000

OTHER LIVESTOCK8 2004 70,000 2003 77,000

TOTAL 2004 $1,942,000 2003 $2,126,000

APIARY PRODUCTS


$ VALUE CROP YEAR PRODUCTION UNIT PER UNIT TOTAL

HONEY 2004 155,830 lbs. $.96 $150,000 2003 757,419 lbs. 1.48 1,115,000

BEESWAX 2004 3,165 1.58 5,000 2003 5,851 2.40 14,000

POLLINATION USE 2004 207,000 2003 210,000

TOTAL 2004 $362,000 2003 $1,339,000

TIMBER


CROP YEAR $VALUE

TIMBER9 2004 $71,000 2003 $61,000

8 Deer, squab and alpaca 9 Timber harvested for lumber.


SUSTAINABLE AGRICULTURE

ITEM PEST AGENT SCOPE OF PROGRAM

BIOLOGICAL CONTROL Commercial Insectaries Red and black scale, Aphytus melinus, Estimate 1,383,692,550 Mealybug, snails, Cryptolemus, beneficials, released on various aphids mites Decollate snails, 625 ranches. and flies various predators, Valued at parasitic wasps and $2,377,000 nematodes

PEST ERADICATION Scotch Thistle Mechanical/Pulling 1 Site

PEST EXCLUSION Incoming Shipments Various Postal/UPS/Fed Express (Parcels) 8,672 Truck/Air Freight 5,700 Gypsy Moth Household Goods (Inspections) 127 Total 14,499

ORGANIC FARMING Number of registered growers 43 Vegetables Acreage 1,802 Fruits and Nuts Acreage 2,901 Field Crops Acreage 365 Flowers Acreage 3

RDD/050550003 (CLR2818.DOC) A-39

Field Notes: Strawberry Production

Name and Location: Fruit Growers Laboratory, Santa Paula, California; Upper Santa Clara River agricultural region, California


Interviewee: Darrell Nelson/Fruit Growers Laboratory

Interviewer: Mica Heilmann/CH2M HILL


Introduction

A summary of information and observations gathered during a field review of the Upper Santa Clara River agricultural region, with respect to strawberry production follows. A 1-day tour was conducted to observe strawberry production in the area of concern, and to interview local agricultural professionals regarding strawberry production practices and trends. Darrell Nelson of Fruit Growers Laboratory was interviewed.

Regional Strawberry Production Overview

The region between Santa Paula and Santa Clarita was observed. General crop production trends indicated a decline in citrus land - mostly oranges and some lemons. These lands have been replaced by avocados and vegetables and, to a lesser extent, strawberries. In general, strawberry production was sparse. Only one planting was observed in the upper Santa Clara River watershed (area of concern). Two other new plantings were observed west of the area of concern. These had both formerly been lemon orchard. A couple other areas may have had strawberries planted in the past, but are currently under vegetable production. In general, strawberry production increases toward the west of the area of concern because of a more favorable climate.

Neither interviews nor field observations indicated that strawberry production in the area of concern is increasing. Nelson said that the weather in this area is a little too warm during the summer for maximized fruit production.

Strawberry Production Practices

Strawberry lands are fumigated prior to planting. The fumigation process is typically conducted in a final planting bed preparation pass that includes application of a plastic mulch, which leaves land ready for planting. Beds were around 1 foot high and 2 to 3 feet wide with four planted rows per bed. All berries were drip irrigated with two drip-tape lines per bed. A preplant fertilizer application is usually banded in, and the remaining fertilization occurs through fertigation, based on plant needs as indicated by tissue analysis. An application of compost is usually incorporated each year before bed preparation.

FIELD NOTES: STRAWBERRY PRODUCTION

A-40 RDD/050550003 (CLR2818.DOC)

Irrigation water quality varies in the valley. All strawberries are irrigated off wells. According to Nelson, typical water quality on the north side of the valley is around 45 parts per million (ppm) chloride (Cl) and 1,600 ppm total dissolved solids (TDS), whereas quality to the south and west is around 110 ppm Cl and 1,000 ppm TDS. Nelson noted that there is more visible plant injury in the latter. He also noted that, in general, growers want TDS <1,000 ppm, Cl <100 ppm, and boron <1.0 ppm.

Strawberries are typically grown on coarser textured soils, but Nelson has noticed they are moving onto heavier textures.

Strawberry plantings typically run from July though December or October through July, although one site we visited appeared to be close to planting - probably February. Farms are usually 100 percent berries. They do not rotate into another crop.

Additional Notes

Notes about key strawberry stops follow:

Stop 1 – A new berry planting (approximately 100 acres) near Santa Paula (first year planted, previously lemons) that had probably been planted in October was observed. It is being irrigated with a new well that has approximately 110 ppm Cl, but also had high sulfate. Berries were irrigated with two drip-tape lines per four-row bed (Photo 1). Mature avocado trees growing nearby here had slight tip burn.

Stop 2 – Another new strawberry planting (also previously lemons) approximately 80 acres was along Foothill Road near Fillmore. This planting had the same irrigation and row configuration as Stop 1, but slightly heavier soils and higher (1 foot or more) beds. Plants looked a little better here, although no signs of injury were seen at Stops 1 or 2. This site has lower Cl well water. Groundwater in this area is in the 45-ppm Cl and 1,600 ppm TDS range and is high in calcium carbonate (this fact alone could offset other water quality issues).

Stop 3 – South of Highway 126 at Rancho Camulos Museum, an approximate 80-acre site that used to be berries was being prepared to plant vegetables.

Stop 4 – North of highway 126 near Camulos was the only strawberry farm evident in the area of concern at the time of observation. It was approximately 80 acres and ready to be planted in berries. Beds were formed, fumigated, and covered. Planting looked likely in the next couple of weeks. They were probably waiting for fumigation completion prior to planting. This area was surrounded mostly by vegetable land - especially peppers.


RDD/050550003 (CLR2818.DOC) A-41

PHOTO 1

RDD/050550003 (CLR2818.DOC) A-43


Name and Location: Ventura County Cooperative Extension, Ventura, California


Interviewee: Oleg Daugovish/Ventura County Cooperative Extension



Regional Strawberry Production Overview

In general, strawberry production in the Upper Santa Clara River is small. Production in Camulos, California, has increased some recently, but is still small relative to production in the Oxnard Plain, where climatic conditions are more favorable. Annual strawberry production in the Upper Santa Clara River is estimated at about 100 acres.

The primary planting season (for 80 to 90 percent of strawberry fields) is the winter season with planting in October. Planting dates have been getting earlier because growers are trying to get earliest possible production and capture the best market prices.

Strawberry Production Practices

Soils are always fumigated prior to planting strawberries. Fumigation products vary and change over time, but this year (2004/2005), about 40 percent of fields used methyl bromide, 25 percent used InLineTM, and the rest used other miscellaneous products. Methyl bromide could be used despite its ban (effective in 2005) because of an exemption received by Ventura County for this season. However, the price of methyl bromide is rising because of decreased use. Because of the rising cost, its use is decreasing, and other products that have become less expensive are being used. Compost is not typically applied for strawberries. It is applied sometimes for other crops and is usually obtained locally at a composting facility. Shoreline Organic is one local source.

Strawberry beds are formed with widths ranging from 62 to 68 inches. Two drip lines are installed per bed. Drip emitter spacing varies, but is between 6 and 12 inches.

The basis for irrigation management is climate data such as California Irrigation Management Information System or private weather stations. Growers monitor climate closely for both irrigation scheduling and disease management purposes. They use evapotranspiration requirements to determine irrigation rates and apply a leaching fraction according to Integrated Pest Management for Strawberries. Some use tensiometers. Growers apply leaching fractions according to the table provided in Integrated Pest Management forStrawberries (Division of Agricultural and Natural Resources, 1994.)


A-44 RDD/050550003 (CLR2818.DOC)

Strawberry farms run temporary (hand-move) sprinklers for 4 to 6 weeks after panting to establish the berries. The interviewee felt this was an unnecessary practice, but that growers do it because they can, and do not take any risks with this costly crop. This practice also causes a runoff problem because little applied water can infiltrate into plastic-covered beds. Water availability is a problem in the more prevalent strawberry growing region to the west, where farms rely on irrigation water delivery and not wells.

Growers use a preplant fertilizer and then fertigate throughout the growing season. Some use plant analysis to determine fertigation practices, but most fertilize using past experience and plant response.

Additional Notes

In general, Mr. Daugovish has not heard much of chloride water quality issues from strawberry growers. He felt that if they were having considerable chloride problems he would hear about it fairly quickly. He indicated that this was the case with other visible production problems.

Work Cited

Division of Agricultural and Natural Resources. 1994. Integrated Pest Management forStrawberries. Publication 335.

RDD/050550003 (CLR2818.DOC) A-45


Name and Location: George E. Brown, Jr., Salinity Laboratory, University of California Riverside, Riverside, California


Interviewee: Don Suarez/US Salinity Laboratory


Dates of Contact: March 11, 2005

Dr. Suarez was involved in earlier discussions regarding chloride sensitivity in strawberries and the Upper Santa Clara River.

During his involvement, a panel of professionals including Dr. Jim Oster indicated that strawberry responses were to salinity effects only and not chloride. Mr. Suarez objects to this claim, stating that the ion composition in previous studies is not appropriate or representative of the area water chemistry. He also indicated that other factors in that study result in questionable chloride threshold determination. His believes there is not enough evidence in literature to determine if there is a chloride threshold for strawberries.

Dr. Suarez is involved in an ongoing study at the Salinity Lab that is examining different water ion composition and the effect on strawberries. However, this study is not designed to determine a chloride threshold. This study contains three different chloride levels. Dr. Suarez stated many more chloride increments would be required to answer questions about a chloride threshold. He said when this study is completed, it will provide some useful general information but will not answer the question of chloride threshold for strawberries.

Although Dr. Suarez believes the literature does not have enough information to prove there is a chloride threshold, he suspects that there is one, and said that most salt-sensitive crops do have a sensitivity to sodium and chloride apart from salinity. Strawberries would be an exception if they did not.

RDD/050550003 (CLR2818.DOC) A-47


Name and Location: University of California – Davis, California


Interviewee: Steve Grattan, Plant-Water Relations Specialist, University of California, Davis


Dates of Contact: May 5, 2005

Introduction

Steve Grattan is a plant-water relations specialist at the University of California – Davis.

Questions and Answers

Question: We site your document as follows: Grattan, Steve. 1991. “Irrigation Management for Salinity Control in Strawberry Production.” Strawberry News Bulletin, California Strawberry Commission. April 10. What is the basis for the range given in that document of 175 to 260 milligrams per liter (mg/L) in soil-saturated extract, which would convert to 116 to 173 mg/L in irrigation water?

Response: If I quote a range, it is always based on some earlier research or literature. This range is based on the work of Gene Maas. His document that has ranges for salinity and chloride (ASA Drainage paper) was updated in 1990, and I worked with him on it. We updated some of the thresholds, but there was nothing new for strawberry. The research that produced these thresholds was done on “ancient” strawberry varieties that are no longer in use. Maas is the only source for this kind of data, and everyone uses it because he is a very respected researcher. We really do not know what the threshold is, or the exact effects of salinity and specific ion effects by themselves. There has been a lot of questioning about this subject, so Don Suarez (US Salinity Laboratory) is doing an experiment to try to determine the singular and additive effects of chloride and salinity. The experiment is not finished, and the results are not in yet.

Question: What does this range refer to, injury or yield?

Response: It refers to injury. Typically, the ranges given in the literature refer to injury, because they are likely all based on the Maas work.

Question: Why is the range so big?

Response: The size of the range accounts for different varieties.

Question: Is the difference in salinity and chloride tolerance between varieties still significant in newer varieties?


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Response: Yes, it can be. Typically, I have seen differences in salinity tolerance between varieties of 15 to 20 percent in different species. This difference in tolerance levels is usually even larger for specific ion toxicities. However, these differences are more pronounced in crops that are grown perennially, and less pronounced in crops that are grown annually.

Comment: We have articles from the literature that recommend threshold ranges that are similar but not exactly the same. For example, the ranges for irrigation water include 110 to 190, 120 to 190, and 107 to 178, which are all similar but not exactly the same as the range you cite. Some are from Australia. No sources were cited for them, so we do not know where they came from.

Response: They are likely all from the same source, which is the Maas publication based on Bernstein, and maybe Ehlig from 1958. There is no other source for this information. The ranges are likely slightly different because of rounding errors. Bernstein originally reported one significant figure, and these ranges use three significant figures, so it is likely that everyone uses different conversion factors and ends up with different numbers.

Comment: We think the threshold ranges recommended by various articles in the literature are all based on the Maas data, even though they do not necessarily cite a source, because they are all so similar.

Response: Yes, I agree, this is the only reliable source of data out there. They are based on trials where chloride was the main ion. When chloride is the main ion, we can use the conversion factor of 10 to get from electrical conductivity to chloride concentration to figure out the chloride threshold.

Question: This conversion factor is used by Maas and others in the literature and we have found nothing that refutes it or replaces it. Is it generally accepted?

Response: Yes, even though the treatments do not necessarily separate salinity effects from chloride effects, it is commonly used and gives an estimate of chloride threshold.

Question: What about the threshold value given in the Integrated Pest Management Strawberry Handbook of 140 mg/L. There is no source given for it either.

Response: That number likely came from many people conversing and deciding on a number, but it is unlikely that the threshold is just one value. The most we can do when we recommend a threshold is a range, because the point at which injury begins depends on many factors such as management.

RDD/050550003 (CLR2818.DOC) A-49


Name and Location: Larry Eddings/Pacific Gold Farms, Watsonville, California


Interviewee: Larry Eddings/Pacific Gold Farms (past lessee on Camulos Ranch); also present at the meeting were Matt Freeman/Camulos Ranch and Rob Roy/Ventura County Agricultural Water Quality Coalition

Interviewer: Joel Kimmelshue/CH2M HILL

Date: August 23, 2005

Background Information and History

Larry Eddings of Pacific Gold Farms is the president and an owner of Pacific Gold Farms. Pacific Gold Farms leases and owns ground throughout California, mostly focusing on strawberry production. They have 30 to 40 ranches as far north as the Bay Area and as far south as Southern California. Larry Eddings has been involved in production agriculture, specifically strawberry production, for decades. He has seen nearly 15 different varieties of strawberries developed over the last 25 to 30 years. Irrigation water samples are always taken by Pacific Gold Farms when developing an area for strawberries.

Strawberry Production on Camulos Ranch

Pacific Gold Farms conducted strawberry production on Camulos Ranch for 2 years. A summary of that production is described in a letter to Matt Freeman from Larry Eddings, dated May 5, 2005 (attached). The second year of production was considered poor because of a dry winter. Production of strawberries grown on Camulos Ranch was compared to strawberries grown on the Oxnard Plain (see photo documentation and description). Irrigation water sampling during the second year showed chloride (Cl) was approximately 130 to 140 milligrams per liter (mg/L), and total dissolved solids (TDS) was in the range of 1,100 to 1,400 mg/L. The levels of Cl and TDS were “too high” for profitable strawberry production, and no more strawberries were grown after that by Pacific Gold Farms.” It was also clear to Mr. Eddings that “high EC accentuates Cl damage.” A “red flag” for Pacific Gold Farms is “100 mg/L Cl, and 1,100 mg/L TDS.” Mr. Eddings indicated that in his experience, “by the time you have visual symptoms in a plant, you’ve already lost yield - yield loss occurs before you see symptoms.” Both surface water and groundwater were used for strawberry production. No difference in water quality was observed between the two sources during this dry year.

Planting of strawberries takes place on or about October 1. Pre-irrigation takes place in advance of planting and is considered a “heavy” irrigation. Rain is mostly relied on through the winter months to keep the berries alive and growing; however, supplemental irrigation is common in dry years. Frost protection, if necessary, is accomplished through hand-move


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sprinklers. However, Mr. Freeman noted that “frost is not a concern for Camulos Ranch due to a micro-climate.” This was evident because there are no wind machines for orchards on Camulos Ranch relative to neighboring ranches. Lack of frost danger was attractive to Pacific Gold Farms for strawberry production. On average, it costs approximately $16,000/acre to produce an annual crop of strawberries.

Camulos Ranch has a 3-year contract with a different strawberry grower to plant berries beginning in October 2005, and anticipates increasing acreage in the remaining years. Some of these berries will be produced organically.

In general, strawberry production on Camulos Ranch, as described by Mr. Eddings, does not vary significantly from other areas visited with respect to irrigation method and cultural practices.

RDD/050550003 (CLR2818.DOC) A-53

Field Notes: Nursery Plant Production

Name and Location: Brokaw Nursery, Saticoy, California (eastern edge of Ventura)


Interviewee: Rob Brokaw



Overall Operation

The main crops Brokaw Nursery grows are avocado, citrus seedlings (lemons, oranges, mandarin oranges, and occasionally grapefruit), and kiwi vines. They have been in operation at this site for about 30 years, but will be soon forced to move because of encroaching development. In addition to finding a new location, one major concern they have is looming regulations regarding discharge of irrigation return flow.

General Comments Regarding Chloride

The nursery does not consider chloride to be a significant problem at this point, in that they are able to manage irrigation so that symptoms do not appear before normal leaf drop. They do not consider chloride content of their irrigation water to be as big an issue as it is in areas that use other water sources.

Chloride is not something they think about in their operation, and they do not consider it to be a particular problem. Rather, they look at overall salinity and manage this through irrigation. In the future, they envision that their liberal use of irrigation water will be curtailed and the salinity problem will become much more difficult to manage. Chloride will be a part of this management challenge but it will not be the central focus unless the chloride proportion increases. They expressed concern that if the new human populations upstream all install water softeners that they would be in a “very tough situation.”


They consider their well water to be of marginal quality for the crops they grow, and they report that other growers are surprised that they can succeed. The electrical conductivity (EC) of their well water is 1.7 to 1.8 decisiemens per meter (dS/m), with about 63 milligrams per liter (mg/L) chloride. The “poor” water results in the need to keep the root zone relatively wet and to use a high leaching fraction. After they add fertilizer to the flow, the EC ranges from approximately 2.4 to 2.5 dS/m. They add sulfuric acid to their water to lower the pH.

Table 1 is a well-water analysis the nursery provided.

FIELD NOTES: NURSERY PLANT PRODUCTION

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TABLE 1


Parameter Units Well Water With Fertigation

Calcium mg/L 139 139

Magnesium mg/L 40 45

Potassium mg/L 4 43

Sodium mg/L 98 113

Chloride mg/L 62.8 63.1

Total Alkalinity mg/L (assume as calcium

carbonate)

258 76.2

EC dS/m 1.72 2.39

pH Standard Units 7.8 6.4

Citrus

Citrus seedlings are grown in a greenhouse in tubes that are approximately 2 inches by 8 inches. Tubes are filled with a peat/perlite mixture, and “osmocote” slow-release fertilizer is also added. A network of pipes circulates warm water underneath the plants. Plants are irrigated with a hand sprinkler approximately 2 to 3 times per week, because they have found that no other type of sprinkler system will give them the uniformity they need. There are significant differences among citrus varieties in tolerance to sodium/chloride in sprinkler irrigation. With the water quality they have available and the citrus varieties they grow, they have not seen evidence of foliar toxicity.

Avocados

The major rootstock clones they use, in decreasing proportion, are Toro Canyon, Dusa (Merensky 2), and Duke 7. The scion variety is primarily Haas.

Greenhouse Procedures

Avocados are started from seeds in the greenhouse. Then two grafting procedures are performed, followed by a period where they are kept in the dark to produce the final product. One graft is to a South African type. Irrigation in the greenhouse is by hand sprinkler to obtain needed uniformity. Plants are irrigated about 2 to 3 times per week, depending on the weather. Plants are grown in plastic tubes that are approximately 2 inches by 8 inches, containing a very porous peat/perlite/redwood sawdust mixture. Seeds are planted in October, and the propagation process continues through the winter.


RDD/050550003 (CLR2818.DOC) A-55

50 Percent Sun

Plants are gradually hardened as they transition from the greenhouse to full sun. Plants are placed in an area where screens are used to obtain about 50 percent of normal sunlight. Irrigation is by hand sprinkler to obtain needed uniformity, and is applied about 2 to 3 times per week.

Full Sun

Seedlings are placed in black, plastic tubes or sleeves approximately 24 inches tall and 5 inches in diameter, open on the bottom to allow leaching. The seedlings are removed from the greenhouse media and are planted in the soil in the sleeves. The sleeves are placed on a layer of sand to prevent roots from becoming too securely anchored to the soil below the sleeves, because plants need to be moved occasionally during the production period and when they are sold. Growers (the nursery’s customers) are found along the California coast as far north as Monterey, and as far south as the Mexican border.

Seedlings are placed in full sun in March through April, and are grown for a year. The product is sold the following March. The entire process from seed to final sale of avocado seedling takes about 16 to 18 months.

The sleeves are filled with a soil mixture that they consider “dense,” which favors survival of the seedlings after they are planted in the producer’s field. The mixture consists of a mixture of redwood sawdust, mushroom compost, sand, and topsoil. Mushroom compost consists primarily of horse manure that has been used to produce mushrooms. Using a 100 percent sand media would produce plants of the desired size more quickly, but plants would do poorly after leaving the nursery and planting in the field. The salts contained in the mushroom compost are a concern, but they feel that it is an important soil amendment for their operation.

Irrigation is by drip, with one dripper per sleeve. Uniformity of avocado seedlings is an important attribute, and they work hard to achieve this. They have seen that flow decreases slightly along each run, and have considered feeding the flow from both ends to improve uniformity.

They generally irrigate during the day, in part because, inevitably, things break at night when nobody is available. Irrigation scheduling is a judgement (“an art”), and is not based on the California Irrigation Management Information System or other predictive tools. They apply approximately 1 gallon per irrigation per pot in four “pulses,” which consists of the following: an initial wetting, waiting an hour, a first irrigation pulse, waiting an hour, a second irrigation pulse, waiting an hour, then application of a final leaching pulse. They feel that pulsing the water achieves better leaching of salts. They estimate that they apply approximately 30 to 40 percent additional water to leach excess salts. Fertigation is applied during the two irrigation pulses. Drainage (irrigation return flow) is collected in a ditch that runs along the ends of the rows.

Other Crops

They have tried to grow an exotic Chinese fruit called lychee (Litchi chinensis), but the quality of their well water will not allow it.


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Recommendations from Soil and Plant Laboratory

Mr. Brokaw provided some recent reports and recommendations from Bill Darlington at the Soil and Plant Laboratory:

Boron and sodium continue to be present at relatively high levels.

All nurseries will need to curtail nutrient and water runoff in the near future.

Soluble salts of influent water are moderately high.

A number of nurseries use a water collection and reuse system. Depending on water quality, the water may be used to irrigate perimeter plantings, a subset of salt-tolerant plants, or may be filtered, blended with fresh water, fortified with nutrients, and reapplied in the nursery.

Watershed Considerations

Nearly all water used for irrigation in the watershed is from groundwater, as the river is not a reliable supply, especially in the summer when water is needed most. Frank Brommenschenkle, a Santa Paula-based consultant, is known as an expert in water supply issues in the area.

They believe that increases in irrigation water salinity would be more of a limitation to citrus than avocado in the watershed, because of the rootstocks that are used. If the quality of their well water decreases, they note that the discharge of their drainage or return flow will also be of lower quality (higher salinity), which will be increasingly problematic as regulations on discharge become more strict.

Avocados in the watershed are first established with drip irrigation for the first 6 to 14 months, and are then maintained using mini sprinklers. Fertigation is standard, and mulching with yard waste and compost is increasingly common.

Avocado rootstocks are either salt resistant or phytophthora resistant, but no varieties are known that are resistant to both. Phytophthora is generally the major hazard, but they can envision that being replaced by salinity concerns.

RDD/050550003 (CLR2818.DOC) A-57


Name and Location: Norman’s Nursery, Valley Crest Nursery, Moon Mountain Tree Farms, and LaVerne Nursery, Southern California

Communication Type: Site visits

Interviewee: Not applicable

Observer: Jim Jordahl/CH2M HILL


General Observations of Other Nurseries in Watershed

The following general observations were made of other nurseries in the Santa Clara River watershed.

Norman’s Nursery (northwest of Fillmore, Sycamore Road)

This nursery appeared to consist predominantly of small container stock, using fixed sprinkler irrigation.

Norman’s Nursery (east of Fillmore on Highway 126, north and south sides of road)

This nursery is a very large operation that appears to be focused on larger plants (trees), growing them in wooden boxes with drip (spaghetti tube or spitter) irrigation. A large section of trees was missing (30 to 40 acres?), which were apparently washed away in floods. In some area, some smaller material is placed between the larger boxed trees, with no obvious means of irrigation, suggesting these are hand-watered.

Valley Crest Nursery (west of Fillmore on Highway 126, south side of road)

This nursery is a very large operation that appears to be focused on larger plants (trees), growing them in wooden boxes with drip (spaghetti tube or spitter) irrigation.

Moon Mountain Tree Farms (just east of Piru)

This farm appeared to consist predominantly of larger, boxed material, irrigated with spaghetti tube or spitter-type drip irrigation. Palms and a number of other species were noted.

LaVerne Nursery (northwest corner of Piru)

This nursery appeared to consist predominantly of small container material with spitter-type drip irrigation. This was the only operation I saw that used drip irrigation for relatively small, containerized material. It is located on the side of a hill, just off the floor of the valley.

RDD/050550003 (CLR2818.DOC) A-59


Name and Location: Green Landscape Nursery, Saugus, California


Interviewee: Richard Green



(Mr. Green was very busy with retail operations when I stopped, and had very limited opportunity to talk. He asked me to leave a list of questions, which I did, and said he could fax back a response when he had more time.)

Overall Operation

Green Landscape Nursery is the largest nursery in Santa Clarita, with approximately 15 acres. They have a retail outlet and nursery facilities in Newhall and Saugus. They grow and sell a wide range of landscape and ornamental plants.


The nursery obtains water from both Santa Clarita Water Company and Newhall County Water District.

Retail Store

They manually sprinkler irrigate all of the plants at the retail store every day. They maintain a wide range of plants, including some of the following:

Shade structure – camellia, ferns, equisetum, Japanese maple, and many others

Outdoor small containers – pansies, iceplant, cactus, aloe vera, calla lilly, nandina, nerium oleander, star jasmine, tea rose, prunus spp., fan palm, mugho pine, juniper, and many others

Outdoor large containers (wedge-shaped wooden boxes, trees 10 to 15 feet or more in height) – white birch, camphor, magnolia, olive tree, flowering pear, southern live oak, sycamore, modesto ash, brazilian pepper, coast live oak, crape myrtle, coast redwood, sweet gum, palm, and a number of others


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Nursery Operations

Most plants in their nursery operations are drip irrigated, generally in the evenings. They grow different species at each location based on differences in water quality. The Newhall Nursery has significantly harder water than the Saugus Nursery.

Other Notes

Mr. Green requested a copy of our literature review report, and I agreed to give him a copy.

RDD/050550003 (CLR2818.DOC) A-61


Name and Location: Otto & Sons Nursery, Fillmore, California


Interviewee: Scott Klittich



Overall Operation

The production and sale of roses represents approximately 75 percent of their operation, and the remainder is the production and sale a variety of herbaceous and woody ornamental plants. They sell directly to retail stores rather than for landscaping, and quality is extremely important.


Table 1 is the well-water analysis they provided.

TABLE 1


Parameter Units Value

Calcium mg/L 125

Magnesium mg/L 51

Potassium mg/L 5

Sodium mg/L 92

Chloride mg/L 48

Total Alkalinity mg/L (assume as calcium carbonate)

200

Electrical Conductivity decisiemens per meter 1,360

pH Standard Units 7.7

mg/L = milligrams per liter

The laboratory recommended periodic application of urea-sulfuric acid (N-pHURIC) to remove 80 percent of the alkalinity to prevent plugging of the emitters. They feel that the major concern is the level of calcium, which results in unsightly white deposits on plant leaves if acid injection is not used; calcium forms a precipitate with an excessive acid, e.g., oxalic acid, and forms calcium oxalate.


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Water Treatment/Fertigation

They inject a mixture of ammonium nitrate (20 percent nitrogen), 2-0-8 for potassium, and N-pHURIC for irrigation of all of their plants. Fertigation/acidification is injected every 10 gallons of flow rather than continuously. Klittich believes that the N-pHURIC treatment is the key management tool that allows them to grow salt-sensitive plants with the water quality they have available.

Roses

They apply approximately 0.25 inch every night with fixed sprinklers for a number of reasons. It removes dust and reduces problems with mites and powdery mildew. Smaller potted material is irrigated by hand during the day, and the taller tea roses are irrigated with drip irrigation (spitter) tubes that operate at night. The spitter tubes run for 10 minutes per set. Hand-watered plants are irrigated once per day during the day. They have not seen evidence of salt injury.

Greenhouse Operations

They grow sensitive plants including azaleas, camellias, and gardenias in greenhouses. The irrigation system was originally laid out so that irrigation water supplied to the greenhouses was not treated, and they had problems with burning of leaf edges. They have not had problems with leaf burn since they began treating the flow with N-pHURIC, reducing the pH.

Other Nursery/Ornamental Plants

They grow a wide range of plants for retail outlets, including weeping pussy willow, flowering pear, bird of paradise, bougainvillea, euonymous, ferns, hibiscus, liquidambar, magnolia, palms, melalueca, pittosporum, prunus spp., sequoia, viburnum, wisteria tree, various fruit trees, and many other types of plants. The bird of paradise is noted for salt sensitivity, but they have not seen any problems. They regularly test alternative species on a small scale to determine how they will perform at the nursery.

Nearly all the plants they grow receive the 0.25 inch of nighttime overhead irrigation to eliminate dust. Some smaller potted material is irrigated with automated mechanical sprinklers. Larger potted or boxed plants are irrigated with the drip irrigation (spitters). Automated irrigation systems (spitters and sprinklers) are operated at night.

They occasionally try alternate plants, growing them on a small scale to see how they perform before growing them on a larger scale.


RDD/050550003 (CLR2818.DOC) A-63

General Comments on Watershed

The following are general notes about the watershed:

LaVerne Nursery operations at Piru primarily grow grafted ornamentals and citrus.

Valley Crest operations at Fillmore focus on the larger boxed trees, and Kittich believes the smallest product they grow is in 15-gallon containers. They had a lot of damage from the recent rains and floods.

Norman’s Nursery is a very large operation, with a number of facilities across California, including those near Fillmore. The company is firmly run by an ~80-year-old man, fully engaged in company operations. They also have had a lot of damage from the recent rains and floods. Staff at Fillmore consist entirely of laborers – there are no management staff around to talk with.

Mejias Nursery at Fillmore had major damage from the recent rains and floods, losing about one-third of their plants.

According to Kittich, from approximately Piru upstream, the climate is not favorable for citrus, avocados, and many nursery crops, because it is too hot in the summer and too cold in the winter. He noted that LaVerne’s operations at Piru were up on the side of a hill, and even the slight increase in elevation over the valley floor makes growing the products they do more feasible. Therefore, he does not think that these crops will be grown in the reaches of interest.

RDD/050550003 (CLR2818.DOC) A-65


Name and Location: Valley Crest Tree Company – Nursery Division South, Fillmore, California


Interviewee: Tim O’Neill



Conversation Details

Tim O’Neill provided the following information about nursery plant production in Fillmore, California:

Operations –

300 acres; about 240 acres are in production.

No propagating at the nursery; they buy seedlings, grow them, and ship them out.

Grow tree species only (they a have a complete wholesale catalogue with all tree species listed); at least 200 species.

Irrigation method – Microirrigation; drip or micro-sprinklers (spray stakes).

Irrigation management – 10-minute maintenance water block; once a week leach with about 120 percent leaching fraction.

Water source – three wells; the one closest to the river (about 1,000 feet away) is 60 feet deep.

Water quality – 7.2 to 7.4 pH; not sure of chloride and total dissolved solids (data are available).

Water is sampled every week.

Two injectors add fertilizer and N-furic acid (to prevent bicarbonates from clogging irrigation system).

Some boron problems.

Soil/growth medium –

They mix their own soil; they stopped using native soil because there was too much root rot fungus.


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Soil consists of sand, shavings (spruce, redwood, and cedar boxes they use for growing trees – for aeration, aggregation, and other, and also to reuse boxes), and preplant fertilizer (complements fertigation).

Soils are sampled monthly.

Pesticide use – Only on as-needed basis. Scouting indicates which trees need pesticide applications. Trees are mixed up by species, so pests do not spread to all the trees of one species. When the trees are shipped out, they have to be “commercially clean,” otherwise, they will violate the agricultural code.

Species salt sensitivity – This is not an issue here. O’Neill was not aware of species that they purposely did not grow because of salt sensitivity. Of the species they do grow, sequoias (coast redwoods) are the most salt sensitive.

Comments

Sespe River (directly upstream) is the biggest tributary to the Santa Clara River. (In our discussions with Darrell Nelson, this indicates that the Santa Clara River water downstream is likely not very salty, because of this tributary and Piru Creek. Water increases in total dissolved solids farther up the valley.) (Junction of Sespe Creek with Santa Clara River is at southeast corner of property.

O’Neill or someone else from the nursery has tried to attend all the Total Maximum Daily Load (TMDL) meetings, but often they are not notified in time. O’Neill submitted comments to the TMDL process about practicalities of certain practices.

O’Niell has had some contact with Julie Newman/Coop Extension; but, generally, Valley Crest is not on contact list and is not getting information

RDD/050550003 (CLR2818.DOC) A-67


Name and Location: University of California Cooperative Extension Horticulture, Ventura County, California


Interviewee: Julie Newman

Interviewers: Jim Jordahl/CH2M HILL


Briefly discussed nursery industry practice in Santa Clara River watershed. Irrigation practices and soil mixtures used in container nursery production are “all over the map,” and cannot be simply characterized. George Gutman (Bordiers) is a great source of information.

Flower growers are also an important part of this industry, and should be considered. This would include cut flowers grown in greenhouses, field-grown flowers, and hydroponic flower production in greenhouses. Fred VanWingerden (sp?) of Liberty Floral (805-985-7002) is very well connected and knowledgeable. (CH2M HILL was unsuccessful in contacting this person for an interview.)

RDD/050550003 (CLR2818.DOC) A-69


Name and Location: Green Landscape Nursery, Saugus, California

Communication Type: Telephone conversation (follow-up to January 20, 2005, site visit)

Interviewee: Richard Green



General Comments

The nursery only uses organic fertilizers, and they have found that this really helps winter survival. They mix organic fertilizers with the soil blend, then apply additional organic fertilizer every 4 months on the surface of the containers.

Green just received the copy of the literature review report that we sent him, as he requested.

Any evidence of salt or mineral damage on plant foliage is unacceptable because he cannot sell plants with any evidence of damage.

Saugus, California, Nursery Operations

The nursery grows ornamental tree stock in containers ranging from 15-gallon plastic up to 60-inch wooden boxes. The water source for this facility is the Santa Clarita Water Company, and the water quality there is more appropriate for salt-sensitive and mineral-sensitive (hardness) species. The Santa Clarita Water Company blends about 50 percent northern import water with groundwater.

Irrigation is about 50 percent by drip irrigation and 50 percent by manual watering. For the largest boxed trees, it requires hours of drip irrigation operation to provide enough water, so hand watering is preferred.

Irrigation is generally applied about every other day during the dry season, approximately May through October, but is adjusted for rain events during this period. During the winter, irrigation is applied sporadically, as needed, depending on climatic conditions. They would like to achieve some leaching of salts during the summer months, but most leaching occurs with the aid of winter rains. Evergreen species do not leach as well, because the plant foliage tends to shed the winter rains.

The trees they grow have very diverse water requirements. Water-intensive species grown at Saugus include flowering plums, flowering pears, sycamore, white alder, and coastal redwoods. The large, leafy trees generally do better with the water quality they have at Saugus, so are grown there rather than at Newhall.


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Soils used in the containers are a blend that they buy locally. They vary the blend depending on the needs of the various species. The blend is composed of a sandy loam soil, horse manure, and pine wood shavings. They add a mixture of gypsum and sulfur to the soil for species sensitive to alkaline soils.

No fertigation or water treatment such as acidification is used.

They have done experiments with reverse osmosis water on a limited basis, and have seen noticeable improvements in plants. They do not have the capacity to do this on a continuing or large scale.

One of Green’s major concerns regarding the use of recycled water on container trees is the buildup of nitrogen in the soil. Boron in the water is also a concern.

Newhall, California, Nursery Operations

Water supply is all well water, providing a harder, higher salinity water. The relative impact of salinity, boron, and hardness varies with the plant.

They grow less-sensitive species at this facility, such as palms and other drought-tolerant trees. In general, drought tolerance and salt tolerance have been correlated. Important species at this facility include crape myrtle, bottletree, fruit trees, Australian willows, magnolias, oaks, Palo Verde, and others.

Irrigation is almost entirely by drip and is applied daily during the dry season and as needed during the winter. Most of the annual leaching fraction applied is a result of the winter rainfall.

No fertigation or water treatment such as acidification is used.

The soil mix is similar to that used at the Saugus operation, but they only use a “light” mix, with more wood shavings and lighter soils. They add a pelletized gypsum product containing sulfur and iron at this site.

Accumulation of excessive levels of soil boron as a result of irrigation is a problem at this site.

Appendix B Literature Evaluation Tables

Avocados

5 Study Applicability 21 Study Quality 2 Total Score 28

This source is a critical review of the City of Escondido Avocado Pilot Project Final Report, published by Montgomery Watson and the University of California Cooperative Extension in 1997.

Scope - This source discussed all aspects of the reviewed study except for fruit quality.

Applicability - The study was conducted in Southern California on a typical site with a typical water scenario.

Quality - Questionable analysis, interpretations of data, and conclusions include the following:

1) "The yield reductions that were observed in the Beacon Hill Ranch experiment can be attributed to salinity effects alone, without invoking specific ion toxicity of chloride." First, this statement is based on Shalhevet's conclusion that salinity causes a certain rate of yield reduction; but it is unclear how Shalhevet knows that salinity, not chloride (Cl) toxicity, was indeed the cause of the yield reduction in his experiments? Secondly, this statement is not consistent with Amrhein's statement that "It is also difficult to separate salinity effects from the toxic effects of chloride because waters with high salinity are often high in chloride." Amrhein then proposed that Shalhevet's conclusions might not be applicable to avocado production in California, because avocados are being grown successfully at high salinity without the reduction in yield. The author's conclusion on the subject of salinity related to this project is unclear.

2) The author argues that summer average root-zone soil extract Cl concentrations were frequently very close (in certain treatments) to the 5-milliequivalents per liter (meq/L [178 milligrams per liter (mg/L)]) threshold (in irrigation water) recommended by Ayers and Westcot (1989) for leaf tip burn caused by Cl toxicity; and, thus, the high percentage of leaf tip burn in these treatments might have been partly caused by additional factors. However, the Ayers and Westcot "threshold" he references is a recommended guideline, must be considered with the leaching fraction, and is not considered a threshold.

3) Because multiple stresses on the trees during the course of the study made it difficult to identify one single factor that could account for the yield decline, this evaluator concluded that the results from this study should not be used to set irrigation water quality standards for Cl. Multiple stresses that contribute to yield impacts of certain factors are characteristic of field studies and define the purpose of why field studies are conducted. No field study lacks the multiple stresses that the author refers to; the design and implementation of a field study determine its relative quality and importance, rather than the naturally occurring obstacles that are beyond the experimenter’s control.

All other critical reviews of interpretations in the study, such as the effects of soil pH, boron, and nitrogen seem reasonable and are well referenced.

Review - Los Angeles County Sanitation District (LACSD) requested the document but did not review it.

Review PublicationsDocument Type

Study Scope

1.) Amrhein 1999

Tuesday, September 27, 2005 Page 1 of 64

Avocados


Scope - Preliminary results of yield impacts were discussed.

Applicability - This source is highly applicable to the project because of the location and nature of the experiment.

Quality - The study description and results were incomplete for this multi-year study.

Experimental StudiesDocument Type

Study Scope

2.) Arpaia et al. 1996


Scope - Cl leaf injury and sodium (Na) leaf injury were discussed.

Applicability - A different variety of avocado than is currently in use was studied.

Quality - Unclear conclusions include the following:

The author concluded that accumulation of Cl was associated with tip burn; however, it is unclear what is meant by "association," statistical or otherwise. The author speculated that the salt concentrations used in the treatments were too low to cause osmotic injury, saying that "The concentration of salts added to the nutrient solutions in this experiment were so low that it would be difficult to attribute the observed injury to the osmotic factor," but the basis for this statement is unclear. The treatments this statement referred to ranged in Cl concentration from 408 to 1,704 parts per million (ppm).


Study Scope

3.) Ayers 1950


Scope - This source presented general information about water quality, including salinity and potentially toxic ions.

Applicability - This source presented data for Cl thresholds adapted from Maas (1984), which are not site specific.

Quality - The source underwent a high level of review. Thresholds included associated assumptions regarding soil extract salinity (assumed at 1.5 times that of irrigation water) and leaching fraction.


Study Scope

103.) Ayers and Westcot 1985


Scope - No treatments were imposed.

Applicability - Measurements were made of Fuerte avocado leaves exhibiting various degrees of leaf burn.

Quality - Evaluations were subjective; no statistics were used.


Study Scope

4.) Ayers et al. (a) 1951


Avocados


Scope - This source presented Cl versus nitrate salts and discussed specific ion toxic effect versus osmotic effect.

Applicability - A high leaching fraction was used (40 percent). Rates were from 71 to 568 ppm Cl. Mexican rootstock used but not Hass variety.

Quality - The source was well documented. No control was used. The authors' claim that experimental design isolated salinity effects is questionable; more accurately, it isolated Na and Na salt effects. The analysis included qualitative evaluation and regression. Evaluator comments on the authors' conclusions include the following:

1) "Toxic symptoms appear only when chloride is the main anion" (as opposed to nitrate). "This suggests that within the range of salinity and chloride concentrations used in our studies, the toxic symptoms are not due to osmotic effects, but rather to chloride-specific toxicity." The assumption is made that experimental design isolated Cl effects from osmotic effects, but this may or may not be possible because the solutions were made of salts. More clarification on the assumption that all salts cause similar imbalances in osmotic potential needs to be discussed. The authors' assumption is that if the injury were caused by the osmotic effect, then the osmotic effect would have occurred with the other salts too.

2) High-Cl water can be used to irrigate avocados without deleterious effects if nitrate is continuously supplied at a concentration equal to half that of the Cl. Other studies have found that doing this long term can be detrimental. This conclusion is the result of the short study duration.


Study Scope

6.) Bar et al. 1997


Scope - This source discussed seed propagation of avocados.

Applicability - This project has low applicability to the Upper SCR; it discussed avocados in Israel.

Quality - This source was a review that provided no references.


Study Scope

7.) Ben-Ya'acov 1976


Scope - Several phases of one experiment were presented.

Applicability - This source had little applicability to the project because studies were conducted in Israel, and no information was given on irrigation practices, soil types, and other site conditions. The Hass variety was not used.

Quality - Yields differed significantly among and within populations. Little difference in productivity was observed when irrigation water had a Cl content of 100 ppm or less, but production in Mexican rootstocks declined to about half that of the West Indian rootstocks when Cl concentration was 300 ppm. This is not the final report for this study. Little description was given in this source about experimental procedures.


Study Scope

8.) Ben-Ya'acov et al. 1992


Avocados


Scope - This source discussed avocado production factors that impact yield.

Applicability - Southern California was the area of discussion.

Quality - The conclusions were supported by a combination of referenced studies, personal communication with growers, and the author's personal experience.

General - "The major climatic factor affecting avocado yields in this state appears to be temperature during the blooming period. A difference of even a degree or two can have a major effect on fruit set (Hodgeson and Cameron, 1936)." Questions yet to be answered include the following:

-Why is this important factor not reported in most avocado field studies? -Is this dated information, or does it still apply? -Are newer varieties that have been developed since the 1936 study less sensitive to temperature during bloom?


Study Scope

9.) Bergh 1967


Scope - This source evaluated growth parameters on their ability to indicate salt sensitivity, but did not relate the parameters back to yield.

Applicability - West Indian rootstocks were used.

Quality - The analysis included qualitative ranking, analysis of variance (ANOVA), and correlation. Interpretations of data were solid. A main conclusion was presented: salt stress could result in growth stimulation or growth inhibition of shoots, so biomass production per branch is suggested as a better indicator of salt sensitivity. The study was well documented.


Study Scope

10.) Bernstein et al. 2001


Scope - The source focused on salinity, sodium chloride (NaCl) in particular, and not Cl.

Applicability - West Indian rootstock was used.

Quality - This is a well-documented study. The author's main conclusion was that rootstock that was considered to be relatively salt tolerant, judging from leaf damage, was actually very sensitive to salinity in terms of root growth. The avocado is unique in that salinity affects root growth more than shoot growth. In other plants, the opposite is true. Therefore, root growth is suggested to be the indicator of salt sensitivity rather than shoot growth parameters.

General - The discussion of unique avocado root morphology, which may increase sensitivity to soil salinity and affect nutrient uptake, is worth noting.


Study Scope



Avocados


Scope - No Cl treatments were imposed; irrigation rates and nitrogen rates were imposed; only soil samples were analyzed; and no information about Cl or salinity tolerance or effects in avocados was provided.

Applicability - The source gave some useful information about the extent to which Cl and salts concentrate in soils that are irrigated with water that is relatively low in salts.

Quality - The full description of site conditions, study background, and objectives were not given in this source. No information was given about design, randomization, or how the irrigation and fertilizer were applied. Linear regressions were used to analyze data. No information was given about soil physical properties, even though this study was primarily about soil parameters. The authors concluded that frequent irrigation produced higher Cl levels and lower nitrate levels.


Study Scope

12.) Bingham and Richards 1958


Scope - This source included many aspects of Cl injury, including a discussion of mechanisms.

Applicability - A sand-culture study was performed on applicable varieties.

Quality - The source was well documented and presented useful and relevant data. Main problems with the interpretations and conclusions from this study include the following:

1) How did the authors choose 15 meq/L (533 mg/L) soil-water Cl concentration as the threshold for a Cl hazard? The data table that showed the effects and significant differences of treatments on leaf Cl, leaf injury, trunk diameter, relative transpiration, fruit harvest, and fruit oil did not support any one treatment as being the one where injury starts to take place. Also, fruit harvest among treatments, which is arguably the most important and telling growth parameter, was not analyzed with ANOVA to determine significant differences among treatments. Toxic symptoms began to appear at 10 meq/L (355 mg/L), so it is unclear why the authors did not choose that level as the Cl hazard. In fact, yield results were considerably less at 5 meq/L (178 mg/L). There was no explanation of why they chose the particular value that they did, leading readers to believe that their choice was subjective.

2) The treatments were isosmotic (all treatments had the same solute concentration). The symptoms very obviously increased with increasing Cl in the treatment solutions. Therefore, the statement, "Rather than being a specific effect, the effect appears to be a special case of osmotic injury," is only partly true. If the effect were clearly increased by increasing Cl, then even if it is a special case of osmotic effect, it is still specific to Cl.

3) There was no discussion of type of salts and variability in treatments because of different cations and addition of nitrate.

4) The authors made the assumption that tip burn was the first symptom of Cl injury to occur. (More recent research indicates that root injury might occur first.)


Study Scope

11.) Bingham et al. 1968


Avocados


Scope

Applicability

Quality


Study Scope

107.) Branson and Gustafson 1972


Scope - The study did not focus on Cl; it focused on water stress and leaf-water potential.

Applicability - The source is useful for determining osmotic potential of avocado leaves.

Quality - This study was well documented.


Study Scope

14.) Chartzoulakis et al. 2002


Scope - The experiment imposed Cl treatments, analyzed leaf content and leaf injury, and made no measurement of other growth parameters to determine salt tolerance.

Applicability - The study was conducted in Texas.

Quality - The control treatment irrigation water, which was used to water the plants before the salinization was begun, produced tip burn. The study trees were only irrigated for 3 months, which is probably not long enough to truly determine salt tolerance.


Study Scope

15.) Cooper 1951


Scope - The experiment imposed no Cl treatments, and leaves with tip burn were analyzed for mineral content.

Applicability - West Indian and Mexican rootstocks were used in this Texas study.

Quality - Qualitative statements were made about leaf content of constituents (i.e., higher or lower), but no formal analysis was performed.


Study Scope

17.) Cooper and Gorton 1950


Avocados


Scope - Tip burn was observed, leaf Cl and Na were measured, and soil electrical conductivity (EC) was measured.

Applicability - Mexican and West Indian rootstocks were used in this Texas study.

Quality - The thresholds established in this study referred to the maximum salinity at which no injury occurs. The authors pointed out (from personal experience it is assumed, because this was not tested) that avocado trees can survive and grow at salinities beyond the threshold, even though leaf tip burn occurs. They suggested that the long-term presence of salt injury would eventually cause the tree to stop producing; however, they did not specify how long "long term" is. Although the study was based on EC levels, the authors referred to tip burn as the injury symptom, which has been documented elsewhere as a Cl symptom specifically. Therefore, the meaning of these results is unclear in relation to other literature.

General comment - The conclusions seem to be based more on interpretation of results extrapolated to management practices from personal experience, and not on the results of the experiment.


Study Scope

16.) Cooper et al. 1952


Scope - No growth measurements were taken. The study focused on root and leaf accumulation of Cl and Na only. The mechanism of injury was discussed. Growth parameters were measured. Leaf tissue analysis was performed.

Applicability - Hass variety was grafted onto various rootstocks.

Quality - Replications and controls were identified. Randomization was not explained. The length of the study was not given. Significant differences were identified versus nonsignificant differences, but no explanation was given about the statistical method used to determine those differences. This source was proceedings from a symposium and not published. The experiment was ongoing at the time that the document was written. No final documentation was found.


Study Scope

18.) Crowley et al. 1999


Avocados


Scope - Growth measurements were taken, ion determinations made, and flowering response noted. NaCl treatments were applied.

Applicability - Fuerte variety on various rootstocks was studied in sand culture.

Quality - No information was given on the number of replications or how they were implemented. No information was given on randomization. The author concluded that because the roots of plants were exposed to salinity in the soil solution approximately three times as high as that of the irrigation water, irrigation water containing 2 to 4 millimoles (mM) NaCl would lead to salinity problems, particularly if scions (shoots) were grafted to salt-intolerant rootstocks. This conclusion was stated in terms of known salinities of river water used to irrigate avocados. However, the study results did not indicate any such range. The study results indicated that at 5-mM NaCl (= 292.5 mg/L NaCl or 178 mg/L Cl), injury and growth-inhibition symptoms begin to occur. The range given by the author was speculation and was in reference to the river water (that has these salinities) that was of concern. Because this treatment was the lowest noncontrol treatment, we can interpret that injury symptoms might occur at lower salinities, but the treatments did not allow the experiment to determine that.


Study Scope

19.) Downton 1978


Scope - NaCl treatments were applied, and leaf tissue analysis was performed.

Applicability - Foliar application of irrigation water was used.

Quality - This was a qualitative analysis only (of numerical data).


Study Scope

20.) Ehlig and Bernstein 1959


Scope - Cl content of injured leaves was discussed.

Applicability - The authors conceded that their results were not that useful or applicable in California because the rootstock they found to be more tolerant of Cl was not used in California for other reasons.

Quality - There was no mention of a control in this source, probably because the study was a mensurative field study. Replication and randomization were mentioned, although the experimental design was difficult to decipher. It would have been helpful to have a summary of the types of trees in each of the orchards, because the results were given by orchard. It appears as if the results were from one sampling event only. The objectives of this study are unclear. Prior to this study, several others had already shown the difference in Cl tolerance among different races of rootstock. The study served to confirm what had already been found in at least seven other studies, as pointed out by the authors in the discussion. The authors offered no explanation for why they received the results they did, or the mechanisms governing Cl uptake and tolerance.


Study Scope

21.) Embleton et al. 1962


Avocados


Scope - Cl hazard level in irrigation water for avocados was discussed.

Applicability - The study was conducted in the local area.

Quality - Study quality criteria are not very applicable here because no studies were referenced. The document was based on personal experience.


Study Scope

68.) Faber 2004


Scope - Irrigation rate treatments were discussed.

Applicability - The source is highly applicable to the project at a regional level.

Quality Implementation - Implementation of irrigation treatments was inconsistent; the number of blocks was reduced because of external factors affecting the experiment.

Analysis - The analysis was incomplete and mostly qualitative. Cumulative yields were shown but not analyzed. No data on soil salinity was shown or discussed. Regression was used instead of ANOVA because treatments that were intended to be discrete actually formed a continuum. This field study was 4 years.


Study Scope

22.) Faber et al. 1995


Scope - This source reviewed a research program in Israel.

Applicability - This source has low applicability to the project in terms of location, soils, and climate.

Quality - Recommended thresholds of Cl concentration in irrigation water for avocado production in Israel are 120 to 150 mg/L for Mexican rootstock. The source did not cite specific studies.


Study Scope

25.) Gazit and Kadman 1976


Scope - Osmotic adjustment and a study on mature avocado embryos was conducted.

Applicability - Mexican rootstocks were studied.

Quality - This study was well documented.


Study Scope

26.) Gonzalez-Rosas et al. 2003


Avocados


Scope - Thresholds on leaf burn were presented, but not growth or yield.

Applicability - Mexican race avocados were not included.

Quality - This is an extension publication. The threshold tables are unclear, because the table notes do not match up with the values given. The threshold tables represented maximum Cl concentrations that trees can tolerate without developing leaf burn.


Study Scope

27.) Grattan and Oster 2002


Scope - This source presents a thorough review of salinity and ion toxicity mechanisms.

Applicability - The information was not specific to avocados.

Quality - The conclusions were referenced; however, they assume knowledge of water potentials. For example, the significant statement, "There is some direct evidence that high internal chloride and/or sodium concentrations reduce growth. This comes from two approaches which separate effects of ion excess from water deficits: (a) Growth or yield of some species is reduced at such low external Cl concentrations (5 to 10 mM) that adverse effects of low osmotic potential are implausible, e.g., avocado, soybean and grapevines," is not explained.


Study Scope

28.) Greenway and Munns 1980


Avocados


Scope - No Cl treatments were imposed. The study measured effects of different irrigation water quality and soils. A qualitative assessment of leaf burn was presented. The entire research program, which included several studies, ran from 1956 to 1962. The studies included the following: irrigation timing and method (with respect to leaching); tensiometer study; correlated irrigation water, soil, and leaf Cl content, and irrigation timing.

Applicability - The field trial was conducted by extension staff.

Quality - It is not clear if and where the study was published. No information was given on avocado tree age or varieties, similarities and differences among the nine orchards that were used in the research program (except for soil types), or irrigation design or methods. Randomization and replication were identified, but a control was not identified. Little information was given on experimental design and methodology. The source lacked a thorough exploration of data. The author presented some interesting data that were inconsistent with expected outcomes and the conclusions of the study, but did not discuss them. In particular, the following inconsistencies were not discussed:

1) In data Table 1, some sites showed lower Cl levels in leaves than other sites with higher Cl levels in the irrigation water. (Compare Fallbrook #2 to Rincon Springs, or Loucadia to Carlsbad.)

2) In data Table 1, the degree of tip burn did not always increase with increasing leaf Cl content. (Compare Loucadia with Vista.) Tip burn was also not necessarily consistent with irrigation water Cl levels. (Compare same orchards.)


Study Scope

30.) Gustafson 1962


Scope - This source summarized basic avocado irrigation principles, scheduling, salinity problems, factors for determining water needs, and irrigation systems. Avocados cannot stand drought, but excessive moisture restricts root activity and favors root diseases. The discussion was general.

Applicability - The source is applicable to the project at a regional level.

Quality - The statement, "The higher the chloride content of irrigation water, the more frequent the irrigation should be and the more water should be used. If the amount of chlorides exceeds 100 ppm, extreme care should be taken in how water is used," was not referenced, but a statement from personal experience. Not all studies confirm the conclusion about irrigation frequency stated here.


Study Scope

29.) Gustafson 1976


Avocados


Scope - This study compared drip irrigation with the sprinkler method. The source reported results from the first year of the study.

Applicability - Hass variety was used.

Quality - Randomization was not identified. No mention was made of the presence or absence of tip burn. Fertilizer was applied weekly through the drip system, and the sprinkled trees were fertilized by hand twice a month. There was no discussion of how this might have affected soil salinity differently (other studies have shown that fertilization affects soil salinity). The evaluator assumes that the trees were on Mexican rootstock because "thresholds" for Mexican rootstock were referenced later in the source, but the author did not identify the rootstock of the trees. The author assumed there was an "established threshold" for Cl and salt levels on Mexican rootstock; this was not referenced, so the evaluator assumes that the author is referring to Bingham et al., 1968, considering what the values were (5 meq/L [178 mg/L] for Cl). The conclusion, "Results of the monitoring program during the first year indicate that control of soil salinity in the root zone was adequate for both sprinkler and drip irrigated trees," is based on this assumption. Also, the statement, "Under drip irrigated trees, some accumulation of soluble salts beyond the recommended limits occurred, but only in the 0 to 6 inch depth, for which the values were 3 millimhos (mmhos) total soluble salts and 8 meq/L Cl," is not lucid. This Cl level is reasonably high (284 ppm), and most avocado roots are in the shallow part of the soil (0 to 12 inches, with the majority in 0 to 6 inches). Therefore, it is unclear why this was not a concern.

The study would have been more useful if Cl injury symptoms were assessed, considering that soil Cl levels were a major part of the study. The final report for this study could not be located.


Study Scope

31.) Gustafson et al. 1973


Scope - Background information of the Upper SCR was provided.


Quality - The criteria presented were not applicable. No study was involved. Personal experience was the basis for the information.


Study Scope

37.) Haas 1928


Scope - Only fruit quality was discussed.


Quality - Little information on study implementation and methods was provided.


Study Scope

35.) Haas 1936


Avocados


Scope - Na and calcium interactions were presented with no focus on Cl.

Applicability - Mexicola seedlings were used. The source is applicable to the project at a regional level.

Quality - The source focused on results, not methodology. Little or no information was given on various aspects of experimental design and implementation.


Study Scope

32.) Haas (a) 1950


Scope - Cl leaf burn and root-growth inhibition were discussed. The source contrasted calcium and NaCl salts.

Applicability - Mexican rootstock was used.

Quality - Some of the methodology was not described, such as the treatment application method, timing, and any leaching.


Study Scope

33.) Haas (b) 1950


Scope - Leaf tissue from an existing orchard was analyzed. No treatments were imposed.

Applicability - No site description was given for the orchard. Regional applicability is assumed.

Quality - The sources lacked a site description and thorough description of experimental methods.


Study Scope

34.) Haas (c) 1950


Scope - Magnesium and calcium Cl interactions with ammonia nitrogen were presented.


Quality - Proper evaluation of this source is difficult because it was written in a manner that was difficult to follow. The focus was on the results, but little information was given on experimental design and methodology.


Study Scope

38.) Haas and Brusca 1955


Avocados


Scope - NaCl treatments, leaf analysis, soil analysis, and mechanism of Cl tolerance were presented.

Applicability - Mexican and West Indian rootstocks in Israel were studied.

Quality - Although the author's analysis did not explore the correlation between Cl injury ratings and leaf Cl content, there does not seem to be a strong relationship between these two factors (by a simple regression analysis). Yet, the author stated, "In general, a close correlation was found between the Cl content in the leaves and the leaf scorch, so that for practical purposes scorches of this type can be identified with Cl accumulation in the scorched tissues." There was no presentation of data to prove this. Also, other studies (such as Gustafson, 1962) presented data that would prove otherwise.


Study Scope

40.) Kadman 1963


Scope - Na injury (using NaCl) was discussed.

Applicability - Mexican and West Indian rootstocks in Israel were studied.

Quality - Little information was given about the two experiments conducted in this research program. No data were presented. The brief discussion focused on qualitative statements about study results. Over 500 seedlings were used, so there was adequate replication. No information was given about experimental or treatment design, or controls that did not receive the 830-ppm NaCl treatment.


Study Scope

39.) Kadman 1968


Scope - Several experiments were presented with a very wide scope. The mechanism of salinity resistance, mechanism of Cl uptake and transportation, and mulching effects on Cl levels were discussed.

Applicability - This study in Israel used Mexican rootstocks in some cases.

Quality - These brief descriptions excluded some important information about how the experiments were implemented, such as what rates were used, how treatments were applied, what kind of soil was used, and how the treatment was designed.


Study Scope

41.) Kadman and Ben-Ya'acov 1969


Avocados


Scope - Optimal water dose was discussed.

Applicability - The Hass variety on West Indian rootstocks was used in Israel.

Quality - The authors did not identify the soil type, which is an important factor in leaching effects. The authors stated in the results section that the irrigation rate was varied between treatments, but not the frequency. Evaluator comments about interpretations and conclusions of the study follow:

The statement, "Estimating the total Cl input (250 mg/L in irrigation water + fertilizer) up to the time of the mid-summer soil analysis in 1985 to 1986, and comparing it to the increase of its concentration in the 0-90 cm soil layer during the same interval, indicated that the increase of soil Cl accounted for 108 percent, 56 percent, and 34 percent of Cl input in the 70%, 100% and 130% irrigation treatment, respectively," is not necessarily meaningful because 1) we know the irrigation Cl input was 200 to 250 mg/L, but the authors do not say what the estimate of fertilizer Cl input was; and 2) we do not know what type of soil the study was conducted on.

In addition, Kurtz et al., stated that Steinhardt et al., (1984) (a reference we do not have because it is in Hebrew) claims that a 30 percent leaching factor nullifies the input of 300 mg/L Cl. An 86 percent increase in water input was not sufficient (in this study) to completely eliminate Cl and EC buildup in the soil during mid-summer. This was a comparison of two different things. A 30 percent leaching factor (usually) refers to 30 percent more water applied than the water requirement of the crop, or 100 percent crop ET. Here, Kurtz et al., referred to an 86 percent increase in water applied as the ratio of the lowest treatment to the highest treatment (70 percent/130 percent). This 86 percent cannot truly be called a leaching fraction, because the base water applied was only 70 percent of ET and not 100 percent. Therefore, Kurtz et al., in fact, used a 30 percent leaching fraction with their 130 percent treatment, not an 86 percent leaching fraction. Secondly, it is unknown if these two studies are comparable in their soils.


Study Scope

42.) Kurtz et al. 1992


Scope - This source summarized the findings of studies on water-nutrient relationships in avocados.

Applicability - This source presented a review of studies from Texas, California, Israel, and Martinique.

Quality - Brief descriptions of studies and interpretations of study results were provided.


Study Scope

43.) Lahav and Aycicegi-Lowengart 2003


Avocados


Scope - Two trials were performed. The first was on water irrigation rates, and the second was on irrigation rates and Cl treatments.

Applicability - Hass variety on Mexican rootstock was used in Israel.

Quality - For the first experiment, the source did not fully explain what 60, 80, 100, and 120 percent of the standard amount of irrigation usually applied was. The major flaw in this experiment was the lack of control, because nitrogen was increased as water was increased. Therefore, the conclusions that 1) the irrigation regime significantly increased fruit yield and trunk circumference; and 2) fruit size also increased as more water was applied, cannot be attributed to water treatment alone. We do not know if the water, the nitrogen, or both caused these impacts.

For the second experiment it is also unclear how and when the variable Cl treatment was adjusted, or for what purpose. The authors stated that an increase in "salinity" from 90 to 380 mg/L Cl reduced Hass yield by 25 percent; however, it is unclear how the Cl was applied (i.e., as what type of salt). Without knowing this, it is impossible to tell if it really was the effect of Cl or a combined effect of Cl and another ion making up the salt. The duration of this research is unclear.


Study Scope

44.) Lahav et al. 1992


Scope - This source presented the same data as Maas, 1984.

Applicability - No conditions were associated with thresholds (such as management); sources of data were not necessarily applicable to Southern California; and some site-specific data from Texas were used for avocado thresholds.

Quality - Cl thresholds were estimated from calculated Cl levels in soil extract based on soil extract EC. The chapter referenced sources of data.


Study Scope

104.) Maas 1990


Scope - Soil solution salinity results of an irrigation frequency and system position trial were discussed.

Applicability - At this site, the winter rainfall leaches the entire root zone of soluble salts. This does not always happen in Southern California. West Indian rootstocks were used, but in this source, only the soil solution results were given. The authors implied that the roots have an effect on how much the salts/Cl are concentrated in the soil. It is unclear, but this may be dependent on the race of rootstock. Irrigation water equals 210 ppm Cl.

Quality - Experimental design was well documented. Analysis, interpretations, and conclusions were reasonable, although not as thoroughly explored as possible (only soil solution results were provided).


Study Scope

49.) Meiri et al. 1999


Avocados


Scope - This source discussed salt tolerance. Cl was measured but not isolated from Na.

Applicability - The three most commercially important avocado rootstocks currently used in California were studied, including the Hass variety. The source is applicable to the project at a regional level. The authors stated that because Na and Cl were applied simultaneously in their study, it was difficult to determine the relative effect of either ion on physiological responses to salinity. Rates were high (ranging from approximately trace to 1,600 mg/L Cl), so it was not possible to determine threshold. Even at the first noncontrol treatment level (approximately 450 mg/L), Cl was already at damaging levels in leaves (0.4 percent).

Quality - The study was well documented. Interpretation of the data was reasonable and thorough; although, no conclusions regarding affects on roots were provided. Root growth was not measured. Given that leaf necrosis of the most sensitive variety was below 5 percent at the 3.0-decisiemens per meter (dS/m) treatment level (approximately 450 mg/L Cl), leaf necrosis might not be telling the complete reason for plant injury; root measurements would be needed.


Study Scope

50.) Mickelbart and Arpaia 2002


Avocados


Scope - Yield impact and irrigation requirement were discussed.

Applicability - This long-term field study is highly applicable to the project at a regional level.

Quality - The main problems the evaluator identified with the paper include the following: The literature review was incomplete, hindering the ability of the authors to make informed interpretations and conclusions of data analysis. The source lacked references; presented an incomplete data analysis, causing uncertainty regarding results of the study; and lacked clarity in presenting the analysis of yield data, causing uncertainty of study results. These problems are describe in detail below.

-Study implementation problems were acknowledged, but not addressed or taken into consideration when conclusions were drawn about yield and other results. The literature search was not "extensive" as described in the introduction. Many significant articles were excluded, leading to questionable interpretation of some data. In general, the source was lacking references. For example, p. 6-4 under "Soil pH": "Avocado is thought to do best in a soil pH range of 5.5 to 7.0." Thought by whom? Also p. 6-7 under "Chloride": "Excessive chloride in the tree appears to reduce fruit set in the spring of the following year." There is no reference. The evaluator has not seen a study that proves this.

-"Leaf Samples" section under "Grove Study Description": Unclear. It looks like some text was modified and then repeated. Is the leaf sampling protocol standardized? It was not referenced. Other literature has indicated that leaf sampling is a precise procedure. It is not clear here whether any specific methodology was followed for any specific reason.

-"Project Results and Trends" section, paragraph under "Chloride": Unclear. Was it a summer or annual average?

-The authors did not offer an explanation for why the soil extract EC was higher in the 140 percent ET treatment than the other treatments (except for the 100 percent ET treatment), yet the yields were higher.

-"Leaf Data Trends" on p. 6-10: The authors stated that it is unclear why watering with reclaimed water did not increase nitrogen levels in leaves. A more extensive literature search would have revealed that the likely reason for this is that there was not enough nitrogen to override the Cl uptake. An incomplete literature search leads to questionable interpretation of data analysis.

-p. 6-10: The authors stated that the best reclaimed water treatment in terms of the lowest Cl accumulation in the leaves was the 50/50 blend treatment, showing Cl levels significantly lower than the pure reclaimed water treatments. The yield results, however, were not correspondingly higher in this treatment. Although the authors did not address this inconsistency, it is an important finding that Cl leaf accumulation might not be correlated to yield.

-The authors seem to be of mixed mind when it comes to which yield data to use. First they stated that it is unreasonable to look at yield in individual years, because the yield varied so much. So, the 4-year yield summaries were presented. However, if the yields varied so much from year to year, we can assume that the coefficient of variation for these data would be very high. Is taking an average of these yields reasonable? Or is averaging the percent decline reasonable? Then they stated that the yield from the last 2 years would provide a better analysis of yield because the trees had recovered from thinning and underirrigation. How tree recovery was determined was not explained. Also, if the yields were so variable, why would taking fewer years of data provide a better analysis? Thirdly, the yield data for the last 2 years seems more variable than taking


Study Scope

51.) Montgomery Watson 1997


Avocados

the years before that into consideration. The first year (1993) of yield data was very high compared to other years, but the countywide data indicated that this was true across the county, and it was just a good year for avocado production.

-ANOVA on 2 years of data does not seem like a very robust test. These appear to be the only statistics that were done on the data, except for those mentioned below.

-Paragraph 3 on p. 6-15: This does not make sense. Two comparisons were done between two treatments in each comparison. The authors stated that the 140 percent ET treatment had a higher yield compared to the other two treatments, but the 140 percent treatment was only compared to one other treatment (the 100 percent ET treatment). What is the second treatment they are referring to?

-p. 6-18: The authors stated that fruit from rows 5 through 8 were not included in the storage test because some of these trees had root rot. Were fruit from these trees included in the yield data? This is not addressed in the yield section, but it is likely that root rot would affect yield.

-The authors did not address the potential interaction between salinity and root rot and Cl.

-p. 6-18: If internal fruit quality is related to chilling injury, why was it rated? What does chilling injury have to do with the study? Is not this a post-harvest issue? Chilling injury, it seems, would introduce another variable to fruit quality that was not directly a result of the treatments, or is it? This connection is unclear.

-p. 6-19: Side and stem rot do not appear to have the same results with regard to treatments. Why is this not discussed? At what point is the difference between treatments significant?

-"Summary" section on p. 6-19: The authors stated that "during the course of the experiment, Excondido's reclaimed water reduced the yield of commercial avocados by 42%." This is not entirely true because, first, it refers to the entire study (the evaluator thinks), but the authors stated that the last 2 years of the study provided better data for yield analysis. Again, this is really unclear throughout the source. Secondly, there are so many factors that affect yield, it is quite a large leap to conclude that a treatment, especially in a field trial, was the sole cause of an increase yield decrease, especially when there were so many acknowledged problems with the field study implementation.

-Paragraph 4 of Section 7 "Conclusions": Again, it is unclear if the authors were discussing the statistical difference for the yield results from the entire study or from the last 2 years.

-The authors performed statistical analysis on the yield results - the most variable factor and the one influenced by so many things - but there was no statistical analysis on other parameters in the study. Perhaps yield was considered the most important dependent variable; however, other analyses would have provided a means to correlate yield with other factors. Helpful correlations could have included the following:

Tip burn with yieldYield with soil salinityYield with soil ClTip burn with soil salinityTip burn with soil Cl

-Data in this study were presented, but not really analyzed. The ANOVA test that was performed was poorly presented. It is unclear if it was for the last 2 years of the study, or for the entire study. Results of the ANOVA were stated as a "better analysis"; however, that is not what is emphasized in the summary and conclusions, and executive study. Consistency in this regard would have made the paper more useful


Avocados


Scope - This source provided a review of results from Cl studies on avocados. It discussed salinity effect and specific ion toxicity.

Applicability - Regional studies (and others) were included.

Quality - The report was requested and reviewed by LACSD. Evaluator comments on the author's interpretations include the following:

-The author stated that "excessive salinity lowers the osmotic potential of the soil solution. This limits the ability of the plants to obtain sufficient water from the soil to produce maximum yields." This is a general statement that is not necessarily true at all levels of salinity (depending on what is meant by excessive). The author also stated that "Past studies also indicate that crop yields may be reduced by specific ion toxicity." There were no references to support this statement.

-The author stated (regarding the 180-mg/L guideline for avocados proposed by Bingham) that three field studies "did not provide information that indicates this guideline should be changed." This is somewhat ambiguous in that it is unclear by the wording whether the information provided was actually consistent or not.

-The author stated that between 60 and 80 percent of the yield reduction reported by Montgomery Watson (1997) and Shalhevet (1999) could be attributed to salinity and not a Cl-specific ion toxicity. This statement is questionable for the following reasons:

1) The yield reduction in Montgomery Watson (1997) was never clearly established in the study results. The authors provided confusing yield results from ANOVA that were based on the last 2 years of the study, yet their conclusions were based on yield results from all the years of the study. Furthermore, the yield results were highly variable from year to year, as is typical of avocados.

2) The yield reduction in the above study could have been caused by several other factors, including study implementation problems, underirrigation, mites, soil pH amendments, and other production factors that naturally come into play in a field trial, and were acknowledged in the study.

3) The above study did not include an objective to determine if growth effects and/or yield reduction were caused by ion-specific effects or osmotic/salinity effects, so the authors did not conduct sampling/testing to determine the physiological mechanism that caused the yield reduction. Furthermore, the authors did not provide any analysis of yield data comparing it to other effects (such as tip burn, soil Cl, or soil salinity) that would help determine what caused the reductions in yield.

4) Shalhevet developed a theory/formula to calculate percentage of yield reduction that could be accounted for by salinity. The applicability of this formula to California has been questioned by other authors (Amrhein, for example) because avocados are grown in the state under high-salinity conditions. It is questionable that this formula is applicable to all sites.

5) Because yield is influenced by so many factors, many of which are out of the control of the grower/researcher (such as temperature during bloom), the reduction in yield could be attributed to salinity; but the likelihood that this could be determined with certainty is low.

-The author stated that "the Bingham guideline of 180 mg/L is the only one that is based only on experimentally determined chloride effects on growth that are not confounded by the effects of applied water


Study Scope

53.) Oster 2002


Avocados

and salinity of the irrigation water." This statement is questionable for the following reasons:

1) Cl was applied as a salt in the Bingham study; therefore, the effects of salinity cannot be completely ignored.

2) Data from the Bingham study showed that significantly different effects from the Cl treatments began occurring at various treatments, depending on what parameter was being measured. It is therefore unclear why Bingham et al., chose the 180-mg/L guideline. This level of treatment is where leaf injury became definite; however, ranking of leaf injury symptoms were subjective, and there is little understanding (in this study and others) about how leaf injury is related to yield. The guideline is apparently not based on the yield results, because they were not statistically analyzed (although data on other growth parameters was statistically analyzed). The author clearly stated that his choice was a "judgment" of the data, and not based on any particular analysis of the data.

-In evaluating the Bingham study, the author stated there were no significant differences in yield between treatments. The author did not perform statistical analyses on the yield treatments; and looking at their range, it is likely that there were significant differences among any of the yield effects.

The main conclusion of the section discussing salinity was that new avocado research trials indicate that "salinity effects on avocado yields were larger than chloride effects." It is unclear what this means. Did growth respond more to salinity effects than to Cl effects, or did the salinity effects occur earlier than Cl effects, or did salinity mask other effects? The study objectives did not include differentiating between these effects. Also unclear is the explanation of how salinity was attributed to 60 to 80 percent of the yield reduction in these studies. Because applied water was varied, it is not clear how water effects were isolated from salinity effects.


Avocados


Scope - Yield impact, irrigation rates, and specific ion effect were discussed in this source.

Applicability - Regional studies were used.

Quality - This article was requested and edited by LACSD. The evaluator’s main comments regarding the interpretations and conclusions of the authors include the following:

-The Cl threshold given as a result of this study was estimated using several assumptions, comparison of studies that differed in many ways, and a production function that may be applicable on certain sites, but was shown to underestimate the yield impacts of salinity in this case. (Shalhevet, 1999, points out that a production function for the water requirement of avocados can be developed; however, the spread of data is large because of differences between years, sites, rootstocks, varieties, and cultural practices.)

-The theory behind the assumptions and calculations used in the study were not fully explained, and the article is difficult to understand and interpret.

These points are described in further detail below:

-"Corrected for rain, the salinity of the applied water averaged 0.7 dS/m and the chloride averaged 70 mg/L." This is an assumption that is not commonly used in the literature. Is it possible to correct for rain, because the effect of the rain on leaching out soil salts depends on when and how it comes?

-The authors assumed "steady state" conditions in the field. How did they know that "steady-state conditions" (not defined) existed in the field? This seems unlikely, and more appropriate for controlled environment experiments.

-The explanation of how the production function was used is vague, and multiple assumptions were necessary.

-Data for the 130 percent water treatment in 1997 were not used. The authors did not state why.

Evaluator comments regarding the Escondido 2 and Akko Istrael (Salinity/Chloride) section follow:

-Many assumptions were made and, as a consequence, the results from this study were strongly theoretical.

-It was not clearly explained why the study was designed using a 100 percent ET for the lowest three salinity treatments, and with 140 percent for the highest salinity treatment. This seems to distort the effects of the salinity variable, because leaching fraction can affect soil salinity.

Evaluator comments regarding the Santa Clara River TMDL section follow:

-The authors stated that the production function they used to estimate yield loss from salinity underestimated the yield loss in the latter two experiments, yet their conclusions in this part of the article did not seem to acknowledge that statement.

Evaluator comments regarding the Conclusion - Application section follow:

-The conclusion is unclear. It discussed salinity and Cl at the same time, when the authors claim to have


Study Scope

55.) Oster and Arpaia 2002


Avocados

separated out the effects of Cl earlier in the study.


Scope - This source summarized studies carried out at Brokaw nurseries.


Quality - Little information was given about experimental design, study implementation, and data analysis. The authors stated that the reason the results from the second experiment were not consistent with other experimental data was perhaps because the plants were harvested before the hot, drying conditions of the summer months. However, they did not address that the results from the second experiment (which differed from the first) might have been a result of the lower salinity/Cl levels used in the second experiment. Lack of information prevents this source from being more useful.


Study Scope

56.) Oster et al. 1988


Scope - Pruning, irrigation requirement, and tip-burn observations were described in this source.


Quality - LACSD requested this paper, but it was not externally reviewed. On page 1, the author stated that two methods of canopy management ("stumping" avocado trees down to 3 feet and regrowing them, and cutting 30- to 40-foot trees down to 15 to 20 feet) "have both resulted in greatly reduced incidences in leaf tip burn as the avocado trees are not having to move water up 30 to 40 feet into the trees." The theory behind this statement was not stated, and is seemingly counterintuitive. Cl moves with water; therefore, Cl would have less distance to travel to affect leaves. This theory was never explained. Data that proves these results were not given, nor was it written up anywhere in the literature. No data were presented. Personal experience was documented.


Study Scope

57.) Partida 2002


Scope - Salt tolerance, mineral uptake, Na, Cl, photosynthesis, and transpiration were discussed in this source.


Quality - Data were presented, but no statistical analysis was performed on experimental data. Some data on leaf-water potential were presented. The following statements by the author are unclear:

"Although Huntalas was sensitive to salts, very little Na was found in top leaves. Salt injury then was not due to Na accumulation of either in roots." The meaning of this statement is unclear.

"…Cl concentration was 25 times higher than Na at the same salt treatment. Similar results were obtained in the fruit experiment for Na accumulation." The “fruit experiment” was not discussed.


Study Scope

58.) Patel et al. 1976


Avocados


Scope - The source included an evaluation of leaf scorch and mineral composition. Only one NaCl treatment was imposed. Fuerte-Mexican seedlings were used.

Applicability - Site conditions were different from the project (e.g., climate). This was a field study.

Quality-Materials and methods - This section provided a good description of site, soils, and climate, although they were different from the Upper SCR. Irrigations were also very infrequent and not typical of the Upper SCR. It is unclear how the two groups of trees with different levels of symptoms were selected. Were they like this naturally, or were treatments imposed to develop this difference in symptoms?

-Results and discussion - There was seasonal variation in irrigation water quality. The authors stated that soil EC increased at the end of irrigation season in all depths. The evaluator is not sure how this conclusion was made because the Materials and Methods section stated that soil sampling was only performed at the end of the irrigation season. The authors stated that "leaf P is lower in trees with symptoms of salt stress and even lower in scorched leaves of these trees." However, the symptoms of salt stress were not defined, nor was the ranking system of evaluating the degree of stress. They also stated that "sodium concentration was similar in all leaves and below the limit considered as toxic for avocado." However, they did not state what that limit is.

-Observations (qualitative and based on personal experience for the most part) - Leaf Cl was high throughout the sampling period. In trees that did not show salinity stress (again, not defined), leaf Cl was similar for trees showing tip burn and those not showing tip burn. However, in trees that showed salinity stress, Cl was higher in tip-burned leaves than in leaves that were not scorched.


Study Scope

59.) Salazar-Garcia and Cortes-Flores 1988


Scope - Soil salinity, leaf-water potential, and stomatal conductance were discussed in this source.

Applicability - Mexican rootstock was used in a greenhouse setting in Mexico (no information was provided about climate).

Quality - Replication and randomization were identified, but no control. A very brief description of the study was provided. Only leaf-water potential and stomatal conductance were measured. Levels of Cl used in treatments were very high (233, 700, and 1,400 ppm), indicating that levels this high were needed to observe effects in leaf-water potential. Brief results were presented, but no discussion of results or conclusions was provided. The duration of the study was not given.


Study Scope

60.) Salazar-Garcia and Larqué-Saavedra 1985


Avocados


Scope - This source provided a general review on irrigating with saline water.

Applicability - General concepts were presented, and little specific information on avocados was given. Much of the information presented in this source was from other countries and is therefore not directly applicable to the Upper SCR in terms of soils and climate (or, possibly, in cultural practices). In addition, much of the information was derived from experiments on citrus because there was little data available on how avocados respond to different cultural practices (including irrigation methods) and their relationship to water and salinity.

Quality - This source provided a thorough review with cited studies. The author presented some results of studies on the response of avocado trees to salinity, but drew no conclusions.


Study Scope

62.) Shalhevet 1994


Scope - Salinity and water management were discussed.

Applicability - California irrigation practices were considered. The locations of reviewed studies were varied.

Quality - The source provided a summary of several cited studies. Data were presented, but few conclusions were drawn.


Study Scope

105.) Shalhevet 1999


Scope - Cl and the general effects on avocado growth were presented.


Quality - This source documented the author's personal experience. The threshold of 100 ppm for avocados was not described in detail - in irrigation water versus soil extract or for injury versus yield.


Study Scope

63.) Thomas 1932


Scope - Cl and the general effects on avocados were presented.


Quality - This source documented personal experience. It recommended a specific threshold for irrigation water on avocados.


Study Scope

64.) Trask 1960


Avocados


Scope - Effects of NaCl on Cl accumulation and injury were discussed.

Applicability - The Ettinger variety on Mexican rootstock was used in a greenhouse. The study was conducted in Israel.

Quality - There was no apparent control in the experiment. In the discussion, the authors noted that other researchers have documented that yield is reduced without leaf burn. The study was well documented.


Study Scope

67.) Wiesman 1995


Strawberries


Scope - This source was a series of guideline tables that suggested tolerance thresholds of some crops, including strawberries, to Cl in irrigation water. Sources and explanations of these threshold values were not provided.


Study Scope

272.) ANZECC 1992


Scope - This study focused on strawberry yield response to salt accumulation in soils under furrow and sprinkler irrigation. The study scope was limited to salts, in general, and it did not differentiate between Cl and other salts. The study provided a general conclusion that irrigation water containing more than 100 ppm of Na plus Cl can result in salt accumulation, but it did not specify the Na or Cl levels in study irrigation water or irrigation management practices.

Quality - Little information was provided about the study implementation or design.


Study Scope

270.) Brown and Voth 1955


Scope - This source summarized the California strawberry industry and contained background information on strawberry production.

Applicability - Some of this information included cultural practices that were applicable to coastal strawberry production in California.


Study Scope

271.) California Strawberry Commission 2004


Applicability - This source is an extension publication that provided general production information for strawberry producers in Iowa and surrounding areas. It contained some general production and site selection guidelines that were useful for background information, but for the most part was not applicable to the Upper SCR.


Study Scope

273.) Domato et al. 2000


Strawberries


Scope - This source described an aquaculture study that measured Cl accumulation in plants that were given salinized irrigation treatments with specific concentrations of Na and/or Cl. The primary purpose was to compare Cl uptake from sprinkler versus root irrigation applications.

Quality - The source provided information about formulation of treatments and frequency of application. The study evaluated paired treatments replicated in a randomized design and included a control treatment.

-Cl concentrations in plant tissue were compared with qualitative assessments of plant injury in the form of leaf burn. Other potential effects, such as stunting or yield impact, were not evaluated. Statistical methods were not mentioned. Conclusions were well defined relative to the purpose, but were not useful in determining thresholds for Cl injury because negative effects that could occur before leaf necrosis were not monitored. The study duration was approximately 110 days.


Study Scope

274.) Ehlig 1961


Scope - This source described a two-part investigation - a sand-culture study and a field study. Because these studies included different implementation methods and purposes, they were evaluated separately as "Part A" and Part B", respectively. This evaluation refers to the sand-culture study.

Objective - The stated objective was to study osmotic and specific ion effects on the growth of strawberries.

Applicability - The source provided information about formulation of treatments and frequency of application, but the method of application was not specified. Differential treatments were not applied until approximately 6 weeks after the start of the study, giving plants an establishment period with lower salt concentrations. Lassen and Shasta varieties were evaluated.

Quality - Each treatment was replicated and included a control, but the source did not specify if treatments were randomized or not. No statistical methods were mentioned. The study duration was approximately 5 months.

Conclusions of this study stated that the osmotic pressure of the nutrient solution was the predominant factor in determining growth. This was because growth of one variety was as poor under sodium sulfate (Na2SO4) salinization as under Cl-based treatments. Although Na2SO4 effects took much longer to appear than CaCl2 and NaCl effects (2 to 2.5 months versus approximately 10 days), visible plant injury was observed in all treatments on both varieties (including control), indicating influences on injury outside of added treatments.

Plant tissue Cl content was related to marginal burn, with increased Cl levels correlating with increased margin burn. Marginal burn was very slight or absent when Cl contents did not exceed 35 meq/100 grams plant dry weight.


Study Scope

275.) Ehlig and Bernstein, Part A 1958


Strawberries


Scope - This source documents the second part of the investigation described in the Ehlig and Bernstein, Part A, source. This evaluation refers to the field-plot portion. Specific effects of Cl were not the focus of this study, and no efforts were made to isolate Cl from other salts.

This portion aimed to determine effects of increased salinity on strawberry yield and quality. Information was provided on formulation of irrigation treatments. Equal parts NaCl and calcium chloride (CaCl2) were used to salinize treatments. Salinization was initiated after an establishment period with no added salt (approximately 6 weeks).

Applicability - Irrigation scheduling and management were generalized, and the method was not stated.

Quality - Conclusions were drawn based on combined salinity only. No statistical methods were mentioned. This study was replicated in a Latin square design and included a control treatment.


Study Scope

281.) Ehlig and Bernstein, Part B 1958


Scope - This source focused on strawberry response to salinity when grown in coconut fiber and expanded clay substrates. Salinity treatments were achieved by addition of NaCl. This source provided information regarding solution formulation and irrigation management. Plant growth, fruit yield, and fruit quality were monitored.

-Results showed that the effects of salinity were more sharply evident at lower treatment levels, indicating that a control, if not more treatments with lower increments of salinity, might have provided more insight about a salinity threshold. No efforts were made to distinguish Cl effects from combined salinity effects, so the results and conclusion of this study were not useful for Cl threshold determination.

Applicability - Plants were established with lower salinity levels for the first week.

Quality - The study was replicated in a randomized complete block design; however, no control treatment (no added NaCl) was applied. Statistical analysis of variance was conducted for each presented parameter.


Study Scope

276.) Giuffrida et al. 2001


Scope - This source provided general information and guidance related to irrigation management for salinity control in strawberry production. It provided guidelines for determining leaching fractions and approximating yield losses based on soil or irrigation water EC. It also provided a brief and general discussion of specific ion toxicities and a suggestion that Cl concentration in soil saturation extract not exceed 175 to 260 mg/L, although it did not cite a source or supporting information for this recommendation.


Study Scope

277.) Grattan 1991


Strawberries


Scope - This source discussed field evaluations conducted in the Santa Maria Valley for purposes of determining real applied water values, irrigation system uniformities, ET rates, and salinity patterns around driplines.

-This field study monitored actual strawberry production farms within the constraints of real operations. The results provided good insight about actual operational conditions, including irrigation water application, drip irrigation uniformity, and leaching fractions.

-Some irrigation water salinity analyses were run, and results ranged from 1 to 2.36 dS/m. Cl was not specifically analyzed. This source did not evaluate crop responses to any of the parameters monitored and, thus, is useful for background operation information only. It did not provide any insight about responses of strawberries to chloride.


Study Scope

278.) Hansen and Bendixen 2004


Scope - This study examined effects of increased salinity on yield and fruit quality of several strawberry cultivars. Salinity treatments were achieved by addition of NaCl. This study did not distinguish Cl effects from salinity effects.

Applicability - The source provided information on solution preparation and irrigation method and management. The study used drip irrigation. Treatments were begun after an unspecified establishment period.

Quality - This study was replicated and arranged in a randomized complete block design. A 0.5-dS/m treatment was the control. Statistical analysis was performed.


Study Scope

279.) Kepenek and Koyuncu 2002


Scope - This study examined different Cl/sulfate ratios in nutrient solutions and the effect on strawberry Cl uptake and growth after cold conditioning.

Applicability - This study focused on examining management practices and varieties that are not applicable to the Upper SCR.

Quality - Composition of the nutrient solutions was provided, but other study implementation parameters were not clear, and irrigation management and methods were omitted.

-The study noted a significant positive relationship between supplied Cl and Cl uptake. The study also showed no significant difference in plant growth or fruit production; however, it cited high variability in plants, and the duration of treatment application and timing of monitoring were not defined.

-Treatments were replicated and randomized and some statistical analysis was performed; however, many details of study implementation and methods were not clearly defined.


Study Scope

280.) Lamberts et al. 1989


Strawberries


Scope - This source summarized the second year of a 2-year effort. Another interim study paper was summarized, but for evaluation purposes, the study was reviewed as a whole.

-This study examined the influence of bed mulch, irrigation rates, deficit irrigation, and overhead sprinkling on strawberry fruit bronzing.

-The primary reason this study was originally reviewed was to determine if Cl had potentially been monitored or cited as a factor in fruit bronzing. However, Cl concentrations were not monitored or mentioned in this study, and results did not link Cl to fruit bronzing.


Study Scope

282.) Larson et al. 2002


Scope - This source provided general information strawberry production that was more applicable to cold-region production. No information on Cl thresholds was included.


Study Scope

283.) Manitoba Agriculture, Food and Rural Initiatives 2001


Scope - This was a general source providing information on salinity management practices in strawberry production. The source discussed irrigation water quality, irrigation practices, drainage, and bed formation relative to salinity management.

A section of this source discussed specific ion effects of Na and Cl. The source indicated that calcium helps to offset concentrations of Na and Cl. Suggestions for maximum Cl levels were provided for soil solution (5 to 7 meq/L [178 to 249 mg/L]) and irrigation water (3 or 5 meq/L [107 to 178 mg/L]). However, neither the source nor supporting information of these suggestions was provided.

This source included a table of irrigation water quality restrictions that included Cl levels that would result in none, some, or severe restrictions for surface and sprinkler irrigation methods. This table was obtained from Ayers and Westcot Food and Agricultural Organization of the United Nations Irrigation and Drainage Paper 29.


Study Scope

284.) Schrader and Welch 1990


Scope - This source provided background information regarding strawberry production in California and some information about production regions of California. This source did not mention Cl or salinity effects on strawberry production.

Applicability - Strawberry varieties and cultural practices were the most applicable topics discussed.


Study Scope

285.) UC Fruit and Nut Research and Information Center 1999


Strawberries


Scope - This source provided general information about the effect of cultural practices on salinity in California strawberry production. The author cited some general irrigation parameters and results from a field station experiment examining different row arrangements and bed heights, but this source was not specifically written to present a study and does not provide any detailed study information.

Applicability - The irrigation method used in this case was surface, and total applied water depended on whether it was a summer or winter planting (5 acre-feet for summer plantings and 3.5 acre-feet for winter plantings). The salinity of this water was mentioned, but the Cl concentration was not.

The irrigation practices discussed in this source are not applicable to the Upper SCR, and specific Cl concentrations or Cl effects were not discussed.


Study Scope

286.) Voth and Bringhurst 1967


Scope - This source provided general guidance regarding preplant preparations for strawberry production. The source cautioned use of certain salt-containing soil amendments or fertilizers, but otherwise provided little information relative to salinity or Cl concerns. The source did not mention Cl specifically.


Study Scope

287.) Welch and Beutel 1987


Scope - This source provided general information on strawberry production. General recommendations for fertilization and soil conditions were provided. This source did not discuss Cl limitations of strawberries.

Applicability - The information provided was not specific to California.


Study Scope

288.) Wichmann 2004


Nursery Crops


This source is an extension leaflet designed to provide information on water quantity and quality considerations for container nurseries in North Carolina.

Scope-Growth stage - Young plants are more sensitive.

-Ion toxicity versus osmotic effect - The leaflet mentioned both effects briefly, describing them as potential effects. Osmotic effects were described in terms of preventing water uptake, leading to wilting, stunting, and burning of leaf margins. Cl-specific effects were described for certain species, including roses, azaleas, camellias, and rhododendrons.

Applicability-Location and climate - This is a North Carolina State publication.

-Irrigation method - The irrigation method was not clearly linked to the thresholds suggested and, therefore, conclusions, but stated that sprinkler irrigation of container stock was only a practical method, which is consistent with Upper Santa Clara River (SCR) nursery practice.

Quality-Conclusions - Cl thresholds were not linked to any research. Species were not clearly linked to an irrigation method.


Study Scope

311.) Bailey et al. 1999


Nursery Crops


This source is an extension-type bulletin. It provided an understanding of salinity-related concerns for homeowners and site managers, including tools to diagnose and manage salinity.

Scope-Specific ion versus osmotic - This source briefly mentioned the potential for specific ion toxicity; however, it did not discuss osmotic issues in detail.

Applicability-Location and climate - This document was general, targeted at western states, and not specific to California or the Upper SCR. It was justifiably applicable, but not critical to the study conclusions.

-Rootstock - This source mentioned numerous species that are relevant to the Upper SCR, including lantana, oleander, pittosporum, rose, and viburnum. The maximum soil ECe is suggested for major species, and limiting irrigation water electrical conductivity was suggested for two relevant species (rose and guava).

-Cultural practices - This source concentrated on landscape plantings and not nursery production, which limits its applicability.

-Irrigation management - This source concentrated on landscape plantings and not nursery production; therefore, it is not applicable.

-Routes of exposure - This source provided some maximum soil ECe values for common western shrubs. Because most nursery production of shrubs uses sprinkler irrigation, this criterion suggests limited applicability.

Quality-Conclusion - This source provided a range of sound diagnostic and management recommendations and some guidance on irrigation water quality thresholds. It did not discuss the differences between foliar- and soil-applied irrigation water.

-Review - We can reasonably assume that an ARS publication cannot be released without peer review.


Study Scope

320.) Bernstein 1964


Nursery Crops


This is a seminal paper. It is one of three most frequently cited sources to establish relative tolerance of nursery species.

Scope-Specific ion versus osmotic - Both osmotic tests (range of salinities with NaCl + CaCl2) and isosmotic tests (NaCl, CaCl2+NaCl, CaCl2, and Na2SO4 were all designed to decrease water potential by 2.2 bar) were conducted.

-Physiological mechanism - This source discussed a hypothesis on mechanism (effect of Na and Cl on stomatal closure), but contained no experimental tests to evaluate. It only provided anecdotal evidence based on observations of apparent drought-related burning of foliage of landscape plantings near the research facility, coupled with measurements of low Na and low Cl in the leaves.

Applicability-Location and climate - This research was conducted at Riverside, California.

-Irrigation method - Flood irrigation was discussed; thus, its applicability to nursery practice in the Upper SCR is limited.

-Soils - This source was specific to native soils and sand tanks and, therefore, is not similar to container soils in the Upper SCR.

-Rootstock - Numerous relevant species were included, and species differences were fundamental to the objectives and conclusions of the source.

-Cultural practices - This source did not provide detailed descriptions of cultural practices.

-Irrigation management - Weekly irrigation was conducted for Experiments 1 and 2; this was not well described for sand tanks and Experiment 3.

-Routes of exposure - This source discussed root uptake and, therefore, is relevant to large container production where drip irrigation is used.

-Rate of exposure - Stepwise salination was used on Experiments 1 and 2; therefore, this is not applicable for this project. Sand tanks and Experiment 3 were not explained.

Quality-Design - In this source, all experiments included control and replication; however, experimental design was not explained other than the randomization they achieved by reversing the planting pattern 180 degrees for each row.

-Analysis - This source only provided summary data; no statistical analysis was presented.

-Interpretation - This source provided detailed interpretations and explanations of the data; no statistical analysis was presented. The data on growth, visible effects, and Na and Cl uptake were not presented with sufficient clarity to allow a complete assessment of the validity of the interpretations. The isosmotic sand-tank experiment should have been separated and explored as a separate paper for at least a few example species.


Study Scope



Nursery Crops

-Conclusion - The conclusions in this source did not include the wide range of interpretations that were discussed therein. The conclusions were restricted to the relative tolerance among the species to salt in the root zone. Lack of a consistent correlation of Na and Cl uptake data with salt tolerance was consistent with their data. The conclusions were also compared and contrasted with other studies.

-Implementation - In this source, details on study implementation was variable. The evolution and implementation of Experiments 1 and 2 were fairly well described. However, leaching fractions used were not explained for Experiments 1, 2, and 3.

-Duration - In this source, the species were limited to shrubs and groundcovers, and experiment durations were 2 years, 2 years, and 5 years. The duration of Experiment 3 could not be determined from the source, although it appears to be less than 2 years. These durations seem reasonable for the species tested.

-Review - This source was published in a major journal, so thorough peer review can reasonably be assumed.

-General comments - Because of the inconsistencies in data relative to Cl versus osmotic effects presented in this source, confirming or disproving the conclusions is difficult. Growth data were not presented on isosmotic treatments. No data were provided to support the conclusion that growth with Na2SO4 is not superior to NaCl in the sand tanks. In this source, the authors emphasized that the data presented on Figure 1 (relative plant salt tolerance) represented general salt tolerance and not Cl tolerance, although Cl is the dominant anion in the salt solutions. This is contrary to the interpretation suggested by Maas (1990). The correlation between growth and ion uptake data was not explained well in this source, and, therefore, a second paper should be prepared to explain this correlation in detail.

-Soils experiments - Total Cl in low salt treatment was 1,000 mg/L NaCl = 611 mg/L Cl and 1,000 mg/L CaCl2 = 639 mg/L Cl; sum = 1,250 mg/L Cl. Therefore, even the low salt treatment was very high in Cl.

From the information presented, there was a wide range of responses to Cl among these plants, such as salt tolerance versus Cl uptake, Cl uptake versus leaf effects, and extent of burn before leaf loss.


Scope-Specific ion effect and osmotic effect - This source explicitly described potential effects and effects of Cl transported to leaves by roots and foliar-applied irrigation. This source did not explain which factor was most important.

Applicability-Location, climate, and soils - This is a New Jersey extension publication, resulting in relatively low rankings for these factors.

-Rootstock - This document discussed Cl effects on camellias, stone fruits, and roses, which are all relevant species to the Upper SCR, but are not a factor in the study conclusions.

-Routes of exposure - This document discussed soil- and foliar-applied irrigation effects, which are applicable, but are not a factor in the study conclusions.

Quality-Conclusion - The conclusion was rated relatively low (1), because no original references were provided for the Cl thresholds suggested. A table of values was taken from a California extension leaflet (Farnham), and also reviewed here. No discussion of differences in standards by species or irrigation method was provided.


Study Scope

306.) Cabrera 2003


Nursery Crops


This source provided a brief summary of the nursery industry in California. It referenced recent data from the California Agricultural Statistics Service.

Scope - Essentially no information on salt tolerance or Cl was provided; nevertheless, it provided helpful background on the nature and scope of the industry.

Applicability - This source was highly applicable to the project, because it included data for the Ventura and Los Angeles County nursery industry. However, the data were not specific to the Upper SCR.

Quality - It seems clear that Carman is the academic authority on this subject in California, and the data from the California Agricultural Statistics Service was based on real, county-level reports.


Study Scope

309.) Carman 2003


This source focused on listing relative salt tolerance of ornamental plants to total salt. It was a somewhat global review, although there appears to be a bias toward plants adapted to the north-central and northeastern United States and toward the impacts of salt applications to roadways and on adjacent ornamental plants.

Scope-Growth stage and yield impact - This was discussed only briefly.

-Specific ion effects - These were not mentioned.

-Osmotic effects - These appear to be assumed, but were not specifically discussed.

Applicability-Location and climate - The source of the data being summarized was not always clear, but it appears to be predominantly based on data from more northern and colder climates than the Upper SCR.

-Soils - Soils were discussed, but not in relation to salt-tolerance results.

-Rootstock - Mostly northern-climate, deciduous species were discussed, although there were a few that appear to overlap with those grown in the Upper SCR (e.g., roses, hibiscus, oleander, and pittosporum).

-Routes of exposure - The source briefly discussed salt spray and accumulated soil salt, but it was not clearly connected in the source to plant tolerance.

Quality-Review - This source was published in a trade journal, so the level of peer review is uncertain.


Study Scope

302.) Carpenter 1970


Nursery Crops


The author is a local industry expert with Soil and Plant Laboratory in Orange, which is a lab used by many nurseries in Southern California.

Applicability - The author works every day with nurseries across the area, including those in the Upper SCR, to manage soil and water quality issues. Therefore, his opinions and experience have to be considered highly applicable for all criteria.

Quality - There was no study design or implementation to evaluate. In general, the author’s major conclusion relative to the Upper SCR was that the 3-meq/L (107 mg/L) upper limit on Cl for sprinkler irrigation suggested by Ayers and Westcot (1985) is a useful standard for the industry. His conclusion was not tied to any specific trials in the area.


Study Scope

315.) Darlington 2004


Scope-Specific ion versus osmotic - This leaflet described both as potential effects. Osmotic effects were described in terms of water availability. An entire section of the leaflet was devoted to specific ion toxicity issues, including Cl.

Applicability-Location, climate, and soils - This is a California publication; thus, it is generally applicable to the Upper SCR.

-Irrigation method - The leaflet provided specific recommendations for soil (surface applied) versus sprinkler irrigation, both of which are relevant to the Upper SCR and explicitly part of the study conclusions (threshold recommendations).

-Rootstock - Extensive tables were provided on relative salt tolerance of ornamental species relevant to California, although no information was provided that linked these to Cl thresholds given in the leaflet.

-Irrigation management - Recommendations were given on managing salinity, especially leaching fraction, but information was not connected to recommendations on Cl threshold values.

-Routes of exposure - (see irrigation method.)

Quality-Conclusions - The text report was unusually thorough and detailed for an extension pamphlet, but did not provide any basis or citations for its recommendations regarding Cl limits; therefore, it was given a relatively low score. The summary table was similar in format to Table 1 in Ayers and Westcot (1985), but had some slight differences. Extensive data on relative salt tolerance for ornamental species were provided, but not in terms of Cl.


Study Scope

307.) Farnham et al. 1993


Nursery Crops


This study is third in a series of United States Salinity Laboratory (USSL) studies on ornamental species. The source was similar to previous sources, but additional species were added to their database.

Scope-Specific ion versus osmotic - The author measured Cl and Na in leaves, and made some comments on relative uptake; but the study of osmotic versus specific ion uptake was not within the scope.

Applicability-Location and climate - The studies were done at Riverside, California, and, therefore, are at least somewhat relevant to the Southern California area. However, location was not a factor in study conclusions.

-Irrigation method - Flood irrigation is not typical of Upper SCR nursery production.

-Soils - Pachappa sandy loam was used in test plots, which is not typical of Upper SCR nursery production in containers where artificial soils are used.

-Rootstock - The species used are relevant to the Upper SCR and crucial to the study conclusions.

-Cultural practices - Little data were provided about cultural practices.

-Irrigation management - The study provided irrigation weekly during the summer and “as needed” during the winter.

-Routes of exposure - Roots were exposed to salinity and, therefore, representative of large container production. However, this was not a factor in study conclusions.

-Rate of exposure - Treatments were implemented using stepwise salination and, therefore, not applicable to Upper SCR conditions.

Quality-Design - The design included four replications and nonsaline control, but the randomization was not clear.

-Analysis - No statistical analysis was provided.

-Interpretation - No statistical analysis was provided. It is unclear how the author was able to construct Table 2 from the three levels of salinity used. The soil salinity treatments were 1.5, 6.0, and 9.8 dS/m, yet the orchid tree was assigned a maximum root-zone salinity of 4 to 5 dS/m. Although this is probably a reasonable interpretation from the available data, the associated uncertainty with the values presented is not clear.

-Conclusion - Conclusions were mainly limited to the relative salt tolerance of the species examined, which was supported by experimental results. However, the strength and the clarity of the conclusions were not as strong and well developed as the previous two papers in this series.

-Implementation - The study provided a reasonable record of implementation, with only limited questions from the evaluator regarding timing, approach, and milestones. Some example questions relate to the following: frequency of winter watering, leaching fractions used, soil moisture content, soil fertility, variability of soil salinity among plots with the same salinity treatment, and variability of plant growth and foliar effects.


Study Scope

323.) Francois 1982


Nursery Crops

-Duration - Three growing seasons were used, which is reasonable, and beyond the duration of most comparable studies.



Nursery Crops


This is one of three USSL papers on this topic. The paper and method closely paralleled Bernstein et al. (1972), except Francois and Clark did not include an isosmotic sand-tank study.

Scope-Specific ion versus osmotic - The study conducted tissue testing of Cl and Na, but no other exploration of osmotic versus ion toxicity issues other than comparisons of burned leaf tissue concentrations with general literature values for Cl and Na injury were made.

Applicability-Location and climate - The study was conducted at Riverside, California; therefore, it is relevant to the Upper SCR, but it is not expressed as critical to the study conclusions.

-Irrigation method - Flood irrigation was used; which is not typically used in the Upper SCR.

-Soils - Pachappa sandy loam field plots were used; therefore, it is not generally applicable to container production.

-Rootstock - A range of species were included in the study, including a number of species important to the nursery industry in the Upper SCR.

-Cultural practices - Limited data were provided, but practices included winter pruning.

-Irrigation management - Weekly irrigation was provided in the summer, and as needed in the winter. The study was not applicable to nursery production with typical daily to every-other-day watering.

-Routes of exposure - The roots were exposed to the saline solutions and, therefore, applicable to large container production.

-Rate of exposure - Salt solutions were applied in a stepwise manner; therefore, the rate of exposure is not applicable to the Upper SCR.

Quality-Design - The study included replication and a control treatment, but experimental design/randomization was not clear.

-Analysis - No statistical analysis of the data was conducted.

-Interpretation - No statistical analysis of the data was conducted. It is unclear how the summary figure (Figure 1), which presents soil salinity growth reduction thresholds and LD50 values by species, was constructed from the data. It appears that three soil salinities were established as treatments, but it is not clear if there may have been sufficient variation in the level of soil salinity among the field plots to allow determination of the salt tolerance of a given species at an intermediate soil salinity value. Mean soil salinity values were given as 1.0, 4.3, and 7.0 millimho per centimeter (mmho/cm), but growth reduction values were shown on Figure 1 at a number of intermediate values.

-Conclusion - The conclusions were carefully limited to the relative tolerance of the species examined in terms of soil ECe thresholds.


Study Scope

322.) Francois and Clark 1978


Nursery Crops

-Implementation - A fair discussion of study implementation was presented, but it is not possible to determine the real leaching fraction used or variability of soil salinity across the plots and width depth.

-Duration - The study lasted 2.5 years, which is reasonable for the study objectives.

-Review - This paper was published in a major journal, so thorough peer review can reasonably be assumed.


The author is a local industry expert with Bordiers, a large nursery with operations in Irvine and Somis. He is recognized for his expertise with nursery water quality issues by Bill Darlington and Upper SCR nursery industry extension experts.

Applicability - Bordiers has operations very close to the Upper SCR, in Somis, and apparently Mr. Gutman works with Bordiers operations to manage soil and water quality issues. Therefore, his opinions and experience have to be considered highly applicable for all criteria.

Quality - There was no study design or implementation to evaluate. In general, the author’s major conclusion relative to the Upper SCR was that damage can occur with sensitive plants grown in the area at 3 meq/L (107 mg/L) with sprinkler irrigation. His conclusion was not tied to any specific trials in the area.


Study Scope

316.) Gutman 2004


Nursery Crops


Scope-Osmotic effect - The study measured and correlated EC of solutions and ET, but there were no measurements of relative irrigation water potential and plant tissue water potential.

Applicability-Location and climate - The study was done in Virginia, far different from the Upper SCR climate and soils.

-Rootstock - It can be reasonably assumed that rootstock differs from Upper SCR varieties.

-Irrigation water quality - The study used synthetic seawater for some reason (dominated by NaCl), giving the water dissimilar relative proportions compared to the Upper SCR.

-Irrigation management - No drainage was provided from the containers, but they added demineralized water to maintain soil moisture within a defined range. Soil salinity at harvest was measured.

-Routes of exposure – The route of exposure was through irrigation, so it is reasonably applicable; however, it is not a factor in the study conclusions.

-Rate of exposure - Saline irrigations were applied in four applications separate from normal irrigations over the 4-month monitoring period. The rate of exposure was very artificial compared to the Upper SCR.

Quality-Design – This was a randomized complete block design, with five replications, control, and two varieties; therefore, all of the elements were covered. However, the control solution was demineralized and, therefore, not a realistic condition. This likely also adversely affected plant nutrition for the control. Interactions among constituents cannot be determined from this type of control.

-Analysis - There was no statistical analysis of the data.

-Interpretation - There was no statistical analysis of the data. In addition, the study collected no data on plant tissue concentrations, but leapt to the conclusion that limitations on water uptake was the major impact of increased salinity, and that specific ion toxicity was at most a contributing factor. The authors base this on the results of Lunt et al. (1957), who found azaleas not especially sensitive to Cl. They say nothing about camellias.

-Conclusions - They conclude that 3 mmho/cm soil salinity is the permissible limit for azaleas and camellias, even though some evidence of damage was seen at 2 mmho/cm. Any damage would probably not be acceptable for production of ornamental species for wholesale or retail sale, so this conclusion seems flawed, at least in the context of the needs of Upper SCR nurseries.

-Implementation - Very little detail was given on irrigation; how much or how often irrigation was applied is unknown.

-Duration - The study lasted approximately 4 months, which is reasonable for the species examined.


Study Scope

305.) Lunin and Stewart 1961


Nursery Crops


Scope-Specific ion toxic effect - The study included treatments that were at least very roughly isosmotic (e.g., 25 meq/L versus 25 mg/L) to examine effects based on salt composition, but their focus was nutrient imbalance rather than specific ion toxicity. Specific ion toxicity was never discussed specifically in the experimental design. The authors concluded from their results that there was no evidence that Cl was harmful at 25 meq/L (888 mg/L). Although their focus was nutrient imbalance, their conclusions imply that they considered toxic effect as within their scope. This was not really a specific ion toxicity study.

-Osmotic effect - Osmotic effect was not specifically discussed or tested. They tested a series of increasingly concentrated nutrient solutions, but no evaluations or measurements relative to water potential inside or outside the plant were made.

Applicability-Location and Climate - The study appears to have been done at the University of California – Los Angeles (UCLA), but the location was not clearly described. However, the location did not appear to be significant relative to study conclusions.

-Soils - The plants were potted in peat, and artificial soils were commonly used. This is applicable to the project, but not key to the study conclusions.

-Rootstock - The rootstock is not critical to the study conclusions, but one can assume that although the study is old, studies at UCLA would use applicable varieties for the Upper SCR.

-Irrigation water quality - The information in the source was vague, and salt solutions had a highly artificial composition.

-Irrigation management - One of two experiments provided some information. Too little information was provided to determine applicability.

-Routes of exposure - Cl was applied through irrigation; therefore, it is applicable, but not a part of study conclusions.

-Rate of exposure - No gradual increase was applied, and salt doses were not pulsed; therefore, it is applicable, but was not key to the study conclusions.

Quality-Experimental design - Controls, replication, and randomization were present.

-Analysis - No statistical analysis of the data was provided. Sample size was marginally adequate, with three replications in the first study and six replications in the second study.

-Interpretation - Although there was no statistical analysis, the interpretation of the data was sound given their major objective of determining nutritional imbalances.

-Conclusions - The conclusions followed from the results. They showed that azaleas were not especially sensitive to Cl at 886 mg/L. They showed that high levels of bicarbonate increase Na uptake, and decrease calcium uptake, unless calcium concentrations are high.


Study Scope

303.) Lunt et al. 1956


Nursery Crops

-Implementation - No information was provided on the method of irrigation or how much light was available in the greenhouse. For the first experiment, data were only provided on EC and pH of drainage, not of influent water.

-Duration - The 4 months for Experiment 1 and 8 months for Experiment 2 seem reasonable for the plant and the objectives.

-Level of review - This source was published in a scientific journal.


Nursery Crops


Scope-Specific ion and osmotic effect - Neither specific ion nor osmotic effect were a part of the experimental design. The authors inferred that Cl toxicity was important from their data and a prior study suggesting that high leaf Na was not a problem. This was not justifiably a specific ion toxicity or osmotic effect source.

Applicability-Location and climate - The study was conducted at a UCLA greenhouse; therefore, it is applicable, but not part of the study conclusions.

-Irrigation method – “Surface irrigation” is assumed to mean soil applied, but it is not clear from the text. Small container material is nearly always sprinkler irrigated in the Upper SCR; therefore, it is not applicable.

-Soils - Sand and peat are representative of the porous soil mixes used in container production in the Upper SCR, but not a part of the study conclusions.

-Rootstock -We can reasonably infer that species selected for use at UCLA are representative of Upper SCR. The study conclusions are very specific to varieties tested.

-Cultural practices - Little information was given regarding cultural practices.

-Irrigation management - Watering one to two times per day is representative of the Upper SCR, but not a factor in the study conclusions.

-Routes - Root uptake is representative of the Upper SCR, but foliar uptake would have to be considered a factor with flower production.

-Rate of exposure - Water was applied with each irrigation without ramp-up; therefore, it is applicable, but not a factor in the study conclusions.

Quality-Design - All elements were included: completely randomized design, three replications, and control.


-Interpretation - Minimal interpretation of the data was provided, with no statistical analysis.

-Conclusion - Conclusions were carefully limited to the species and varieties tested, and reasonably followed from experimental results. The varieties tested were very sensitive to the salt solutions used, which was clear from the data.

-Implementation - There was a reasonable record of implementation, with only limited questions by the evaluator regarding timing, approach, and milestones. Soils or, at least, leachate data should have been collected. No information was provided on the rate of progression of the visible effects on plant appearance and growth.

-Duration - A 7-month duration for herbaceous species-like flowers is reasonable.



Study Scope

313.) Lunt et al. 1957


Nursery Crops

-The major limitation of this source is that the lowest concentration of Cl used was 1,418 mg/L, and adverse effects were apparent at that level. The actual threshold for adverse effects from the salt solutions used cannot be determined from these data.


This article is a widely referenced summary of salt-tolerance thresholds for a wide range of crops, including ornamental species.

Scope-Specific ion versus osmotic - The source discussed specific ion toxicity, but not osmotic effect. It did not discuss Cl toxicity and ornamentals specifically, nor did it discuss the relationship of ECe data to Cl toxicity with ornamentals.

-Crop appearance - The source discussed the importance of appearance with ornamental species.

Applicability-Location and climate - The ornamental studies summarized were conducted at USSL.

-Irrigation method - No irrigation method was described in this source.

-Soils - No information regarding soils was provided in this source.

-Rootstock - The species discussed are relevant to the Upper SCR.

-Cultural practices - No information regarding cultural practices was provided in this source.

-Irrigation management - No information regarding irrigation management was provided in this source.

-Routes of exposure - Relative plant tolerance was based on soil ECe; therefore, results are relevant when compared to drip-irrigated nursery stock.

-Rate of exposure - No information regarding rate of exposure was provided in this source.

Quality-Conclusion - The summary of USSL test data was reasonably thorough. No specific data on Cl thresholds for nursery crops were provided; thresholds were only based on ECe data. Review of the suggested 10X conversion of ECe data to Cl thresholds reveals that this conversion applied to “most non-woody” crops, and was not specificallytied to nursery crops. The 10X factor was also for estimation of Cl in the saturation extract, and not at field capacity.

-Review - The review typical of a journal paper is assumed.


Study Scope

318.) Maas 1986


Nursery Crops


The source provided a short review on plant physiology of Cl as a nutrient and toxicant.

Scope-Specific ion versus osmotic - The review described general processes of specific ion toxicity (species and variety differences in transport to shoot) and Cl as a contributing ion to osmotic effects.

Applicability-Routes of exposure - No information was provided on other aspects of applicability. The discussion on root uptake suggests it is applicable to the Upper SCR.

Quality-Conclusion - No thresholds were provided or other literature to support processes described, but the review on toxicity and specific ion toxicity and osmotic effects was consistent with the bulk of other literature.

-Review - It can be reasonably assumed that the source was subject to review because of the source in which it was published.


Study Scope

317.) Maas 1987


This is the most complete review of salt-tolerance data known covering a wide range of crops. It closely parallels the 1986 review by the same author.

Scope-Specific ion versus osmotic - The source covers both issues in introductory material, and concludes that ECe data can be directly related to Cl tolerance where experiments were conducted using salts with Cl as the dominant anion.

Applicability-Location and climate - Ornamental crop experiments were conducted at USSL in Riverside, California and, therefore, are applicable and relevant to the study conclusions.

-Rootstock - The species of rootstock used is commonly grown in California, and integral to results reported.

-Routes of exposure - Thresholds given were based on soil ECe, and therefore applicable to drip-irrigated operations in the Upper SCR, and relevant to the study conclusions.

Quality-Conclusion - The summary of USSL test data was reasonably thorough. No specific data on Cl thresholds for nursery crops were provided; thresholds were only based on ECe data. The author suggested a 10X conversion of ECe data to determine Cl thresholds. Unlike the 1986 review, Maas did not limit the applicability of this conversion to “most non-woody” crops, suggesting it has broad applicability for salt-tolerance tests conducted primarily with Na and calcium Cl salts. The 10X factor was also for estimation of Cl in the saturation extract, and not at field capacity.

-Review - The work was published as a chapter in ASCE Manual; therefore, considerable review can be reasonably assumed.


Study Scope

319.) Maas 1990


Nursery Crops


Scope-Specific ion versus osmotic - These issues were not laid out in objectives, interpretations, or conclusions in any significant way.

Applicability-Location and climate - The study was conducted in Logan, Utah, and results are thus not especially applicable to the Upper SCR.

-Irrigation method - The irrigation method was obscure from reading this source alone; thus, it was rated zero. It is highly likely that the study used flood irrigation based on a 1961 paper and the use of level basins, but we cannot be certain.

-Soils - A good description of soils was provided, but soils are not comparable to the Upper SCR use of porous materials in containers.

-Rootstock - Predominantly northern latitude or higher elevation species were studied, including Douglas fir, blue spruce, honey suckle, and green ash; thus, rootstocks used are not relevant to the Upper SCR.

-Cultural practices - The study did not use containers; thus, cultural practices are not very applicable to the Upper SCR.

-Irrigation management - Irrigation was provided once per week and is not applicable to the Upper SCR.

-Routes of exposure - The study used soil-applied irrigation, making it applicable to the Upper SCR; but it was not tied to the study conclusions.

-Rate of exposure - A stepwise increase in salinity was used, making it not applicable to the Upper SCR.

Quality-Design - The study incorporated completely randomized design, four replications, and a control treatment; thus, all basic elements were incorporated.


-Interpretation - No statistical analysis was provided.

-Conclusion - Conclusions followed from experimental results. The main objective of the study was to determine relative tolerance, and conclusions were generally limited to this realm. They acknowledged that a 1.5-year study is not definitive for long-lived species, where cumulative effects could become important.

-Implementation - In general, this source provided more complete information on implementation than most papers of the late 1950s and early 1960s. No data were collected on Cl levels in plant tissue, and no soils data were collected. No clear explanation of their irrigation rate was provided, which was based on an “excess of salt” solution, which was not defined. It appears that they applied a sufficient volume to obtain a leaching fraction that would prevent a continual accumulation of salt, but this cannot be determined from the source.

-Duration - A 1.5-year study is probably appropriate to determine gross-level differences in a range of species and to identify potential differences in uptake of salt constituents, which were their objectives.


Study Scope

314.) Monk and Peterson 1962


Nursery Crops

-Review - The typical review of a journal paper is assumed.

-An important overall limitation for this study for the purposes of the Upper SCR is that the lowest salt treatment was still very high in salinity and Cl, at 4,000 ppm (2,500 mg/L Cl). The range of salinities used provided some indication of the threshold for only the most salt-tolerant species in the study. Sensitive species were heavily damaged at the lowest salinity treatment.


Nursery Crops


This Utah study was conducted to evaluate the relative salt tolerance of numerous ornamental plant species, and to examine correlations with protoplasmic (cellular level) salt hardiness.

ScopeGrowth stage, growth impacts, specific ion toxicity, osmotic effects, water duties, Cl toxicity mechanisms, and seasonal Cl variation were not within the scope of this study.

Applicability-Location and climate - The study was conducted in Utah; thus, it is only moderately relevant to the Upper SCR.

-Irrigation method and cultural practices - The field experiment was conducted using flood irrigation, which is not used in Upper SCR nursery practice. Experiment 2 was conducted using a hydroponic study, which is even less applicable to Upper SCR nursery practice. Experiment 3 was conducted using excised plant tissue sections, even further removed from Upper SCR practice.

-Soils - No information regarding soils was given.

-Rootstock - Woody plants used in field study are not applicable to the Upper SCR (ponderosa pine, green ash, blue spruce, eastern red cedar, and honey locust). Herbaceous flowers used in the hydroponic study might be more applicable.

-Irrigation management - Essentially no information was provided for Experiment 1 (field), and a weekly change of hydroponic solution was provided in Experiment 2.

-Routes of exposure - Uptake through roots in Experiments 1 and 2, but not Experiment 3, was documented.

-Rate of exposure - Salt concentrations were increased gradually in the field experiment, which is not relevant to the Upper SCR.

Quality-Design - Field and hydroponic experiments were completely randomized designs with four replications and control; thus, all elements were present.

-Analysis - Only summary data were presented; no statistical analysis was presented.

-Interpretation - Only general conclusions relative to salt tolerance were drawn, with no statistical analysis. Most of the discussion related to technical details of the protoplasmic studies.

-Conclusions - Conclusions were limited to lists of relative salt tolerance among species tested and correlations of field and hydroponic studies with plant tissue (protoplasmic) tests. Conclusions followed from experimental results, and no uncontrollable factors were known to have affected experimental results. No conclusions relative to Cl were drawn.

-Implementation - The evaluator has numerous questions about how this study was conducted. The most important follow: How long were the salt treatments applied in the first year? When did they start the second growing season? What kind of soil was present in the field plots? How was irrigation managed? How did soil salinity vary throughout the study?


Study Scope

310.) Monk and Wiebe 1961


Nursery Crops

-Duration – One and one-half growing seasons is reasonable for field studies; very few studies extend this long or longer. Three months appears appropriate for herbaceous species (flowers).

-Review - This source was published in the major journal “Plant Physiology.”


Scope-Specific ion toxicity - The source stated that Cl can be directly toxic.

-Osmotic effect - The source stated that high EC can impede water uptake, but did not really discuss osmotic impacts directly.

Applicability-Location and climate - This source was an Arkansas guidance document.

-Soil type - This source described artificial soils (peat mixes) typical of greenhouse operations.

-Cultural practices and irrigation management - This source described water treatment and irrigation management methods that are relevant, but these are not tied to source’s recommendations regarding Cl.

Quality-Miscellaneous concerns - The study provided no specific guidance on thresholds or management for drip versus spray irrigation. Cl thresholds given were provided with no explanation or references to experimental results. No discussion of differences in tolerances among nursery crop species was provided.


Study Scope

304.) Robbins and Klingaman 2000


This source is a brief extension or industry bulletin from Australia.

ScopeThe source specifically described specific ion effect as a concern, but did not address osmotic effect at all.

Applicability-Location, climate, and soils - These were not discussed specifically, but it can be reasonably inferred that the information applies to Australia.

Quality-Conclusions - The document provided recommendations on Cl thresholds, but these values were not linked to any specific research studies, irrigation method, or plant; therefore, the values are of limited value.


Study Scope

308.) Stephens 2002


Nursery Crops


Scope -Specific ion toxic effect versus osmotic - This source appears to assume that specific ion effects were the causal mechanism, but osmotic versus ion effects were not specifically discussed. The source focused on relative growth, visible leaf effects, and elemental distribution in stems and leaves.

Applicability -Irrigation method, soil type, and irrigation management - Irrigation was through hydroponic culture, including a weekly change of the solution; thus, this criteria was given a low score because nursery crops in the Upper SCR are not generally grown hydroponically.

-Location and climate - The study was conducted in Ohio.

-Species - The study included white pine, pin oak, and honey locust. These species are not applicable for nursery practice in the Upper SCR.

-Routes of exposure - The roots did have access to salts; thus, the route of exposure is at least somewhat applicable to the Upper SCR. This is not a factor in the study conclusions.

-Rate of exposure - Salt treatments were not ramped up or pulsed, making the rate of exposure at least somewhat applicable to the Upper SCR.

Quality-Experimental design - The study had adequate controls, randomization, and replication.

-Analysis - The study appears to have a complete data set. The authors exhaustively explored the data, and the statistical analysis seems to be appropriate for the experimental design.

-Interpretation - The interpretation of the statistical results was thorough and correct.

-Conclusion - Conclusions followed from the interpretation of the results. No uncontrollable factors were known to affect the results.

-Implementation - A reasonable level of detail was provided on timing, approach, and milestones. The evaluator’s only reservation pertains to the lack of description for the level of light in the greenhouse.

-Duration - The study was rated a 2, indicating that the duration meets some objectives. The 5-week exposure period was probably enough to provide some initial screening-level data, but in evaluator’s opinion is not sufficient to determine definitive differences in salt tolerance among these species.

-Review - This source was published in a major horticultural journal, so adequate peer review can reasonably be assumed.


Study Scope

301.) Townsend 1980


Nursery Crops


This source presented a greenhouse study of reuse of potassium Cl-based water softener regenerant on landscape plants using sprinkler irrigation.

Scope-Specific ion versus osmotic - Ion uptake issues were a major focus of this source, and the fact that no Na salts were used strengthens the case for specific ion toxicity from Cl. No discussion or experimental methods were used to evaluate the osmotic stress issue.

Applicability-Location and climate - Tests were conducted at the University of California - Davis (UC Davis) and are, therefore, somewhat applicable to the Upper SCR, but not directly related to the study conclusions.

-Irrigation method - Sprinkler irrigation of containers was used and is, therefore, highly relevant to the Upper SCR, but not directly related to the study conclusions.

-Soils - A mixture of sand, peatmoss, and redwood sawdust was used; therefore, the study is relevant to container production in the Upper SCR, but not directly related to the study conclusions.

-Rootstock - Species relevant to the Upper SCR included pittosporum, azaleas, and others. These were selected for the study because they are “commonly grown in gardens of California.”

-Cultural practices - Too little data were presented to make an evaluation.

-Irrigation management - Wastewater was applied two times each week, and fresh water was applied one time each week, for a total of 1 inch each irrigation. Frequency of irrigation is probably reasonable for established landscapes, but probably low compared to nursery container production.

-Routes of exposure - Sprinkler application was used; therefore, both soils and roots were exposed and, thus, relevant to Upper SCR production. This is not directly related to the study conclusions.

-Rate of exposure - As according to irrigation management, application of saline wastewater was interspersed with applications of fresh water, and, therefore, not applicable to Upper SCR nursery practice.

Quality-Design - Randomized block design with low salinity control and three replications was used; therefore, all elements were present.

-Analysis - Unlike nearly all of the other studies, a statistical analysis was conducted, including ANOVA, to test for the significance of variation among species, irrigation treatments, and interactions. Duncans Multiple Range test was used to determine if differences were significant among species. Correlations among key factors were also considered. The analysis seems appropriate and thorough.

-Interpretation - The interpretation of the data incorporated statistical methods, but some interpretations were questionable. The correlations among relative growth, tissue Cl, and tissue calcium/Cl were very weak, indicative of the significant variations among the different species.

-Conclusion - The major objectives of the source were to examine plant growth and ion uptake differences. The majority of their conclusions can be supported by their data and analysis. The authors made too much of


Study Scope

324.) Wu et al. 1995


Nursery Crops

the weak correlations without providing an adequate physiological explanation for their link between calcium and Cl. They did not really prove experimentally that high tissue calcium is the protective mechanism for tolerant species, and did not provide citations from the literature to support this conclusion. They did adequately make the case that differences in Cl uptake led to differences in plant growth.

-Implementation - The source provided a better than average documentation of greenhouse conditions and analytical methods.

-Duration - Two 12-week growth periods appear to be adequate for the objectives of the source.


-A significant limitation of this source is that the lowest concentration of Cl evaluated was 1,484 mg/L. Effects on the most sensitive species were severe; thus, all that can be determined is that the threshold value for Cl is something less than 1,484 mg/L for the most sensitive species.


Nursery Crops


This source summarized studies conducted at UC Davis on recycled water salinity impacts on ornamental species, with sprinkler versus drip irrigation.

Scope-Specific ion versus osmotic - Separation of osmotic versus specific ion effects was not within the scope of the study, other than the correlation of tissue Cl and Na concentrations versus visible effects.

Applicability-Location and climate - The studies were conducted at UC Davis and are, therefore, at least somewhat similar in climate and growing conditions to the Upper SCR, but are not key to the study conclusions.

-Irrigation method - Both sprinkler and drip irrigation were used, making the method applicable to the Upper SCR and crucial to the study conclusions.

-Soils - Field studies were conducted in a loam clay (sic) soil, and greenhouse studies were conducted using a mixture of sand, peat, and redwood sawdust. Therefore, greenhouse studies are reasonably applicable to container culture in the Upper SCR, but field studies are not. Soils issues were not crucial to study conclusions.

-Rootstock - Species selection was based on popularity in California landscaping, and therefore is applicable; differences among these species were fundamental to the study’s conclusions.

-Cultural practices - Relatively little data regarding cultural practices were provided to evaluate.

-Irrigation management - Irrigation frequency in the greenhouse was 3 times each week to the point of free drainage, but irrigation practices in the field study are not clear from the source. Irrigation management other than the irrigation method was not a key factor in the study’s conclusions.

-Routes of exposure - Exposure was both through roots and leaves, and therefore is applicable to the Upper SCR. Route of exposure was also key to the study’s conclusions.

-Rate of exposure - No ramping or pulsing of saltwater flows was used; therefore, rate of exposure is applicable to the Upper SCR, although not key to the study conclusions.

Quality-Design - The study was randomized among blocks, replicated, and control used; thus, all essential elements were present.

-Analysis - ANOVA was used to determine if factors such as plant species, rinsing versus not rinsing sprinkler-irrigated leaves, and sprinkler versus drip irrigation were significant sources of variation for individual experiments, which appears to be a valid approach. Mean and standard deviations for individual observations were reported. The study lacked a complete exploration of the data, in that the significance of treatment effects within individual plant species was not examined.

-Interpretation - Interpretation of the data incorporated some statistical methods, and the interpretation was fairly well documented. Table 3 in the source provided a summary of “spring” plant growth and symptoms of salt stress, but the timing of the observations and duration of salt exposure at the time the observations were made is not clear. Tables that appear to be closely related (4 and 6) do not include all of the same species,


Study Scope

325.) Wu et al. (b) 2001


Nursery Crops

and this is confusing.

-Conclusion - Most of the major conclusions of the source were supported by the data and analysis. The conclusion the evaluator questions is the utility of sprinkler irrigation as a predictive tool to assess plant tolerance, such as for plant screening. The authors did not reference any supporting literature, and Maas (1990) clearly lays out the reasons why tolerance to root-zone salinity may not be very well correlated with tolerance to sprinkler irrigation using water with elevated salts. Moreover, the authors largely based this conclusion on a small study including only four landscape species.

-Implementation - The source is difficult to follow, raising concerns with implementation. It takes some effort to be certain which of the subexperiments is being discussed. It is not clear from the text how the plants in the greenhouse study were irrigated, and the purpose and meaning of the greenhouse study is not clear from the source. Irrigation frequency is confusing, because the authors first state that irrigation adjusted for the weather, and later state that it was continued regardless of the weather. Figure 2 was important to the conclusions of the study, and there were obvious errors in the figure caption that raise questions about the data presented. Liquidambar and oleander were clearly reversed in terms of their salt tolerance.

-Duration - The duration of the individual studies appears to be appropriate to meet the objectives of the study.


-A limitation of this source for determination of acceptable Cl thresholds is the fact that only relatively high concentrations were used. The low salinity treatment had a Cl concentration of 300 mg/L, and the high salinity treatment had 900 mg/L Cl. Moreover, the salt treatments were applied as NaCl, without any Ca salts, which may limit the applicability of the results.


Nursery Crops


This source briefly summarized a greenhouse study of ion uptake differences among five herbaceous ornamental species using a simulated wastewater.

Scope-Specific ion versus osmotic - No specific tests were used to evaluate specific ion versus osmotic effects other than measuring plant tissue Cl.

Applicability-Location and climate - The studies were conducted at UC Davis, but were not directly related to the study conclusions.

-Irrigation method - No information regarding irrigation method was given.

-Soils - No information regarding soils was given.

-Rootstock - Rootstock was selected based on “commonly grown in California gardens and landscapes.” Therefore, this is applicable to the Upper SCR and related to the study conclusions.

-Cultural practices - Essentially, no information regarding cultural practices was given.

-Irrigation management - Salt water was applied two times each week, and fresh water one time each week. No information on volumes or rates applied was provided.

-Routes of exposure - Not enough information was provided to determine the routes of exposure used.

-Rate of exposure - A pulsed approach with freshwater flushes was used and is not applicable to the Upper SCR.

Quality-Design - The authors describe a control, but no experimental design, randomization, or replication was described.

-Analysis - The source lacked complete exploration of the data, and it is impossible to determine if the ANOVA results presented are appropriate without more information on the experimental design.

-Interpretation - There was only minimal interpretation of the data as regards Cl. Potassium, magnesium, calcium, and Na interactions and physiological considerations were explored in much greater detail than Cl.

-Conclusion - Conclusions regarding Cl were provided, but were rather vague and limited.

-Implementation - Minimal information was provided about study implementation. No data were provided about greenhouse conditions, depth of watering, or fertilization. Most importantly, the study described preparation of three dilutions of a simulated recycled water solution, but it is impossible to determine which dilution was represented in the study results.

-Duration - The 6-month study duration seems appropriate for the herbaceous species used in the study.

-Review - Review typical of an agency report is assumed.


Study Scope

328.) Wu et al. (Slosson) 1998


Nursery Crops


This source is another paper in a series describing results of studies conducted at UC Davis on salt tolerance of ornamental species, using drip and sprinkler irrigation.

Scope-Specific ion versus osmotic - No specific experiments were conducted other than collecting some data on leaf Cl and Na levels.

Applicability-Location and climate - The experiments were conducted at UC Davis and are, therefore, applicable to the Upper SCR, but they are not directly related to the study conclusions.

-Irrigation method - Drip and sprinkler irrigation were evaluated, and results are directly related to the study conclusions.

-Soils - Yolo loam for field plantings and a typical container mixture of sand/peat/redwood sawdust for field container studies and greenhouse studies were used. Container soils are relevant to the Upper SCR, but are not directly related to the study conclusions.

-Rootstock - A wide range of species were used, and were selected based on their popularity in California gardens and landscapes. Rootstock was applicable and relevant to the study conclusions.

- Cultural practices - Not enough data on cultural practices were presented to evaluate.

-Irrigation management - Information on irrigation management was limited, but, in general, plants were liberally watered, approximately 3 times each week other than in the wettest part of the winter. Irrigation management appears to be reasonably applicable to the Upper SCR, but not directly related to the study conclusions.

-Routes of exposure - Because both drip and sprinkler irrigation were used, these factors are relevant to Upper SCR nursery production. Sprinkler versus drip irrigation tolerance issues were important to the study’s conclusions.

-Rate of exposure - It does not appear that salt solutions were gradually implemented or applied periodically; therefore, this factor is relevant to the Upper SCR, but not key to the study conclusions.

Quality-Design - Greenhouse and rapid assessment method studies included all elements (RCB design, control, and replication). The experimental design of the field studies is not clear from the source, and the major conclusions of the source were most critically related to these experiments; therefore, this factor is given a rating of 2.

-Analysis - The only statistical analysis that was reported in the source was Na and Cl leaf tissue concentrations for a subset of the plants (results for five plants reported) used in the field study. Data were reported after 6 weeks of salt exposure in a multi-year study. Therefore, some analysis was conducted, but the level of analysis is clearly lacking complete exploration of the data and appropriate analysis.

-Interpretation - There was only minimal interpretation of the data, and only general conclusions were drawn. Some of the most important data collected (final evaluations of growth and evidence of salt stress after 6 or 22


Study Scope



Nursery Crops

months of exposure) were not presented in any table or figure, but were only summarized in the text.

-Conclusion - Major conclusions of the study were described, and the majority follow from the interpretation of study results (such as, they were vague or not shown, and little if any statistical analysis. A significant limitation of the conclusions is the correlation the study attempts to make between drip and sprinkler irrigation salt-tolerance results. The source did not adequately make this case, and did not discuss any results from other studies that showed that these factors might not necessarily be closely related. They did provide the qualifying word “may,” when describing the potential utility of the rapid screening method. They suggest using relatively high salinity sprinkler irrigation.

-Implementation - The source was relatively short, considering it provided some information on methods and results from five separate experiments. A number of important details on study implementation were either not described or not described in sufficient detail to understand or evaluate. The method of irrigation used in the greenhouse study was not given, yet this study drove one of the major conclusions of the source, relating drip irrigation salt-tolerance data with sprinkler irrigation tolerance. The greenhouse study also justified using the results of the rapid screening trial described in the source. Start and stop dates for experiments were vague. No analytical data were provided on the control treatment (potable water). Irrigation management for the initial phase of the field experiment was not well described.

-Duration - The study duration appears applicable for all study objectives.


Nursery Crops


This source presented a report of a field demonstration with the City of San Jose.

Scope-Specific ion versus osmotic - No data were collected or interpretations made beyond observing leaf tissue Cl levels.

Applicability-Location and climate – The study was conducted in San Jose, California, and is, therefore, applicable to the Upper SCR, but not directly related to the study conclusions.

-Irrigation method - Sprinkler irrigation was used, making the method applicable and relevant to the study conclusions.

-Soils - No information regarding soils was provided.

-Rootstock - Species were selected by Wu and the San Jose landscape specialist; thus, it can be reasonably assumed they are generally relevant for the nursery industry in California. Species tolerance was a major factor in the study’s conclusions.

-Cultural practices - Little information regarding cultural practices was provided.

-Irrigation management - No information regarding irrigation management was provided.

-Routes of exposure - Foliar exposure was used; thus, it is relevant to the Upper SCR and directly related to the study conclusions.

-Rate of exposure - No discussion of ramped or pulsed exposure approach was provided; therefore, it is relevant to the Upper SCR, but not directly related to the study conclusions.

Quality-Design - No experimental design was described, other than they established a site that received recycled water adjacent to one that received potable water. This appears to be a one-replication study, but it is not clear from the report.

-Analysis - The authors reported that there were significant differences among plants on Cl and Na uptake, and that Na and Cl concentrations in plant leaves were significantly higher than the control. However, not enough information was provided to determine what procedure was used, or if it was appropriate.

-Interpretation - Minimal interpretation of the data was conducted.

-Conclusion - The authors did not observe evidence of salt stress over the course of the experiment, although they found evidence of significant differences in Cl and Na uptake. This conclusion was fairly well documented, other than the concerns expressed regarding the lack of information describing experimental design, analysis, and implementation. They acknowledged the limitations of a 1-year study, and that longer term impacts could emerge.

-Implementation - Data were not provided on the quality of the potable water used, whether the plants were


Study Scope



Nursery Crops

planted or in containers, and when plants were planted. No data were provided on growth, and no information was provided on irrigation frequency or other management.

-Duration - The 1-year duration of the study seems appropriate for the study objectives.



Nursery Crops


-This source provided a summary of soil-planted and container-grown species, comparing drip to sprinkler irrigation with simulated recycled water. The main objectives were to evaluate tolerance of a wide range of species commonly grown in California, and to develop a rapid screening tool to allow assessment of salt tolerance of other potential species.

Scope-Specific ion versus osmotic - Other than collecting leaf tissue data on Cl and Na, no specific data were collected to examine this issue.

Applicability-Location and climate - The studies were conducted outdoors at UC Davis and, therefore, are applicable to the Upper SCR. However, these factors were not directly related to their conclusions.

-Irrigation method - Both sprinkler and drip irrigation were used, and the irrigation method was fundamental to the experimental design and conclusions.

-Soils - Field plantings were made in a loam clay soil (sic), and field-grown container plantings were grown in a peat-sand-redwood sawdust mixture. Therefore, soils could be considered applicable to the Upper SCR, but soil conditions were not a factor in the study’s conclusions.

-Rootstock - Species were selected based on twin objectives of popularity of use in California landscapes and diversity and are, therefore, applicable to the Upper SCR. Species differences in salt tolerance were a factor in study conclusions.

-Cultural practices - Too little data regarding cultural practices were provided to evaluate; this was not a factor in the study conclusions.

-Irrigation management - Irrigation was applied every other day using 1 inch of water, and irrigation was suspended during wet winter weather. This is reasonably applicable to the Upper SCR, but not a factor in the study conclusions.

-Routes of exposure - Both root-zone and foliar applications were used, making them applicable to the Upper SCR and a factor in the study conclusions.

-Rate of exposure - Saltwater solutions were not ramped or pulsed; therefore, this factor is applicable, but not a factor in the study conclusions.

Quality-Design - Three replications, randomization, and low salinity control were involved; therefore, all elements were present.

-Analysis - ANOVA was used to determine if there were differences among means for soil chemical parameters by irrigation method and by soil versus container. ANOVA was also used to determine if there were differences of plant growth among species for both soil- and container-grown plants at each salinity treatment. No comparisons were made of plant growth or visible effects within a species, and the evaluator thinks this represents a lack of complete exploration of the data, especially in light of the authors’ conclusion that salt tolerance to sprinkler irrigation was correlated with root-zone salt tolerance.


Study Scope

326.) Wu et al. (Slosson) (a) 2001


Nursery Crops

-Interpretation - In general, statistical interpretations were interpreted thoroughly and correctly for the tests that were done. The attempt to illustrate correlation in Figure 1 with a line connecting two tightly grouped zones of data is not correct. The figure did not show that salt stress and growth parameters were correlated. The authors state that there was no evidence of salt stress with drip irrigation at 1,500 mg/NaCl; however, their data showed that two plants had 5 to 10 percent of the leaves affected. Even this low level of damage may pose a significant hardship for nursery crop production; however, the focus of this source was really established landscapes.

-Conclusion - The major conclusions of the source generally followed from the experimental results. The evaluator disagrees with the authors’ conclusion regarding the usefulness of tolerance to sprinkler irrigation as a predictive tool for tolerance to soil salinity. This was not really shown by their data and is not supported by other literature. The authors also should have acknowledged that salt tolerance revealed after a 6-week study may not be indicative of longer term effects for some species.

-Implementation - Little data were provided on the chemistry of the control solution. It is not clear when the plants were established in Experiment B, other than “Fall 1998.” The duration of Experiments A and B suggests many months, but data were limited to growth and salt stress effects after 6 weeks. Longer term effects of the salt treatments were not described, and it is unclear whether data were even collected.

-Duration - It appears that the field Experiment A was conducted for two full growing seasons, but all of the data presentation emphasized data after 6 weeks of salt treatment. Field Experiment B was conducted for 1.5 growing seasons, but detailed results were not shown. Results were only shown as an overall summary of relative plant tolerance, which combined all of their data. Field Experiment C was conducted for 6 weeks as a test of the rapid screen technique, and results were similarly only presented as part of the overall summary table of plant tolerance. The authors made predications about long-term performance based on a 6-week test.



Lit

erat

ure

Eva

luat

ion

(o

rgan

ized

alp

hab

etic

ally

)

SCORE (A + Q)

Avo

cad

os

Climate

Irrigationmethod

Soil type

Rootstock, variety, species, & genotype

Culturalpractices

Irrigationmanagement

Routes ofexposure

Rate ofexposure

Location

SCORE

ST

UD

Y A

PP

LIC

AB

ILIT

Y (

Max

imu

m S

core

= 2

7)

Experimentaldesign

Strength ofanalysis

Strength ofinterpretation

Strength ofconclusion

Strength ofimplementation

Study durationappropriate for

study objectives

Level of review

SCORE

ST

UD

Y Q

UA

LIT

Y (

Max

imu

m S

core

= 2

1)

TOTAL SCORE

Typ

e o

f S

tud

y

Growth stage

Yield impact

Source of chloride

Chloride-specificion toxic effect

Irrigation waterrequirement

Osmotic effect

Physical mechanismof chloride toxicity

Fruit quality

Seasonal chloridevariation

SCORE

ST

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CO

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(M

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9)

Exp

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3032

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11

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2326

20

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114

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Aye

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195

119

202

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71

12

22

31

12M

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01

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0

Bar

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997

2630

20

12

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33

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12

32

22

315

San

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40

01

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11

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Ben

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1114

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16

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01

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Ber

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281

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123

251

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320

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116

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2830

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and

Arp

aia,

200

235

362

21

30

22

12

153

33

23

33

20S

and

cultu

re,

outd

oors

10

01

00

00

00

Mon

tgom

ery

Wat

son,

199

737

422

32

33

32

32

233

11

22

32

14F

ield

50

11

01

00

11

Mon

day,

Mar

ch 2

1, 2

005

Page

1 o

f 4

Lit

erat

ure

Eva

luat

ion

(o

rgan

ized

alp

hab

etic

ally

)

SCORE (A + Q)

Avo

cad

os

Climate

Irrigationmethod

Soil type


Culturalpractices


Routes ofexposure

Rate ofexposure

Location

SCORE

ST

UD

Y A

PP

LIC

AB

ILIT

Y (

Max

imu

m S

core

= 2

7)

Experimentaldesign

Strength ofanalysis





study objectives

Level of review

SCORE

ST

UD

Y Q

UA

LIT

Y (

Max

imu

m S

core

= 2

1)

TOTAL SCORE

Typ

e o

f S

tud

y

Growth stage

Yield impact

Source of chloride



Osmotic effect


Fruit quality


SCORE

ST

UD

Y S

CO

PE

(M

axim

um

Sco

re =

9)

Ost

er a

nd A

rpai

a, 2

002

2831

22

23

03

23

219

21

11

12

19

Fie

ld3

01

10

10

00

0

Ost

er e

t al.,

198

815

172

00

30

01

00

61

11

11

31

9G

reen

hous

e2

00

11

00

00

0

Pat

el e

t al.,

197

620

212

01

10

01

32

102

12

23

00

10C

onta

iner

, gre

enho

use

10

01

00

00

00

Sal

azar

-Gar

cia

and

Cor

tes-

Flo

res,

198

815

161

11

10

02

01

70

11

21

21

8M

ensu

rativ

e1

00

00

00

00

1

Sal

azar

-Gar

cia

and

Larq

ué-S

aave

dra,

198

514

160

01

10

02

10

53

11

12

01

9G

reen

hous

e2

00

10

00

10

0

Wie

sman

, 199

525

281

01

10

02

11

72

33

23

23

18G

reen

hous

e3

00

11

00

10

0

Rev

iew

Pub

licat

ions

Am

rhei

n, 1

999

2328

33

03

32

23

221

00

11

00

02

Rev

iew

of o

ne s

tudy

50

11

10

10

10

Aye

rs a

nd W

estc

ot,

1985

912

00

03

03

00

06

00

00

00

33

No

stud

y3

00

11

01

00

0

Ben

-Ya'

acov

, 197

62

20

00

00

00

00

00

01

10

00

2N

o st

udy

00

00

00

00

00

Ber

gh, 1

967

99

30

00

30

00

39

00

00

00

00

No

stud

y0

00

00

00

00

0

Coo

per

et a

l., 1

952

1010

00

00

00

00

00

22

11

21

110

Rev

iew

00

00

00

00

00

Fab

er, 2

004

1922

33

00

03

23

216

00

00

00

33

No

stud

y3

00

10

10

00

1

Gaz

it an

d K

adm

an, 1

976

56

00

00

00

00

00

00

22

00

15

No

stud

y1

00

10

00

00

0

Gra

ttan

and

Ost

er,

2002

1114

20

01

02

02

29

00

00

00

22

No

stud

y3

00

11

01

00

0

Gre

enw

ay a

nd M

unns

, 19

809

120

00

00

00

00

00

22

20

03

9N

o st

udy

30

00

10

11

00

Gus

tafs

on,

1976

66

03

00

03

00

06

00

00

00

00

No

stud

y0

00

00

00

00

0

Haa

s, 1

928

66

20

00

02

00

26

00

00

00

00

No

stud

y0

00

00

00

00

0

Laha

v an

d A

ycic

egi-L

owen

gart

, 200

316

161

30

10

32

01

110

02

20

01

5R

evie

w o

f stu

dies

00

00

00

00

00

Maa

s, 1

990

811

00

03

00

00

03

00

20

00

35

No

stud

y3

00

11

01

00

0

Ost

er, 2

002

914

20

01

00

00

25

00

21

00

14

Rev

iew

of s

tudi

es5

01

11

11

00

0

Par

tida,

200

215

172

00

23

22

22

150

00

00

00

0F

ield

stu

dies

rev

iew

20

10

01

00

00

Sha

lhev

et, 1

999

1620

03

03

03

33

015

00

00

00

11

No

stud

y4

01

10

10

10

0

Sha

lhev

et, 1

994

1417

12

01

13

23

114

00

00

00

00

Rev

iew

of s

tudi

es3

10

11

00

00

0

Tho

mas

, 193

29

103

00

00

30

03

90

00

00

00

0P

erso

nal e

xper

ienc

e1

00

10

00

00

0

Tra

sk, 1

960

1314

31

10

03

11

313

00

00

00

00

Per

sona

l exp

erie

nce

10

01

00

00

00

Mon

day,

Mar

ch 2

1, 2

005

Page

2 o

f 4

Lit

erat

ure

Eva

luat

ion

(o

rgan

ized

alp

hab

etic

ally

)

SCORE (A + Q)

Str

awb

erri

es

Climate

Irrigationmethod

Soil type


Culturalpractices


Routes ofexposure

Rate ofexposure

Location

SCORE

ST

UD

Y A

PP

LIC

AB

ILIT

Y (

Max

imu

m S

core

= 2

7)

Experimentaldesign

Strength ofanalysis





study objectives

Level of review

SCORE

ST

UD

Y Q

UA

LIT

Y (

Max

imu

m S

core

= 2

1)

TOTAL SCORE

Typ

e o

f S

tud

y

Growth stage

Yield impact

Source of chloride



Osmotic effect


Fruit quality


SCORE

ST

UD

Y S

CO

PE

(M

axim

um

Sco

re =

9)

Exp

erim

enta

l Stu

dies

Bro

wn

and

Vot

h, 1

955

1314

01

11

00

00

14

01

11

13

29

Fie

ld1

01

00

00

00

0

Ehl

ig, 1

961

2223

01

01

01

13

07

31

12

32

315

Aqu

acul

ture

10

01

00

00

00

Ehl

ig a

nd B

erns

tein

, P

art A

, 19

5818

220

00

10

10

10

32

21

22

33

15F

ield

and

san

d cu

lture

40

01

11

10

00

Ehl

ig a

nd B

erns

tein

, P

art B

, 19

5820

230

01

11

00

10

43

21

22

33

16F

ield

30

11

00

00

10

Giu

ffrid

a et

al.,

200

120

241

00

10

10

11

52

32

22

31

15A

rtifi

cial

med

ia/a

quac

ultu

re4

01

10

10

01

0

Han

sen

and

Ben

dixe

n, 2

004

1517

12

00

01

00

15

12

11

12

210

Fie

ld2

01

00

10

00

0

Kep

enek

and

Koy

uncu

, 200

221

240

20

10

10

00

43

32

23

31

17G

reen

hous

e3

01

10

00

01

0

Lam

bert

s et

al.,

198

913

150

00

10

00

00

13

22

11

21

12A

quac

ultu

re2

01

10

00

00

0

Lars

on e

t al.,

200

216

180

10

11

10

01

52

21

12

12

11F

ield

20

10

00

00

10

Rev

iew

Pub

licat

ions

AN

ZE

CC

, 199

20

00

00

00

00

00

00

00

00

00

0N

o st

udy

00

00

00

00

00

Cal

iforn

ia S

traw

berr

y C

omm

issi

on, 2

004

66

00

00

20

00

24

00

00

00

22

No

stud

y0

00

00

00

00

0

Dom

ato

et a

l., 2

000

55

00

00

10

00

12

00

00

00

33

No

stud

y0

00

00

00

00

0

Gra

ttan

, 199

12

30

00

00

10

00

10

00

00

01

1N

o st

udy

10

00

10

00

00

Man

itoba

Agr

icul

ture

, Foo

d an

d R

ural

Ini

tiativ

es, 2

001

11

00

00

10

00

01

00

00

00

00

No

stud

y0

00

00

00

00

0

Sch

rade

r an

d W

elch

, 199

02

40

00

01

10

00

20

00

00

00

0N

o st

udy

20

10

10

00

00

UC

Fru

it an

d N

ut R

esea

rch

and

Info

rmat

ion

Cen

ter,

199

94

40

00

12

00

01

40

00

00

00

0N

o st

udy

00

00

00

00

00

Vot

h an

d B

ringh

urst

, 196

74

50

11

01

00

01

40

00

00

00

0N

o st

udy

10

00

01

00

00

Wel

ch a

nd B

eute

l, 19

871

10

00

01

00

00

10

00

00

00

0N

o st

udy

00

00

00

00

00

Wic

hman

n, 2

004

00

00

00

00

00

00

00

00

00

00

No

stud

y0

00

00

00

00

0

Mon

day,

Mar

ch 2

1, 2

005

Page

3 o

f 4

Lit

erat

ure

Eva

luat

ion

(o

rgan

ized

alp

hab

etic

ally

)

SCORE (A + Q)

Nu

rser

y C

rop

s

Climate

Irrigationmethod

Soil type


Culturalpractices


Routes ofexposure

Rate ofexposure

Location

SCORE

ST

UD

Y A

PP

LIC

AB

ILIT

Y (

Max

imu

m S

core

= 2

7)

Experimentaldesign

Strength ofanalysis





study objectives

Level of review

SCORE

ST

UD

Y Q

UA

LIT

Y (

Max

imu

m S

core

= 2

1)

TOTAL SCORE

Typ

e o

f S

tud

y

Growth stage

Yield impact

Source of chloride



Osmotic effect


Fruit quality


SCORE

ST

UD

Y S

CO

PE

(M

axim

um

Sco

re =

9)

Exp

erim

enta

l Stu

dies

Ber

nste

in e

t al.,

197

228

342

11

31

02

12

132

11

32

33

15S

and

tank

and

fiel

d6

11

11

01

01

0

Fra

ncoi

s, 1

982

2832

21

13

11

21

214

21

12

23

314

Fie

ld4

11

10

00

01

0

Fra

ncoi

s an

d C

lark

, 197

829

322

11

31

12

12

142

11

32

33

15F

ield

30

11

00

00

10

Luni

n an

d S

tew

art,

1961

2225

11

11

11

21

110

21

11

13

312

Gre

enho

use

30

01

00

10

10

Lunt

et

al.,

195

732

352

12

31

21

22

163

11

32

33

16G

reen

hous

e3

01

10

00

01

0

Lunt

et

al.,

195

623

262

02

20

02

22

123

11

00

33

11G

reen

hous

e3

01

10

00

01

0

Mon

k an

d P

eter

son,

196

226

291

11

11

12

11

103

11

32

33

16F

ield

30

11

00

00

10

Mon

k an

d W

iebe

, 196

125

271

10

11

12

11

93

11

32

33

16F

ield

and

gre

enho

use

20

01

00

00

10

Tow

nsen

d, 1

980

3134

11

11

11

22

111

33

33

32

320

Gre

enho

use

30

11

00

00

10

Wu

et a

l., 1

995

3538

22

23

11

21

216

33

22

33

319

Gre

enho

use

30

01

10

00

10

Wu

et a

l. (b

), 2

001

3538

23

23

11

32

219

32

22

13

316

Fie

ld a

nd g

reen

hous

e3

01

10

00

01

0

Wu

et a

l. (S

loss

on),

200

028

302

30

31

03

32

171

11

21

32

11F

ield

20

01

00

00

10

Wu

et a

l. (S

loss

on),

199

932

362

32

31

23

22

202

11

21

32

12F

ield

and

gre

enho

use

41

11

00

00

10

Wu

et a

l. (S

loss

on),

199

819

212

00

30

10

12

91

11

11

32

10G

reen

hous

e2

01

10

00

00

0

Wu

et a

l. (S

loss

on)

(a),

200

135

382

32

31

23

22

203

22

22

22

15F

ield

30

11

00

00

10

Rev

iew

Pub

licat

ions

Bai

ley

et a

l., 1

999

1016

12

00

00

20

16

00

01

00

34

Ext

ensi

on p

ublic

atio

n6

11

11

01

01

0

Ber

nste

in, 1

964

1519

20

03

11

10

210

00

02

00

35

Ext

ensi

on-t

ype

leaf

let

40

11

10

00

10

Cab

rera

, 200

312

161

20

20

02

01

80

00

10

03

4E

xten

sion

pub

licat

ion

40

11

00

10

10

Car

man

, 200

314

143

02

00

00

03

80

00

30

03

6E

xten

sion

-typ

e re

view

00

00

00

00

00

Car

pent

er,

1970

69

10

01

00

10

14

00

00

00

22

Rev

iew

31

11

00

00

00

Dar

lingt

on, 2

004

2930

33

33

33

33

327

00

02

00

02

Per

sona

l com

mun

icat

ion

10

01

00

00

00

Far

nham

et a

l., 1

993

1924

23

03

02

30

215

00

01

00

34

Ext

ensi

on p

ublic

atio

n5

01

11

01

01

0

Gut

man

, 200

429

303

33

33

33

33

270

00

20

00

2P

erso

nal c

omm

unic

atio

n1

00

10

00

00

0

Maa

s, 1

990

1521

20

02

00

30

29

00

03

00

36

Rev

iew

61

11

10

10

10

Maa

s, 1

987

712

00

00

00

20

02

00

02

00

35

Rev

iew

pap

er5

01

11

01

01

0

Maa

s, 1

986

1521

20

03

00

20

29

00

03

00

36

Rev

iew

61

11

10

10

10

Rob

bins

and

Klin

gam

an,

2000

1114

10

20

22

00

18

00

00

00

33

Ext

ensi

on g

uida

nce

30

01

10

00

10

Ste

phen

s, 2

002

68

10

00

00

00

12

00

01

00

34

Ext

ensi

on p

ublic

atio

n2

00

11

00

00

0

Mon

day,

Mar

ch 2

1, 2

005

Page

4 o

f 4

Lit

erat

ure

Eva

luat

ion

(o

rgan

ized

by

des

cen

din

g s

core

)

SCORE (A + Q)

Avo

cad

os

Climate

Irrigationmethod

Soil type


Culturalpractices


Routes ofexposure

Rate ofexposure

Location

SCORE

ST

UD

Y A

PP

LIC

AB

ILIT

Y (

Max

imu

m S

core

= 2

7)

Experimentaldesign

Strength ofanalysis





study objectives

Level of review

SCORE

ST

UD

Y Q

UA

LIT

Y (

Max

imu

m S

core

= 2

1)

TOTAL SCORE

Typ

e o

f S

tud

y

Growth stage

Yield impact

Source of chloride



Osmotic effect


Fruit quality


SCORE

ST

UD

Y S

CO

PE

(M

axim

um

Sco

re =

9)

Exp

erim

enta

l Stu

dies

Mon

tgom

ery

Wat

son,

199

737

422

32

33

32

32

233

11

22

32

14F

ield

50

11

01

00

11

Mic

kelb

art

and

Arp

aia,

200

235

362

21

30

22

12

153

33

23

33

20S

and

cultu

re,

outd

oors

10

01

00

00

00

Bin

gham

et

al.,

196

828

363

00

20

02

33

132

21

13

33

15S

and

cultu

re8

11

11

11

11

0

Fab

er e

t al.,

199

532

352

23

32

32

32

222

11

11

31

10F

ield

30

11

00

00

10

Arp

aia

et a

l., 1

996

3032

22

23

23

33

222

11

10

23

08

Fie

ld2

01

10

00

00

0

Ost

er a

nd A

rpai

a, 2

002

2831

22

23

03

23

219

21

11

12

19

Fie

ld3

01

10

10

00

0

Haa

s (b

), 1

950

2830

20

03

00

23

212

22

33

23

116

Gre

enho

use

20

01

10

00

00

Bar

et a

l., 1

997

2630

20

12

00

33

011

12

32

22

315

San

d cu

lture

40

01

10

11

00

Ber

nste

in e

t al.,

200

427

281

00

10

02

11

63

33

33

33

21S

cree

nhou

se1

00

10

00

00

0

Wie

sman

, 199

525

281

01

10

02

11

72

33

23

23

18G

reen

hous

e3

00

11

00

10

0

Ehl

ig a

nd B

erns

tein

, 19

5925

262

00

20

11

32

112

12

22

23

14S

and

beds

10

01

00

00

00

Aye

rs,

1950

2326

20

01

00

22

29

12

22

33

114

Cul

ture

sol

utio

n3

00

11

01

00

0

Mei

ri et

al.,

199

925

251

11

10

12

21

103

22

23

21

15F

ield

00

00

00

00

00

Kad

man

, 196

324

251

00

10

02

31

83

22

13

23

16S

cree

nhou

se1

00

10

00

00

0

Ber

nste

in e

t al.,

200

123

251

00

00

02

10

42

33

32

33

19S

cree

nhou

se2

10

10

00

00

0

Dow

nton

, 197

823

252

00

10

12

30

91

12

22

33

14S

and

cultu

re,

gree

nhou

se2

00

10

00

10

0

Gon

zale

z-R

osas

et a

l., 2

003

2325

00

02

00

00

02

33

33

33

321

Lab

20

01

00

10

00

Kur

tz e

t al.,

199

222

251

20

10

32

01

103

21

12

21

12F

ield

30

11

00

00

10

Cro

wle

y et

al.,

199

923

241

11

10

02

31

102

22

22

21

13S

and

cultu

re,

gree

nhou

se1

00

10

00

00

0

Gus

tafs

on,

1962

2224

22

00

03

23

214

11

11

13

08

Fie

ld2

00

10

00

00

1

Bin

gham

and

Ric

hard

s, 1

958

2323

20

02

03

00

29

13

32

22

114

Fie

ld0

00

00

00

00

0

Cha

rtzo

ulak

is e

t al

., 2

002

2223

20

00

00

00

02

23

33

33

320

Con

tain

er1

00

00

01

00

0

Kad

man

and

Ben

-Ya'

acov

, 19

6921

231

00

30

02

21

91

12

22

31

12C

onta

iner

, out

door

s2

00

10

00

10

0

Pat

el e

t al.,

197

620

212

01

10

01

32

102

12

23

00

10C

onta

iner

, gre

enho

use

10

01

00

00

00

Laha

v et

al.,

199

220

201

11

30

32

21

141

11

11

01

6F

ield

00

00

00

00

00

Aye

rs e

t al.

(a),

195

119

202

00

12

00

02

71

12

22

31

12M

ensu

rativ

e la

b1

00

01

00

00

0

Gus

tafs

on e

t al.,

197

318

192

00

00

02

22

82

11

13

11

10F

ield

10

01

00

00

00

Haa

s an

d B

rusc

a, 1

955

1819

20

03

00

22

211

01

11

12

17

Gre

enho

use

10

01

00

00

00

Kad

man

, 196

818

191

00

20

02

31

91

11

11

31

9C

onta

iner

, out

door

s1

00

10

00

00

0

Em

blet

on e

t al.,

196

218

182

00

02

00

02

62

21

12

13

12F

ield

, men

sura

tive

00

00

00

00

00

Coo

per,

195

116

181

00

10

12

11

72

11

12

11

9C

onta

iner

, out

door

s2

00

10

00

00

1

Ost

er e

t al.,

198

815

172

00

30

01

00

61

11

11

31

9G

reen

hous

e2

00

11

00

00

0

Sal

azar

-Gar

cia

and

Cor

tes-

Flo

res,

198

815

161

11

10

02

01

70

11

21

21

8M

ensu

rativ

e1

00

00

00

00

1

Tues

day,

Apr

il 12

, 200

5Pa

ge 1

of 4

Lit

erat

ure

Eva

luat

ion

(o

rgan

ized

by

des

cen

din

g s

core

)

SCORE (A + Q)

Avo

cad

os

Climate

Irrigationmethod

Soil type


Culturalpractices


Routes ofexposure

Rate ofexposure

Location

SCORE

ST

UD

Y A

PP

LIC

AB

ILIT

Y (

Max

imu

m S

core

= 2

7)

Experimentaldesign

Strength ofanalysis





study objectives

Level of review

SCORE

ST

UD

Y Q

UA

LIT

Y (

Max

imu

m S

core

= 2

1)

TOTAL SCORE

Typ

e o

f S

tud

y

Growth stage

Yield impact

Source of chloride



Osmotic effect


Fruit quality


SCORE

ST

UD

Y S

CO

PE

(M

axim

um

Sco

re =

9)

Sal

azar

-Gar

cia

and

Larq

ué-S

aave

dra,

198

514

160

01

10

02

10

53

11

12

01

9G

reen

hous

e2

00

10

00

10

0

Haa

s (a

), 1

950

1515

20

02

00

00

26

01

22

03

19

San

d/so

il cu

lture

00

00

00

00

00

Haa

s (c

), 1

950

1515

20

03

00

00

27

11

11

12

18

Men

sura

tive

00

00

00

00

00

Haa

s, 1

936

1415

20

00

00

00

24

02

22

12

110

Men

sura

tive

10

00

00

00

10

Coo

per

and

Gor

ton,

195

014

141

00

10

00

01

30

13

33

10

11M

ensu

rativ

e0

00

00

00

00

0

Ben

-Ya'

acov

et a

l., 1

992

1114

00

00

00

23

05

20

00

03

16

Fie

ld a

nd n

urse

ry3

01

10

00

00

1

Rev

iew

Pub

licat

ions

Am

rhei

n, 1

999

2328

33

03

32

23

221

00

11

00

02

Rev

iew

of o

ne s

tudy

50

11

10

10

10

Fab

er, 2

004

1922

33

00

03

23

216

00

00

00

33

No

stud

y3

00

10

10

00

1

Sha

lhev

et, 1

999

1620

03

03

03

33

015

00

00

00

11

No

stud

y4

01

10

10

10

0

Par

tida,

200

215

172

00

23

22

22

150

00

00

00

0F

ield

stu

dies

rev

iew

20

10

01

00

00

Sha

lhev

et, 1

994

1417

12

01

13

23

114

00

00

00

00

Rev

iew

of s

tudi

es3

10

11

00

00

0

Laha

v an

d A

ycic

egi-L

owen

gart

, 200

316

161

30

10

32

01

110

02

20

01

5R

evie

w o

f stu

dies

00

00

00

00

00

Tra

sk, 1

960

1314

31

10

03

11

313

00

00

00

00

Per

sona

l exp

erie

nce

10

01

00

00

00

Gra

ttan

and

Ost

er,

2002

1114

20

01

02

02

29

00

00

00

22

No

stud

y3

00

11

01

00

0

Ost

er, 2

002

914

20

01

00

00

25

00

21

00

14

Rev

iew

of s

tudi

es5

01

11

11

00

0

Aye

rs a

nd W

estc

ot,

1985

912

00

03

03

00

06

00

00

00

33

No

stud

y3

00

11

01

00

0

Gre

enw

ay a

nd M

unns

, 19

809

120

00

00

00

00

00

22

20

03

9N

o st

udy

30

00

10

11

00

Maa

s, 1

990

811

00

03

00

00

03

00

20

00

35

No

stud

y3

00

11

01

00

0

Coo

per

et a

l., 1

952

1010

00

00

00

00

00

22

11

21

110

Rev

iew

00

00

00

00

00

Tho

mas

, 193

29

103

00

00

30

03

90

00

00

00

0P

erso

nal e

xper

ienc

e1

00

10

00

00

0

Ber

gh, 1

967

99

30

00

30

00

39

00

00

00

00

No

stud

y0

00

00

00

00

0

Gus

tafs

on,

1976

66

03

00

03

00

06

00

00

00

00

No

stud

y0

00

00

00

00

0

Haa

s, 1

928

66

20

00

02

00

26

00

00

00

00

No

stud

y0

00

00

00

00

0

Gaz

it an

d K

adm

an, 1

976

56

00

00

00

00

00

00

22

00

15

No

stud

y1

00

10

00

00

0

Ben

-Ya'

acov

, 197

62

20

00

00

00

00

00

01

10

00

2N

o st

udy

00

00

00

00

00

Tues

day,

Apr

il 12

, 200

5Pa

ge 2

of 4

Lit

erat

ure

Eva

luat

ion

(o

rgan

ized

by

des

cen

din

g s

core

)

SCORE (A + Q)

Str

awb

erri

es

Climate

Irrigationmethod

Soil type


Culturalpractices


Routes ofexposure

Rate ofexposure

Location

SCORE

ST

UD

Y A

PP

LIC

AB

ILIT

Y (

Max

imu

m S

core

= 2

7)

Experimentaldesign

Strength ofanalysis





study objectives

Level of review

SCORE

ST

UD

Y Q

UA

LIT

Y (

Max

imu

m S

core

= 2

1)

TOTAL SCORE

Typ

e o

f S

tud

y

Growth stage

Yield impact

Source of chloride



Osmotic effect


Fruit quality


SCORE

ST

UD

Y S

CO

PE

(M

axim

um

Sco

re =

9)

Exp

erim

enta

l Stu

dies

Kep

enek

and

Koy

uncu

, 200

221

240

20

10

10

00

43

32

23

31

17G

reen

hous

e3

01

10

00

01

0

Giu

ffrid

a et

al.,

200

120

241

00

10

10

11

52

32

22

31

15A

rtifi

cial

med

ia/a

quac

ultu

re4

01

10

10

01

0

Ehl

ig, 1

961

2223

01

01

01

13

07

31

12

32

315

Aqu

acul

ture

10

01

00

00

00

Ehl

ig a

nd B

erns

tein

, P

art B

, 19

5820

230

01

11

00

10

43

21

22

33

16F

ield

30

11

00

00

10

Ehl

ig a

nd B

erns

tein

, P

art A

, 19

5818

220

00

10

10

10

32

21

22

33

15F

ield

and

san

d cu

lture

40

01

11

10

00

Lars

on e

t al.,

200

216

180

10

11

10

01

52

21

12

12

11F

ield

20

10

00

00

10

Han

sen

and

Ben

dixe

n, 2

004

1517

12

00

01

00

15

12

11

12

210

Fie

ld2

01

00

10

00

0

Lam

bert

s et

al.,

198

913

150

00

10

00

00

13

22

11

21

12A

quac

ultu

re2

01

10

00

00

0

Bro

wn

and

Vot

h, 1

955

1314

01

11

00

00

14

01

11

13

29

Fie

ld1

01

00

00

00

0

Rev

iew

Pub

licat

ions

Cal

iforn

ia S

traw

berr

y C

omm

issi

on, 2

004

66

00

00

20

00

24

00

00

00

22

No

stud

y0

00

00

00

00

0

Dom

ato

et a

l., 2

000

55

00

00

10

00

12

00

00

00

33

No

stud

y0

00

00

00

00

0

Vot

h an

d B

ringh

urst

, 196

74

50

11

01

00

01

40

00

00

00

0N

o st

udy

10

00

01

00

00

UC

Fru

it an

d N

ut R

esea

rch

and

Info

rmat

ion

Cen

ter,

199

94

40

00

12

00

01

40

00

00

00

0N

o st

udy

00

00

00

00

00

Sch

rade

r an

d W

elch

, 199

02

40

00

01

10

00

20

00

00

00

0N

o st

udy

20

10

10

00

00

Gra

ttan

, 199

12

30

00

00

10

00

10

00

00

01

1N

o st

udy

10

00

10

00

00

Man

itoba

Agr

icul

ture

, Foo

d an

d R

ural

Ini

tiativ

es, 2

001

11

00

00

10

00

01

00

00

00

00

No

stud

y0

00

00

00

00

0

Wel

ch a

nd B

eute

l, 19

871

10

00

01

00

00

10

00

00

00

0N

o st

udy

00

00

00

00

00

AN

ZE

CC

, 199

20

00

00

00

00

00

00

00

00

00

0N

o st

udy

00

00

00

00

00

Wic

hman

n, 2

004

00

00

00

00

00

00

00

00

00

00

No

stud

y0

00

00

00

00

0

Tues

day,

Apr

il 12

, 200

5Pa

ge 3

of 4

Lit

erat

ure

Eva

luat

ion

(o

rgan

ized

by

des

cen

din

g s

core

)

SCORE (A + Q)

Nu

rser

y C

rop

s

Climate

Irrigationmethod

Soil type


Culturalpractices


Routes ofexposure

Rate ofexposure

Location

SCORE

ST

UD

Y A

PP

LIC

AB

ILIT

Y (

Max

imu

m S

core

= 2

7)

Experimentaldesign

Strength ofanalysis





study objectives

Level of review

SCORE

ST

UD

Y Q

UA

LIT

Y (

Max

imu

m S

core

= 2

1)

TOTAL SCORE

Typ

e o

f S

tud

y

Growth stage

Yield impact

Source of chloride



Osmotic effect


Fruit quality


SCORE

ST

UD

Y S

CO

PE

(M

axim

um

Sco

re =

9)

Exp

erim

enta

l Stu

dies

Wu

et a

l., 1

995

3538

22

23

11

21

216

33

22

33

319

Gre

enho

use

30

01

10

00

10

Wu

et a

l. (b

), 2

001

3538

23

23

11

32

219

32

22

13

316

Fie

ld a

nd g

reen

hous

e3

01

10

00

01

0

Wu

et a

l. (S

loss

on)

(a),

200

135

382

32

31

23

22

203

22

22

22

15F

ield

30

11

00

00

10

Wu

et a

l. (S

loss

on),

199

932

362

32

31

23

22

202

11

21

32

12F

ield

and

gre

enho

use

41

11

00

00

10

Lunt

et

al.,

195

732

352

12

31

21

22

163

11

32

33

16G

reen

hous

e3

01

10

00

01

0

Tow

nsen

d, 1

980

3134

11

11

11

22

111

33

33

32

320

Gre

enho

use

30

11

00

00

10

Ber

nste

in e

t al.,

197

228

342

11

31

02

12

132

11

32

33

15S

and

tank

and

fiel

d6

11

11

01

01

0

Fra

ncoi

s an

d C

lark

, 197

829

322

11

31

12

12

142

11

32

33

15F

ield

30

11

00

00

10

Fra

ncoi

s, 1

982

2832

21

13

11

21

214

21

12

23

314

Fie

ld4

11

10

00

01

0

Wu

et a

l. (S

loss

on),

200

028

302

30

31

03

32

171

11

21

32

11F

ield

20

01

00

00

10

Mon

k an

d P

eter

son,

196

226

291

11

11

12

11

103

11

32

33

16F

ield

30

11

00

00

10

Mon

k an

d W

iebe

, 196

125

271

10

11

12

11

93

11

32

33

16F

ield

and

gre

enho

use

20

01

00

00

10

Lunt

et

al.,

195

623

262

02

20

02

22

123

11

00

33

11G

reen

hous

e3

01

10

00

01

0

Luni

n an

d S

tew

art,

1961

2225

11

11

11

21

110

21

11

13

312

Gre

enho

use

30

01

00

10

10

Wu

et a

l. (S

loss

on),

199

819

212

00

30

10

12

91

11

11

32

10G

reen

hous

e2

01

10

00

00

0

Rev

iew

Pub

licat

ions

Dar

lingt

on, 2

004

2930

33

33

33

33

327

00

02

00

02

Per

sona

l com

mun

icat

ion

10

01

00

00

00

Gut

man

, 200

429

303

33

33

33

33

270

00

20

00

2P

erso

nal c

omm

unic

atio

n1

00

10

00

00

0

Far

nham

et a

l., 1

993

1924

23

03

02

30

215

00

01

00

34

Ext

ensi

on p

ublic

atio

n5

01

11

01

01

0

Maa

s, 1

990

1521

20

02

00

30

29

00

03

00

36

Rev

iew

61

11

10

10

10

Maa

s, 1

986

1521

20

03

00

20

29

00

03

00

36

Rev

iew

61

11

10

10

10

Ber

nste

in, 1

964

1519

20

03

11

10

210

00

02

00

35

Ext

ensi

on-t

ype

leaf

let

40

11

10

00

10

Cab

rera

, 200

312

161

20

20

02

01

80

00

10

03

4E

xten

sion

pub

licat

ion

40

11

00

10

10

Bai

ley

et a

l., 1

999

1016

12

00

00

20

16

00

01

00

34

Ext

ensi

on p

ublic

atio

n6

11

11

01

01

0

Car

man

, 200

314

143

02

00

00

03

80

00

30

03

6E

xten

sion

-typ

e re

view

00

00

00

00

00

Rob

bins

and

Klin

gam

an,

2000

1114

10

20

22

00

18

00

00

00

33

Ext

ensi

on g

uida

nce

30

01

10

00

10

Maa

s, 1

987

712

00

00

00

20

02

00

02

00

35

Rev

iew

pap

er5

01

11

01

01

0

Car

pent

er,

1970

69

10

01

00

10

14

00

00

00

22

Rev

iew

31

11

00

00

00

Ste

phen

s, 2

002

68

10

00

00

00

12

00

01

00

34

Ext

ensi

on p

ublic

atio

n2

00

11

00

00

0

Tues

day,

Apr

il 12

, 200

5Pa

ge 4

of 4

Appendix C Nursery Crop Evaluation Scores

RD

D/0

5077

0013

(C

LR28

34.D

OC

) C

-1

AP

PE

ND

IX C

Nu

rser

y C

rop

Eva

luat

ion

Sco

res

TA

BL

E C

-1

Sum

mar

y of

Chl

orid

e T

hres

hold

s S

ugge

sted

by

Exp

erim

enta

l Dat

a an

d O

vera

ll E

valu

atio

n S

core

N

urse

ry C

rop

Eva

luat

ion

Sco

res

So

urc

e

Sc

op

e

Ap

pli

ca

bil

ity

Qu

ali

ty

To

tal

Sc

ore

Th

res

ho

ld T

yp

e

Va

lue

C

om

me

nts

Wu e

t al., 2001a

3

20

15

38

Irrigation w

ate

r (C

lw)

>300 m

g/L

N

o o

bserv

able

eff

ects

at

300 m

g/L

with d

rip

irrigation.

Wu e

t al., 2001b

3

19

16

38

Irrigation w

ate

r (C

lw)

>300 m

g/L

S

am

e e

xperim

enta

l data

as W

u e

t al., 2001a.

No

observ

able

eff

ects

at

300 m

g/L

with d

rip irr

igation.

Wu e

t al., 1995

3

16

19

38

Irrigation w

ate

r (C

lw)

<1,4

84 m

g/L

Ir

rigation w

ate

r desig

ned to m

imic

regenera

nt

waste

wate

r fr

om

KC

l-based w

ate

r softeners

. S

prinkle

r irrigation o

f a s

ingle

solu

tion. S

om

e p

lants

to

lera

ted s

olu

tion w

ell,

oth

ers

did

not.

Wu e

t al., 1999

4

20

12

36

Irrigation w

ate

r (C

lw)

<300 m

g/L

T

hre

shold

som

e v

alu

e less than 3

00 m

g/L

for

sprinkle

r irrigation w

ith s

ensitiv

e s

pecie

s.

Lunt

et al.,

1957

3

16

16

35

Irrigation w

ate

r (C

lw)

<1,4

18 m

g/L

A

pplie

d a

s N

aC

l and C

aC

l 2.

Bern

ste

in e

t al.,

1972

6

13

15

34

Soil

EC

e

2.5

to 3

.0 d

S/m

A

dvers

e e

ffects

in m

ost sensitiv

e s

pecie

s e

xam

ined.

Fra

ncois

and C

lark

, 1978

3

14

15

32

Soil

EC

e

2.6

dS

/m

Accepta

ble

reduction in g

row

th f

or

most sensitiv

e

pla

nts

.

Fra

ncois

, 1982

4

14

14

32

Soil

EC

e

<4.0

dS

/m

Thre

shold

for

folia

r in

jury

in s

ensitiv

e p

lants

.

Wu e

t al., 2000

2

17

11

30

Irrigation w

ate

r (C

lw)

>160 m

g/L

N

o s

alt s

tress a

t 160 m

g/L

with s

prinkle

r irrigation.

Monk a

nd P

ete

rson,

1962

3

10

16

29

Irrigation w

ate

r (C

lw)

<2,5

00 m

g/L

Monk a

nd W

eib

e,

1961

2

9

16

27

Irrigation w

ate

r (C

lw)

<2,2

27 t

o

2,5

52 m

g/L

O

nly

hig

h-s

alin

ity s

olu

tions teste

d.

Lunt

et al.,

1956

3

12

11

26

Irrigation w

ate

r (C

lw)

<886 m

g/L

S

light

leaf

dro

p a

nd leaf-

tip b

urn

, no c

hlo

rosis

, avera

ge g

row

th.

Lunin

and S

tew

art

, 1961

3

10

12

25

Soil

EC

e

3 d

S/m

A

dvers

e e

ffects

in t

he m

ost sensitiv

e s

pecie

s

exam

ined.

Note

s:

CaC

l 2

=

calc

ium

chlo

ride

Clw

=

irrigation w

ate

r chlo

ride

KC

l =

pota

ssiu

m c

hlo

ride

NaC

l

=

sodiu

m c

hlo

ride

RD

D/0

5077

0013

(C

LR28

34.D

OC

) C

-2

TA

BL

E C

-2

Sum

mar

y of

Chl

orid

e T

hres

hold

s S

ugge

sted

by

Ext

ensi

on-t

ype

Do

cum

ents

and

Ove

rall

Eva

luat

ion

Sco

re

Nur

sery

Cro

p E

valu

atio

n S

core

s

So

urc

e

Sc

op

e

Ap

pli

ca

bil

ity

Qu

ali

ty

To

tal

Sc

ore

Th

res

ho

ld T

yp

e

Va

lue

C

om

me

nts

Fa

rnh

am

et a

l.,

198

5

5

15

4

2

4

Irri

ga

tio

n w

ate

r >

70

mg

/L

Su

rfa

ce

irr

iga

tio

n, th

resh

old

for

“in

cre

asin

g

de

gre

e o

f p

rob

lem

.”

Fa

rnh

am

et a

l.,

198

5

Irri

ga

tio

n w

ate

r >

10

0 m

g/L

S

pri

nkle

r ir

rig

ation

. G

ive

n in

tab

le a

s

3.0

me

q/L

or

10

0 m

g/L

, a

lth

oug

h 3

.0 m

eq

/L

= 1

07

mg

/L.

Th

resh

old

fo

r “in

cre

asin

g

de

gre

e o

f p

rob

lem

.”

Be

rnste

in, 1

964

4

1

0

5

19

S

oil

EC

e

3 d

S/m

T

hre

sh

old

fo

r d

am

ag

e w

ith

sh

rub

s

esta

blis

hed

in

a la

ndscap

e s

ettin

g.

Ba

iley e

t a

l., 1

999

6

6

4

1

6

Irri

ga

tio

n w

ate

r 7

1 m

g/L

U

pp

er

limit f

or

gre

en

ho

use

use

.

Ca

bre

ra, 1

99

8

4

8

4

16

Ir

rig

atio

n w

ate

r 1

00

mg

/L

Ca

refu

lly c

onsid

er

use

of

wa

ter

with

>

10

0 m

g/L

Cl.

Ro

bb

ins a

nd

Klin

gam

an

, 2

00

0

3

8

3

14

Ir

rig

atio

n w

ate

r <

50

or

<1

40

<

50

is o

ptim

um

; 1

40 is u

pp

er

limit.

Ste

ph

en

s, 2

002

2

2

4

8

Ir

rig

atio

n w

ate

r <

70

to 9

0

mg

/LM

ost

situ

atio

ns.

Ste

ph

en

s, 2

002

Ir

rig

atio

n w

ate

r >

20

0 m

g/L

L

ea

f-tip

an

d –

ma

rgin

bu

rns w

ith

lo

w

lea

ch

ing

fra

ctio

ns; a

lso

no

t su

ita

ble

fo

r tr

ickle

or

su

bir

rig

atio

n. C

on

trolle

d lea

chin

g

mig

ht

alle

via

te p

rob

lem

s n

ea

r 2

00

mg

/L.

No

tes:

dS

/m

=

de

cis

iem

en

s p

er

me

ter

Cl

=

ch

lorid

e

EC

e

=

so

il e

xtr

act

ele

ctr

ical co

ndu

ctivity

me

q/L

=

m

illie

qu

iva

len

ts p

er

lite

r

mg

/L

=

mill

igra

ms p

er

lite

r

APPENDIX C NURSERY CROP EVALUATION SCORES

RDD/050770013 (CLR2834.DOC) C-3

Works Cited

Bailey, D., T. Bilderback, and D. Bir. 1999. Water Considerations for Container Production of Plants. North Carolina State University, Horticulture Information Leaflet #557.

Bernstein, L. 1964. “Reducing Salt Injury to Ornamental Shrubs in the West.” U.S. Department of Agriculture Home and Garden Bulletin. 95:6.

Bernstein, L., L. E. Francois, and R. A. Clark. 1972. “Salt Tolerance of Ornamental Shrubs and Ground Covers.” Journal of American Society for Horticultural Science. 97:550-566.

Cabrera, I. 1998. Evaluating Water Quality for Ornamental Plant Production. Rutgers Cooperative Extension Fact Sheet FS893.

Farnham, D. S., R. F. Hasek, and J. L. Paul. 1985. Water Quality: Its Effects on Ornamental Plants. University of California Cooperative Extension Leaflet #2995.

Francois, L. E. 1982. “Salt Tolerance of Eight Ornamental Tree Species.” Journal of American Society for Horticultural Science. 107:66-68.

Francois, L. E. and R. A. Clark. 1978. “Salt Tolerance of Ornamental Shrubs, Trees, and Iceplant.” Journal of American Society for Horticultural Science. 103:280-283.

Lunin, J. and F. B. Stewart. 1961. “The Effect of Soil Salinity on Azaleas and Camellias.” Proceedings on Journal of American Society for Horticultural Science. 77:528-532.

Lunt, O. R., H. C. Kohl, Jr., and A. M. Kofranek. 1957. “Tolerance of Azaleas and Gardenias to Salinity Condition and Boron.” Proceedings on Journal of American Society for Horticultural Science. 69:543-548.

Lunt, O. R., H. C. Kohl, and A. M. Kofranek. 1956. “The Effect of Bicarbonate and Other Constituents of Irrigation Water on the Growth of Azaleas.” Proceedings on Journal of American Society for Horticultural Science. 68:537-544.

Monk, R. and H. B. Peterson. 1962. “Tolerance of Some Trees and Shrubs to Saline Conditions.” Proceedings on Journal of American Society on Horticultural Science. 81:556-561.

Monk, R. and H. H. Weibe. 1961. “Salt Tolerance and Protoplasmic Salt Hardiness of Various Woody and Herbaceous Ornamental Plants.” Plant Physiology. 36:478-482.

Robbins, J. and G. Klingaman. 2000. “Irrigation Water for Greenhouses and Nurseries.” University of Arkansas, Division of Agriculture, Cooperative Extension Service.

Stephens, R. 2002. Water Quality and Nursery Crop Nutrition. The Nursery Papers Issue No. 2002/11, Nursery & Garden Industry Australia and Horticulture Australia.

Wu, L. X. Guo, K. Hunter, E. Zagory, R. Waters, and J. Brown. 2001a. “Studies of Salt Tolerance of Landscape Plant Species and California Native Grasses for Recycled Water Irrigation.” University of California-Davis, Slosson Research Endowment for Ornamental Horticulture Research Report 2000-2001.

APPENDIX C NURSERY CROP EVALUATION SCORES

C-4 DD/050770013 (CLR2834.DOC)

Wu, L., X. Guo, and A. Harivandi. 2001b. “Salt Tolerance and Salt Accumulation of Landscape Plants Irrigated by Sprinkler and Drip Irrigation Systems.” Journal of Plant Nutrition. 24(9):1473-1490.

Wu, L., X. Guo, and J. Brown. 2000. “Studies of Recycled Water Irrigation and Performance of Landscape Plants under Urban Landscape Conditions.” University of California-Davis, Slosson Research Endowment for Ornamental Horticulture Research Report 1999-2000.

Wu, L., X. Guo, A. Harivandi, R. Waters, and J. Brown. 1999. “Study of California Native Grass and Landscape Plant Species for Recycled Water Irrigation in California Landscapes and Gardens.” University of California-Davis, Slosson Research Endowment for Ornamental Horticulture Research Report 1998-1999.

Wu, L., J. A. Harding, and M. A. Harivandi. 1998. “Studies of Recycled Water Irrigation and Effects of Elevated Mineral Nutrient Concentrations on Growth and Ion Uptake of Landscape Plant Species and Ornamental Grasses.” University of California-Davis, Slosson Research Endowment for Ornamental Horticulture Research Report 1995-1998.

Wu, L., J. Chen, H. Lin, P. Van Mantgem, M. A. Harivandi, and J. A. Harding. 1995. “Effects of Regenerant Wastewater Irrigation on Growth and Ion Uptake of Landscape Plants.” Journal of Environmental Horticulture. 13(2):92-96.

Appendix D Bibliography Table

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Avo

ca

do

Am

rhe

in,

C.

19

99

Re

vie

w o

f th

e r

ep

ort

title

d,

"City o

f E

sco

nd

ido

, A

vo

ca

do

Pilo

t P

roje

ct

Fin

al R

ep

ort

, A

n E

va

lua

tio

n o

f R

ecla

ime

d

Wa

ter

for

Use

on

Avo

ca

do

s,

Fiv

e Y

ea

r S

tud

y R

ep

ort

,"

pu

blis

he

d F

eb

rua

ry 1

99

7

De

pa

rtm

en

t o

f E

nviro

nm

en

tal S

cie

nce

s,

Un

ive

rsity o

f C

alif

orn

ia,

Riv

ers

ide

Avo

ca

do

Arp

aia

, M

.L.

No

ne

Se

ttin

g s

alin

ity a

nd

ch

lorid

e T

MD

LS

, S

an

ta C

lara

Riv

er,

Str

aw

be

rry a

nd

Avo

ca

do

Pre

se

nta

tio

n

Avo

ca

do

Arp

aia

, M

.L.,

Witn

ey,

G.W

., B

en

de

r, G

.S.,

Sto

ttle

mye

r, D

.S.,

Me

ye

r, J

.L.

19

96

Irrig

atio

n a

nd

Fe

rtili

za

tio

n M

an

ag

em

en

t o

f A

vo

ca

do

19

96

Avo

ca

do

Re

se

arc

h S

ym

po

siu

m C

alif

orn

ia A

vo

ca

do

So

cie

ty

an

d U

niv

ers

ity o

f C

alif

orn

ia,

Riv

ers

ide

p 1

3-1

6

Avo

ca

do

Arp

aia

, M

.L.,

Witn

ey,

G.W

., B

en

de

r, G

.S.,

Sto

ttle

mye

r, D

.S.,

Me

ye

r, J

.L.

19

95

Irrig

atio

n a

nd

Fe

rtili

za

tio

n M

an

ag

em

en

t o

f A

vo

ca

do

19

95

Ca

lifo

rnia

Avo

ca

do

Re

se

arc

h S

ym

po

siu

m C

alif

orn

ia

Avo

ca

do

So

cie

ty a

nd

Un

ive

rsity o

f C

alif

orn

ia,

Riv

ers

ide

p.

33

-37

Avo

ca

do

Aye

rs,

A.D

.1

95

0S

alt T

ole

ran

ce

of

Avo

ca

do

Tre

es G

row

n in

Cu

ltu

re

So

lutio

ns

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 3

4:

13

9-1

48

Avo

ca

do

Aye

rs,

A.D

., A

ldrich

, D

.G.,

Co

on

y,

J.J

.1

95

1b

Le

af

Bu

rn o

f A

vo

ca

do

Avo

ca

do

Aye

rs,

A.D

., A

ldrich

, D

.G.,

Co

on

y,

J.J

.1

95

1a

So

diu

m a

nd

Ch

lorid

e I

nju

ry o

f F

ue

rte

Avo

ca

do

Le

ave

sC

alif

orn

ia A

vo

ca

do

So

cie

ty Y

ea

rbo

ok 3

6:

17

4-1

78

Avo

ca

do

Ba

r, Y

, A

pe

lba

um

, A

., K

afk

afi,

U.,

Go

ren

, R

.1

99

7R

ela

tio

nsh

ip B

etw

ee

n C

hlo

rid

e a

nd

Nitra

te a

nd

Its

Eff

ect

on

Gro

wth

an

d M

ine

ral C

om

po

sitio

n o

f A

vo

ca

do

an

d C

itru

s P

lan

ts

Jo

urn

al o

f P

lan

t N

utr

itio

n,

20

(6):

71

5-7

31

Avo

ca

do

Ba

r, Y

., L

ah

av,

E.,

Ka

lma

r, D

.1

98

7S

ea

so

na

l C

ha

ng

es in

Nitro

ge

n C

on

ce

ntr

atio

n in

Avo

ca

do

Le

ave

s A

sso

cia

ted

with

Le

af

Ag

e a

nd

Fe

rtili

sa

tio

n R

eg

ime

So

uth

Afr

ica

n A

vo

ca

do

Gro

we

rs' A

sso

cia

tio

n Y

ea

rbo

ok 1

0:5

7-5

8

Pro

ce

ed

ing

s o

f th

e F

irst

Wo

rld

Avo

ca

do

Co

ng

ress

Avo

ca

do

Ba

r, Y

., K

afk

afi,

U.,

La

ha

v,

E.

19

92

Re

du

cin

g C

hlo

rid

e T

oxic

ity in

Avo

ca

do

by N

itra

teP

roce

ed

ing

s o

f S

eco

nd

Wo

rld

Avo

ca

do

Co

ng

ress p

37

3

Avo

ca

do

Ba

r, Y

., K

afk

afi,

U.,

La

ha

v,

E.

19

87

Nitra

te N

utr

itio

n a

s a

To

ol to

Re

du

ce

Ch

lorid

e T

oxic

ity

in A

vo

ca

do

So

uth

Afr

ica

n A

vo

ca

do

Gro

we

rs' A

sso

cia

tio

n Y

ea

rbo

ok 1

0:4

7-4

8.

Pro

ce

ed

ing

s o

f th

e F

irst

Wo

rld

Avo

ca

do

Co

ng

ress

Avo

ca

do

Be

nd

er,

G.

19

96

Dra

ft R

esu

lts o

f a

Fiv

e Y

ea

r S

tud

y U

sin

g R

ecla

ime

d

Wa

ter

in E

sco

nd

ido

, C

A

Mo

ntg

om

ery

Wa

tso

n

Avo

ca

do

Be

n-Y

a'a

co

v,

A.

19

76

Avo

ca

do

Ro

ots

tocks in

Use

in

Isra

el

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 5

9:6

6-6

8

Avo

ca

do

Be

n-Y

a'a

co

v,

A.,

Mic

he

lso

n,

E,

Zilb

ers

tain

e,

M.,

Ba

rka

n,

Z.,

Se

la,

I.

19

92

Se

lectio

n o

f C

lon

al A

vo

ca

do

Ro

ots

tocks in

Isra

el fo

r

Hig

h P

rod

uctivity u

nd

er

Diffe

ren

t S

oil

Co

nd

itio

ns

Pro

ce

ed

ing

s o

f S

eco

nd

Wo

rld

Avo

ca

do

Co

ng

ress p

52

1-5

26

Avo

ca

do

Be

rgh

, B

.O.

19

67

Re

aso

ns f

or

Lo

w Y

ield

s o

f A

vo

ca

do

sC

alif

orn

ia A

vo

ca

do

So

cie

ty Y

ea

rbo

ok 5

1:

16

1-1

72

Avo

ca

do

Be

rnste

in,

N.,

Io

ffe

, M

., Z

ilbe

rsta

ine

, M

.2

00

1S

alt-s

tre

ss e

ffe

cts

on

avo

ca

do

ro

ots

tock g

row

th.

I.

Esta

blis

hin

g c

rite

ria

fo

r d

ete

rmin

atio

n o

f sh

oo

t g

row

th

se

nsitiv

ity t

o t

he

str

ess

Pla

nt

an

d S

oil

23

3:

1-1

1

Avo

ca

do

Be

rnste

in,

N.,

Me

iri, A

, Z

ilbe

rsta

ine

M.

20

04

Ro

ot

Gro

wth

of

Avo

ca

do

Is M

ore

Se

nsitiv

e t

o S

alin

ity

tha

n S

ho

ot

Gro

wth

Jo

urn

al o

f th

e A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

12

9 (

2):

18

8-1

92

, M

arc

h

Avo

ca

do

Bin

gh

am

, F

.T.,

Fe

nn

, L

.B.

19

66

Ch

lorid

e I

nju

ry t

o H

aa

s A

vo

ca

do

Tre

es:

A S

an

dcu

ltu

re

Exp

erim

en

t

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 5

0:

99

-10

6

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

1 of

12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Avo

ca

do

Bin

gh

am

, F

.T.,

Fe

nn

, L

.B.,

an

d O

be

rtli,

J.J

.1

96

8A

Sa

nd

cu

ltu

re S

tud

y o

f C

hlo

rid

e T

oxic

ity t

o M

atu

re

Avo

ca

do

Tre

es

Pro

ce

ed

ing

s o

f th

e S

oil

Scie

nce

So

cie

ty o

f A

me

rica

, V

ol. 3

2

Avo

ca

do

Bin

gh

am

, F

.T.,

Ne

lso

n,

C.O

.1

97

1T

he

Eff

ects

of

So

diu

m o

n M

atu

re A

vo

ca

do

Tre

es

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 5

4:

75

-78

Avo

ca

do

Bin

gh

am

, F

.T.,

Ric

ha

rds,

S.J

.1

95

8E

ffe

cts

of

Irrig

atio

n T

rea

tme

nts

an

d R

ate

s o

f N

itro

ge

n

Fe

rtili

za

tio

n o

n Y

ou

ng

Ha

ss A

vo

ca

do

Tre

es.

III.

Ch

an

ge

s in

So

il C

he

mic

al P

rop

ert

ies

Pro

ce

ed

ing

s o

f th

e A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

71

:

30

4-3

09

Avo

ca

do

Bo

rst,

G.

19

73

Incid

en

ce

of

Avo

ca

do

Ro

ot

Ro

t in

Re

latio

n t

o

Exch

an

ge

ab

le S

oil

So

diu

m in

th

e V

icin

ity o

f F

allb

roo

k

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 5

6:

14

3-1

45

Avo

ca

do

Britt

o,

D.,

Ru

th,

T.,

La

p,

S.,

Kro

nzu

cke

r, H

.2

00

4C

ellu

lar

an

d W

ho

le-p

lan

t C

hlo

rid

e D

yn

am

ics in

Ba

rle

y:

Insig

hts

in

to C

hlo

rid

e –

Nitro

ge

n I

nte

ractio

ns a

nd

Sa

linity R

esp

on

se

s

Pla

nta

21

8:

61

5-6

22

.

Avo

ca

do

Ch

art

zo

ula

kis

, K

., P

ata

ka

s,

A.,

Ko

fid

i, G

.,

Bo

sa

ba

lidis

, A

., N

asto

u,

A.

20

02

Wa

ter

Str

ess A

ffe

cts

Le

af

An

ato

my,

Ga

s E

xch

an

ge

,

Wa

ter

Re

latio

ns a

nd

Gro

wth

of

Tw

o A

vo

ca

do

Cu

ltiv

ars

Scie

ntia

Ho

rtic

ultu

rae

95

: 3

9-5

0

Avo

ca

do

Ch

ira

ch

int,

W.

an

d T

urn

er,

D.W

.1

98

8S

ha

de

Re

du

ce

s t

he

Fo

liar

Sym

pto

ms o

f 'F

ue

rte

'

Avo

ca

do

Aff

ecte

d b

y S

alt,

with

ou

t S

ign

ific

an

tly

Ch

an

gin

g t

he

Co

nce

ntr

atio

n o

f N

a,

K o

r C

l in

th

e

Le

ave

s

Scie

ntia

Ho

rtic

ultu

rae

, 3

6:1

-15

Avo

ca

do

Co

ffe

y,

M.D

. a

nd

Gu

ille

me

t, F

.1

98

7A

vo

ca

do

Ro

ots

tocks

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 7

1:1

73

-17

9

Avo

ca

do

Co

op

er,

W.,

Co

wle

y,

W.,

an

d S

hu

ll, A

. 1

95

2S

ele

ctio

n f

or

Sa

lt T

ole

ran

ce

of

So

me

Su

btr

op

ica

l F

ruit

Pla

nts

Te

xa

s A

vo

ca

do

So

cie

ty 1

95

2 Y

ea

rbo

ok

Avo

ca

do

Co

op

er,

W.

19

51

Sa

lt T

ole

ran

ce

of

Avo

ca

do

s o

n V

ario

us R

oo

tsto

cks

Te

xa

s A

vo

ca

do

So

cie

ty 1

95

1 Y

ea

rbo

ok

Avo

ca

do

Co

op

er,

W.,

Go

rto

n,

B.

19

50

Re

latio

n o

f L

ea

f C

om

po

sitio

n t

o L

ea

f B

urn

of

Avo

ca

do

s

an

d O

the

r S

ub

-tro

pic

al F

ruits

Te

xa

s A

vo

ca

do

So

cie

ty 1

95

0 Y

ea

rbo

ok

Avo

ca

do

Cro

wle

y,

D.,

Arp

aia

, M

.L2

00

0R

oo

tsto

ck S

ele

ctio

ns f

or

Imp

rove

d S

alin

ity T

ole

ran

ce

of

Avo

ca

do

Co

ntin

uin

g P

roje

ct:

Ye

ar

4 o

f 6

Avo

ca

do

Cro

wle

y,

D.,

Sm

ith

, W

., A

rpa

ia,

M.L

.1

99

9R

oo

tsto

ck S

ele

ctio

ns f

or

Imp

rove

d S

alin

ity T

ole

ran

ce

of

Avo

ca

do

Pro

ce

ed

ing

s o

f A

vo

ca

do

Bra

insto

rmin

g 1

99

9 p

78

-80

Avo

ca

do

Cro

wle

y,

D.E

.1

99

9S

alin

ity T

ole

ran

ce

in

Avo

ca

do

Re

po

rt f

or

Pro

ject

Ye

ar

2C

alif

orn

ia A

vo

ca

do

Re

se

arc

h S

ym

po

siu

m C

alif

orn

ia A

vo

ca

do

So

cie

ty a

nd

Un

ive

rsity o

f C

alif

orn

ia,

Riv

ers

ide

p,

15

-16

Avo

ca

do

De

Ma

rtin

i, A

.1

99

7L

ett

er

to L

os A

ng

ele

s R

eg

ion

al W

ate

r Q

ua

lity C

on

tro

l

Bo

ard

re

ga

rdin

g r

esp

on

se

to

th

e p

rop

ose

d p

olic

y

revis

ion

fo

r th

e le

ve

ls o

f ch

lorid

e in

dis

ch

arg

e o

f

wa

ste

wa

ter

Zo

ne

Mu

tua

l W

ate

r C

om

pa

ny L

ett

er

to D

eb

ora

h J

. S

mith

, L

A

RW

QC

B

Avo

ca

do

Do

wn

ton

, W

.J.S

.1

97

8G

row

th a

nd

Flo

we

rin

g in

Sa

lt-s

tre

sse

d A

vo

ca

do

Tre

es

Au

str

alia

n J

ou

rna

l o

f A

gricu

ltu

ral R

eso

urc

es 2

9:

52

3-3

4

Avo

ca

do

Eh

lig,

C.F

., B

ern

ste

in,

L.

19

59

Fo

liar

Ab

so

rptio

n o

f S

od

ium

an

d C

hlo

rid

e a

s a

Fa

cto

r in

Sp

rin

kle

r Ir

rig

atio

n

Am

erica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

, V

ol. 7

4

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

2 of

12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Avo

ca

do

Em

be

lto

n,

T.W

., M

ats

um

ura

, M

., S

tore

y,

W.B

., G

arb

er,

M.J

.

19

61

Ch

lorid

e a

nd

Avo

ca

do

Ro

ots

tocks

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 4

5:

11

0-1

15

Avo

ca

do

Em

ble

ton

, T

.W.,

Ma

tsu

mu

ra,

M.,

Sto

rey,

W.B

., G

arb

er,

M.J

.

19

62

Ch

lorin

e a

nd

Oth

er

Ele

me

nts

in

Avo

ca

do

Le

ave

s a

s

Influ

en

ce

d b

y R

oo

tsto

ck

Pro

ce

ed

ing

s o

f th

e A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

Avo

ca

do

Fa

be

r, B

. 2

00

4O

ne

, O

ne

Hu

nd

red

, O

ne

Th

ou

sa

nd

T

op

ics in

Su

btr

op

ics N

ew

sle

tte

r V

ol. 2

, N

o.

2

Avo

ca

do

Fa

be

r, B

., Y

ate

s,

M.,

Arp

aia

, M

.1

99

4Ir

rig

atio

n M

an

ag

em

en

t o

f A

vo

ca

do

sC

alif

orn

ia A

vo

ca

do

So

cie

ty Y

ea

rbo

ok 7

8:

14

3-1

46

Avo

ca

do

Fa

be

r, B

.A.,

Arp

aia

, M

.L.,

Ya

tes,

M.V

.1

99

5Ir

rig

atio

n M

an

ag

em

en

t o

f A

vo

ca

do

in

a C

alif

orn

ia

Co

asta

l E

nviro

nm

en

t

Pro

ce

ed

ing

s o

f th

e W

orld

Avo

ca

do

Co

ng

ress I

II,

p 1

89

-19

5

Avo

ca

do

Fe

nn

, L

.B.,

Bin

gh

am

, F

.T.,

Oe

rtli,

J.J

.1

96

8O

n t

he

Me

ch

an

ism

of

Ch

lorid

e T

oxic

ity

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 5

2:

p 1

13

-11

6

Avo

ca

do

Ga

zit,

S.,

Ka

dm

an

, A

.1

97

6G

row

ing

Avo

ca

do

s in

Are

as o

f H

igh

Sa

linity

Pro

ce

ed

ing

s o

f th

e F

irst

Inte

rna

tio

na

l T

rop

ica

l F

ruit S

ho

rt C

ou

rse

:

Th

e A

vo

ca

do

p 5

8-6

0

Avo

ca

do

Gill

esp

ie,

H.L

.1

95

4D

eve

lop

me

nt

an

d E

va

lua

tio

n o

f C

lon

al R

oo

tsto

cks in

Th

e A

vo

ca

do

--

Ph

ase

Tw

o

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 3

8:8

7-9

5

Avo

ca

do

Go

nza

les-R

osa

s,

H.,

Sa

laza

r-G

arc

ia,

S.,

Ra

mire

z-R

eye

s,

G.,

Ro

drig

ue

z-O

ntive

ros,

J.L

., R

am

os-V

illa

se

no

r, A

.C.

20

03

Pre

limin

ary

Re

su

lts o

n I

nvitro

Se

lectio

n f

or

To

lera

nce

to

Ch

lorid

e E

xce

ss in

Avo

ca

do

Avo

ca

do

Gra

tta

n,

S.,

Oste

r, J

.2

00

2D

rou

gh

t T

ip 9

2-1

9 W

ate

r Q

ua

lity G

uid

elin

es f

or

Tre

es

an

d V

ine

s

La

nd

, A

ir a

nd

Wa

ter

Re

so

urc

es,

Un

ive

rsity o

f C

alif

orn

ia,

Da

vis

,

Ca

lifo

rnia

Avo

ca

do

Gre

en

wa

y,

H.,

Mu

nn

s,

R.

19

80

Me

ch

an

ism

s o

f S

alt T

ole

ran

ce

in

No

nh

alo

ph

yte

sA

nn

ua

l R

evie

ws in

Pla

nt

Ph

ysio

log

y 3

1:

14

9-9

0

Avo

ca

do

Gu

sta

fso

n,

C.D

.1

96

2T

he

Sa

linity P

rob

lem

in

Gro

win

g A

vo

ca

do

s

Avo

ca

do

Gu

sta

fso

n,

C.D

.1

97

6A

vo

ca

do

Wa

ter

Re

latio

ns

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 6

0:

57

-72

Avo

ca

do

Gu

sta

fso

n,C

.D.,

Ma

rch

,A.W

., B

ran

so

n,R

.L.,

Da

vis

,S.

19

73

Drip

Irr

iga

tio

n E

xp

erim

en

ts w

ith

Avo

ca

do

s in

Sa

n D

ieg

o

Co

un

ty

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 5

6:

10

9-1

12

Avo

ca

do

Ha

as,

A.R

.C.

19

36

Ch

lorin

e in

Re

latio

n t

o R

ing

-Ne

ck in

Avo

ca

do

Fru

its

Ca

lifo

rnia

Avo

ca

do

Asso

cia

tio

n Y

ea

rbo

ok 2

1:

60

-62

Avo

ca

do

Ha

as,

A.R

.C.

19

50

aC

alc

ium

in

Re

latio

n t

o t

he

Eff

ects

of

So

diu

m in

Avo

ca

do

Se

ed

ling

s

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 3

4:1

61

-16

8

Avo

ca

do

Ha

as,

A.R

.C.

19

50

bE

ffe

ct

of

So

diu

m C

hlo

rid

e o

n M

exic

an

, G

ua

tem

ala

n,

an

d W

est

Ind

ian

Avo

ca

do

Se

ed

ling

s

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 3

4:

15

3-1

60

Avo

ca

do

Ha

as,

A.R

.C.

19

50

cR

oo

tsto

ck I

nflu

en

ce

on

th

e C

om

po

sitio

n o

f S

cio

n

Avo

ca

do

Le

ave

s

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 3

4:1

49

-15

2

Avo

ca

do

Ha

as,

A.R

.C.

19

52

So

diu

m E

ffe

cts

on

Avo

ca

do

Ro

ots

tocks

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 3

7:

15

9-1

66

Avo

ca

do

Ha

as,

A.R

.C.

19

28

Re

latio

n o

f C

hlo

rin

e C

on

ten

t to

Tip

Bu

rn o

f A

vo

ca

do

Le

ave

s

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 1

2:5

7

Avo

ca

do

Ha

as,

A.R

.C.

19

29

Co

mp

ositio

n o

f A

vo

ca

do

Tre

es in

Re

latio

n t

o C

hlo

rosis

an

d T

ip-B

urn

Bo

tan

ica

l G

aze

tte

87

:42

2-4

30

Avo

ca

do

Ha

as,

A.R

.C.,

Bru

sca

, J.N

.1

95

5C

hlo

rid

e T

oxic

ity in

Avo

ca

do

s T

ests

Sh

ow

Ch

lorid

e

Ab

so

rptio

n a

nd

To

xic

ity V

ary

with

th

e S

ee

dlin

g V

arie

ty

an

d t

he

Fo

rm o

f N

itro

ge

n

Ca

lifo

rnia

Ag

ricu

ltu

re 9

(2):

11

-12

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

3 of

12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Avo

ca

do

Ha

rdin

g,

R.B

., M

ille

r, M

.P.,

Fire

ma

n,

M.

19

57

Le

af

Bu

rn o

n S

prin

kle

d C

itru

s F

acto

rs A

ffe

ctin

g L

ea

f

Ab

so

rptio

n o

f S

od

ium

an

d C

hlo

rid

e f

rom

Wa

ter

Sp

rin

kle

r-a

pp

lied

to

Citru

s a

nd

Avo

ca

do

s S

tud

ies

Ca

lifo

rnia

Ag

ricu

ltu

re 1

1(1

): 9

-10

Avo

ca

do

Ka

dm

an

, A

.1

96

3T

he

Up

take

an

d A

ccu

mu

latio

n o

f C

hlo

rid

e in

Avo

ca

do

Le

ave

s a

nd

th

e T

ole

ran

ce

of

Avo

ca

do

Se

ed

ling

s u

nd

er

Sa

line

Co

nd

itio

ns

Am

erica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

83

:28

0-2

86

Avo

ca

do

Ka

dm

an

, A

.1

96

8S

ele

ctio

n o

f A

vo

ca

do

Ro

ots

tock S

uita

ble

fo

r U

se

with

Sa

line

Irr

iga

tio

n W

ate

r

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 5

2:

14

5-1

47

Avo

ca

do

Ka

dm

an

, A

. a

nd

Be

n-Y

a'a

co

v,

A.

19

69

Se

lectio

n o

f R

oo

tsto

cks a

nd

Oth

er

Wo

rk R

ela

ted

to

Sa

linity a

nd

Lim

e

Th

e D

ivis

ion

of

Su

btr

op

ica

l A

gricu

ltu

re.

Th

e V

olc

an

i In

stitu

te o

f

Ag

ricu

ltu

ral R

ese

arc

h,

Se

c.

B,

p 2

3-4

0

Avo

ca

do

Ku

rtz,

C.,

Gu

il, I

., K

lein

, I.

19

92

Wa

ter

Ra

te E

ffe

cts

on

Th

ree

Avo

ca

do

Cu

ltiv

ars

Pro

ce

ed

ing

s o

f S

eco

nd

Wo

rld

Avo

ca

do

Co

ng

ress p

35

7-3

64

Avo

ca

do

La

ha

v,

E.,

Aycic

eg

i-L

ow

en

ga

rt,

A.

20

03

Avo

ca

do

Min

era

l N

utr

itio

n t

he

Wa

ter-

Nu

trie

nts

Re

latio

nsh

ip

Pro

ce

ed

ing

s V

Wo

rld

Avo

ca

do

Co

ng

ress (

Acta

s V

Co

ng

reso

Mu

nd

ial d

el A

gu

aca

te)

p 3

49

-35

7

Avo

ca

do

La

ha

v,

E.,

Ste

inh

ard

t, R

., K

alm

ar,

D.

19

92

Wa

ter

Re

qu

ire

me

nts

an

d E

ffe

ct

of

Sa

linity in

an

Avo

ca

do

Orc

ha

rd o

n C

lay S

oil

Pro

ce

ed

ing

s o

f S

eco

nd

Wo

rld

Avo

ca

do

Co

ng

ress p

23

2-3

30

Avo

ca

do

Ma

as,

E.V

.1

98

4S

alt T

ole

ran

ce

of

Pla

nts

In H

an

db

oo

k o

f P

lan

t S

cie

nce

in

Ag

ricu

ltu

re.

B.R

. C

hristie

(e

d.)

.

CR

C P

ress,

Bo

ca

Ra

ton

, F

lorid

a

Avo

ca

do

Me

iri, A

., Y

an

ai, U

., B

ern

ste

in,

N.,

Str

ul, R

.,

Zilb

ers

tain

e,

M.

19

99

Irrig

atio

n F

req

ue

ncy A

ffe

cts

So

il S

alin

ity o

f D

rip

Irrig

ate

d A

vo

ca

do

Pro

ce

ed

ing

s o

f A

vo

ca

do

Bra

insto

rmin

g 1

99

9 p

81

-83

Avo

ca

do

Me

ng

e,

J.A

., M

au

k,

P.A

., Z

en

tmye

r, G

.1

99

9C

on

tro

l o

f P

hyto

ph

tho

ra C

inn

am

om

i R

oo

t R

ot

in

Avo

ca

do

Pro

ce

ed

ing

s o

f A

vo

ca

do

Bra

insto

rmin

g 1

99

9

Avo

ca

do

Me

ye

r, J

.L.,

Ya

tes,

M.V

., S

tott

lem

ye

r, D

.E.,

Ta

ke

le,

E.,

Arp

aia

, M

.L.,

Be

nd

er,

G.S

.,

Witn

ey,

G.W

.

19

92

Irrig

atio

n a

nd

Fe

rtili

za

tio

n M

an

ag

em

en

t o

f A

vo

ca

do

sP

roc.

of

Se

co

nd

Wo

rld

Avo

ca

do

Co

ng

ress,

p 2

81

-28

8

Avo

ca

do

Mic

ke

lba

rt,

M.V

., A

rpa

ia,

M.L

.2

00

2R

oo

tsto

ck I

nflu

en

ce

s C

ha

ng

es in

Io

n C

on

ce

ntr

atio

ns,

Gro

wth

, a

nd

Ph

oto

syn

the

sis

of

'Ha

ss' A

vo

ca

do

Tre

es in

Re

sp

on

se

to

Sa

linity

Jo

urn

al o

f A

me

rica

n H

ort

icu

ltu

ral S

cie

nce

12

7 (

4):

64

9-6

55

Avo

ca

do

Mo

ntg

om

ery

Wa

tso

n1

99

7C

ity o

f E

sco

nd

ido

's A

vo

ca

do

Pilo

t P

roje

ct

An

Eva

lua

tio

n

of

Re

cla

ime

d W

ate

r fo

r U

se

on

Avo

ca

do

s F

ive

Ye

ar

Fin

al a

nd

Su

mm

ary

Re

po

rt

Mo

ntg

om

ery

Wa

tso

n

Avo

ca

do

Ne

vin

, J.,

Lo

va

tt,

C.J

.1

98

7P

hysio

log

ica

l C

ha

ng

es in

Avo

ca

do

Le

ave

s d

urin

g

Wa

ter-

de

ficit S

tre

ss

19

87

Su

mm

ary

of

Avo

ca

do

Re

se

arc

h,

Avo

ca

do

Re

se

arc

h

Ad

vis

ory

Co

mm

itte

e,

Un

ive

rsity o

f C

alif

orn

ia,

Riv

ers

ide

, p

15

Avo

ca

do

Oste

r, J

.D.

19

99

Wa

ter

Pro

du

ctio

n F

un

ctio

n M

od

el fo

r S

alin

e I

rrig

atio

n

Wa

ters

No

ne

cite

d

Avo

ca

do

Oste

r, J

.D.

19

99

Sa

linity P

an

el S

um

ma

ryP

roce

ed

ing

s o

f A

vo

ca

do

Bra

insto

rmin

g '9

9,

p 7

5-7

7

Avo

ca

do

Oste

r, J

.D.,

Arp

aia

, M

.L.

20

02

Se

ttin

g T

MD

Ls f

or

Sa

linity a

nd

Ch

lorid

e B

ase

d o

n t

he

ir

Eff

ects

on

Avo

ca

do

(H

ass)

Pro

du

ctivity

In:

J.C

. M

cG

rah

an

(e

d).

Pro

ce

ed

ing

s,

He

lpin

g I

rrig

ate

d

Ag

ricu

ltu

re A

dju

st

to T

MD

Ls,

Sa

cra

me

nto

, C

alif

orn

ia,

Octo

be

r 2

3-

26

, 2

00

2.

24

1-2

52

. U

.S.

Co

mm

itte

e o

n I

rrig

atio

n a

nd

Dra

ina

ge

,

De

nve

r, C

olo

rad

o

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

4 of

12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Avo

ca

do

Oste

r, J

.D.,

Arp

aia

, M

.L.

19

92

'Ha

ss' A

vo

ca

do

Re

sp

on

se

to

Sa

linity a

s I

nflu

en

ce

d b

y

Clo

na

l R

oo

tsto

cks

Pro

ce

ed

ing

s o

f th

e S

eco

nd

Wo

rld

Avo

ca

do

Co

ng

ress p

20

9-2

14

Avo

ca

do

Oste

r, J

.D.,

Bro

ka

w,

R.,

Str

oh

ma

n,

R.A

.,

Tra

cy,

J.E

.

19

88

Influ

en

ce

of

Sa

linity a

nd

Ro

ots

tock in

Ha

ss S

ee

dlin

g

Gro

wth

Su

mm

ary

of

Avo

ca

do

Re

se

arc

h,

Avo

ca

do

Re

se

arc

h A

dvis

ory

Co

mm

itte

e,

Un

ive

rsity o

f C

alif

orn

ia,

Riv

ers

ide

p 8

-11

Avo

ca

do

Pa

rtid

a,

G.J

.,2

00

2D

ecla

ratio

n o

f D

r. G

reg

ory

J.

Pa

rtid

a H

ort

icu

ltu

re/P

lan

t

an

d S

oil

Scie

nce

De

pt.

Ca

lifo

rnia

Sta

te P

oly

tech

nic

Un

ive

rsity P

om

on

a,

Ca

lifo

rnia

Co

un

ty S

an

ita

tio

n D

istr

icts

of

Lo

s A

ng

ele

s C

ou

nty

Avo

ca

do

Pa

tel, P

.M.,

Wa

llace

, A

., M

ue

ller,

R.T

.1

97

6S

alt T

ole

ran

ce

of

Hu

nta

las C

om

pa

red

with

Oth

er

Avo

ca

do

Ro

ots

tocks

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 1

97

5-7

6:

78

-79

Avo

ca

do

Re

inh

old

, L

. a

nd

Gu

y M

. 2

00

2F

un

ctio

n o

f M

em

bra

ne

Tra

nsp

ort

Syste

ms u

nd

er

Sa

linity:

Pla

sm

a M

em

bra

ne

Sa

linity:

En

viro

nm

en

t-P

lan

ts-M

ole

cu

les.

Ed

. A

. L

äu

ch

li a

nd

U.

Lü

ttg

e.

Bo

sto

n,

MA

: K

luw

er

Aca

de

mic

Pu

blis

he

rs

Avo

ca

do

Ric

ha

rds,

S.J

., W

ee

ks,

L.V

., J

oh

nsto

n,

J.C

.1

95

8E

ffe

cts

of

Irrig

atio

n T

rea

tme

nts

an

d R

ate

s o

f N

itro

ge

n

Fe

rtili

za

tio

n o

n Y

ou

ng

Ha

as A

vo

ca

do

Tre

es.

I. G

row

th

Re

sp

on

se

to

Irr

iga

tio

n

Pro

ce

ed

ing

s o

f th

e A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

71

:29

2-2

97

Avo

ca

do

Sa

laza

r-G

arc

ia,

S.,

Co

rte

s-F

lore

s,

J.I

.1

98

8L

ea

f S

co

rch

an

d M

ine

ral N

utr

itio

n o

f A

vo

ca

do

Tre

es

Irrig

ate

d W

ith

Sa

line

Wa

ter

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 7

2:

22

9-2

35

Avo

ca

do

Sa

laza

r-G

arc

ia,

S.,

La

rqu

e'-S

aa

ve

dra

, A

.1

98

5E

ffe

ct

of

Pro

gre

ssiv

e S

oil

Sa

linity o

n t

he

Le

af

Wa

ter

Po

ten

tia

l a

nd

Sto

ma

tal C

on

du

cta

nce

in

Avo

ca

do

(Pe

rse

a A

me

rica

na

Mill

.)

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 6

9:

10

1-1

04

Avo

ca

do

Se

rra

no

, R

.2

00

2H

alo

tole

ran

ce

Ge

ne

s in

Ye

ast

Sa

linity:

En

viro

nm

en

t-P

lan

ts-M

ole

cu

les.

Ed

. A

. L

äu

ch

li a

nd

U.

Lü

ttg

e.

Bo

sto

n,

MA

: K

luw

er

Aca

de

mic

Pu

blis

he

rs

Avo

ca

do

Sh

alh

eve

t, J

.1

99

9S

alin

ity a

nd

Wa

ter

Ma

na

ge

me

nt

in A

vo

ca

do

Pro

ce

ed

ing

s o

f A

vo

ca

do

Bra

insto

rmin

g 1

99

9,

p 8

4-9

1

Avo

ca

do

Sh

alh

eve

t, J

.1

99

4U

sin

g W

ate

r o

f M

arg

ina

l Q

ua

lity f

or

Cro

p P

rod

uctio

n:

Ma

jor

Issu

es

Ag

ricu

ltu

ral W

ate

r M

an

ag

em

en

t 2

5:

23

3-2

69

Avo

ca

do

Slo

wik

, K

., L

ab

an

au

ska

s,

C.K

., S

tolz

y,

L.H

.,

Ze

ntm

ye

r, G

.A.

19

79

Influ

en

ce

of

Ro

ots

tocks,

So

il O

xyg

en

, a

nd

So

il M

ois

ture

on

th

e U

pta

ke

an

d T

ran

slo

ca

tio

n o

f N

utr

ien

ts in

Yo

un

g

Avo

ca

do

Pla

nts

Jo

urn

al o

f A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

10

4(2

):1

72

-

17

5

Avo

ca

do

Sp

ieg

el, Y

., N

eze

r, D

. K

afk

afi,

U.

19

87

Th

e R

ole

of

Ca

Nu

tritio

n o

n F

usa

riu

m-w

ilt S

yn

dro

me

in

Mu

skm

elo

n

Jo

urn

al o

f P

hyto

pa

tho

log

y 1

18

: 2

00

-22

6

Avo

ca

do

Ste

inh

ard

t, R

., K

alm

ar,

D.,

Mia

ri,

A.,

La

ha

v,

E.

19

95

VC

65

Ro

ots

tock I

nd

ucin

g S

alin

ity-r

esis

tan

ce

an

d

Pro

du

ctivity t

o F

ue

rte

Avo

ca

do

Alo

n H

an

ote

a 4

9 (

10

): 4

60

Avo

ca

do

Th

om

as,

E.E

.1

93

2E

ffe

cts

of

Ch

lorid

es in

th

e S

oil

on

Avo

ca

do

Tre

es

Ca

lifo

rnia

Avo

ca

do

Asso

cia

tio

n Y

ea

rbo

ok 1

7:

48

-49

Avo

ca

do

Tra

sk,

E.

19

60

So

me

Fa

cto

rs A

ffe

ctin

g t

he

Accu

mu

latio

n o

f C

hlo

rid

es

in A

vo

ca

do

So

ils

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 4

4:

38

-39

Avo

ca

do

UC

Co

op

era

tive

Exte

nsio

n2

00

3T

op

ics in

Su

btr

op

ics N

ew

sle

tte

rV

ol 1

, N

o.

4

Avo

ca

do

UC

Co

op

era

tive

Exte

nsio

n2

00

4T

op

ics in

Su

btr

op

ics N

ew

sle

tte

rV

ol 2

, N

o.

2

Avo

ca

do

UC

Co

op

era

tive

Exte

nsio

n2

00

4T

op

ics in

Su

btr

op

ics N

ew

sle

tte

rV

ol 2

, N

o.

1

Avo

ca

do

UC

Co

op

era

tive

Exte

nsio

n2

00

3T

op

ics in

Su

btr

op

ics N

ew

sle

tte

rV

ol 1

, N

o.

3

Avo

ca

do

UC

Da

vis

No

ne

Op

era

tio

ns

Avo

ca

do

UC

Da

vis

No

ne

Avo

ca

do

in

a D

rou

gh

t

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

5 of

12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Avo

ca

do

UC

Da

vis

No

ne

On

e,

Hu

nd

red

, T

ho

usa

nd

Avo

ca

do

UC

Da

vis

No

ne

Avo

ca

do

s in

Ju

ne

Avo

ca

do

Un

ite

d S

tate

s S

alin

ity L

ab

ora

tory

19

54

Dia

gn

osis

an

d I

mp

rove

me

nt

of

Sa

line

an

d A

lka

li S

oils

Ag

ricu

ltu

re H

an

db

oo

k N

o.

60

. U

.S.

De

pa

rtm

en

t o

f A

gricu

ltu

re

Avo

ca

do

Wa

llace

, A

., S

ha

nn

on

, L

.M.,

No

rth

, C

.P.,

Mu

elle

r, R

.T.

19

55

Gla

ssh

ou

se

Stu

die

s o

n t

he

Sa

lt T

ole

ran

ce

an

d G

row

th

of

Pe

rse

a F

locco

sa

as a

Ro

ots

tock

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok 3

9:

17

9-1

83

Avo

ca

do

Wh

iley,

A.W

., P

eg

g,

K.G

., S

ara

na

h,

J.G

.1

98

6T

he

Use

of

Le

af

Xyle

m W

ate

r P

ote

ntia

l to

Me

asu

re t

he

Imp

act

of

Ph

yto

ph

tho

ra R

oo

t R

ot

Activity in

Avo

ca

do

(Pe

rse

a A

me

rica

na

)

Acta

Ho

rtic

ultu

re (

ISH

S)

17

5:

35

1-3

56

(a

bstr

act

on

ly)

Avo

ca

do

Wh

iley,

A.W

., S

ara

na

h,

J.B

., C

ull,

B.W

.,

Pe

gg

, K

.G.

19

88

Ma

na

ge

Avo

ca

do

Tre

e G

row

th C

ycle

s f

or

Pro

du

ctivity

Ga

ins

Qu

ee

nsla

nd

Ag

ricu

ltu

ral Jo

urn

al, p

29

-36

Avo

ca

do

Wie

sm

an

, Z

.1

99

5R

oo

tsto

ck a

nd

Nitra

te I

nvo

lve

me

nt

in 'E

ttin

ge

r' A

vo

ca

do

Re

sp

on

se

to

Ch

lorid

e S

tre

ss

Scie

ntia

Ho

rtic

ultu

rae

62

:33

-43

Avo

ca

do

Wu

tsch

er,

H.K

., M

axw

ell,

N.P

.1

97

5S

ea

so

na

l C

ha

ng

es in

12

Le

af

Nu

trie

nts

of

'Lu

la'

Avo

ca

do

with

Drip

an

d F

loo

d I

rrig

atio

n

HO

RT

SC

IEN

CE

, 1

0(5

):5

12

-51

4

Str

aw

be

rry

AN

ZE

CC

19

92

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mm

ary

of

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ide

line

s f

or

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atio

n W

ate

r Q

ua

lity

Extr

acte

d f

rom

th

e A

ustr

alia

n W

ate

r Q

ua

lity G

uid

elin

es f

or

Fre

sh

& M

arin

e W

ate

rs

Str

aw

be

rry

Bro

wn

, J.G

. a

nd

Vo

th,

V.

19

55

Sa

lt D

am

ag

e t

o S

tra

wb

err

ies

Ca

lifo

rnia

Ag

ricu

ltu

re,

p 1

1-1

2

Str

aw

be

rry

Ca

lifo

rnia

Fe

rtili

ze

r A

sso

cia

tio

n,

So

il

Imp

rove

me

nt

Co

mm

itte

e

19

85

We

ste

rn F

ert

ilize

r H

an

db

oo

k

Str

aw

be

rry

Ca

lifo

rnia

Str

aw

be

rry C

om

mis

sio

n W

eb

site

-

Ind

ustr

y C

om

mu

nic

atio

ns

20

04

Ind

ustr

y B

ackg

rou

nd

er

Ca

lifo

rnia

Str

aw

be

rrie

s a

t a

Gla

nce

- 2

00

4

ww

w.c

als

tra

wb

err

y.c

om

Str

aw

be

rry

Div

isio

n o

f A

gricu

ltu

ral a

nd

Na

tura

l

Re

so

urc

es

19

94

Inte

gra

ted

Pe

st

Ma

na

ge

me

nt

for

Str

aw

be

rrie

sP

ub

lica

tio

n 3

35

Str

aw

be

rry

Do

ma

to,

P.,

Gle

aso

n,

M.,

Le

wis

, D

.2

00

0P

rod

uctio

n G

uid

e f

or

Co

mm

erc

ial S

tra

wb

err

ies

Iow

a S

tate

Un

ive

rsity U

niv

ers

ity E

xte

nsio

n

Str

aw

be

rry

Eh

lig,

C.F

.1

96

1S

alt T

ole

ran

ce

of

Str

aw

be

rrie

s U

nd

er

Sp

rin

kle

r

Irrig

atio

n

Am

erica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

77

: 3

76

-37

9

Str

aw

be

rry

Eh

lig,

C.F

., a

nd

Be

rnste

in,

L.

19

58

Sa

lt T

ole

ran

ce

of

Str

aw

be

rrie

sA

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

72

: 1

98

-20

6

Str

aw

be

rry

El-F

arh

an

, A

.H.,

Pritt

s,

M.P

.1

99

7W

ate

r R

eq

uire

me

nts

an

d W

ate

r S

tre

ss in

Str

aw

be

rry

Ad

va

nce

s in

Str

aw

be

rry R

ese

arc

h,

Vo

lum

e 1

6

Str

aw

be

rry

Giu

ffrid

a,

F.,

Le

on

ard

i, C

., N

oto

, G

.2

00

1R

esp

on

se

of

So

ille

ss G

row

n S

tra

wb

err

y t

o D

iffe

ren

t

Sa

linity L

eve

ls in

th

e N

utr

ien

t S

olu

tio

n

Acta

Ho

rtic

ultu

re 5

59

, IS

HS

, p

67

5-6

80

Str

aw

be

rry

Gra

tta

n,

S.R

.1

99

1Ir

rig

atio

n M

an

ag

em

en

t fo

r S

alin

ity C

on

tro

l in

Str

aw

be

rry

Pro

du

ctio

n

Str

aw

be

rry N

ew

s B

ulle

tin

, C

alif

orn

ia S

tra

wb

err

y A

dvis

ory

Bo

ard

Str

aw

be

rry

Ha

nso

n,

B.

an

d B

en

dix

en

, W

.2

00

4D

rip

Irr

iga

tio

n E

va

lua

ted

in

Sa

nta

Ma

ria

Va

lley

Str

aw

be

rrie

s

Ca

lifo

rnia

Ag

ricu

ltu

re,

v 5

8,

No

. 1

, p

48

-53

Str

aw

be

rry

Ke

pe

ne

k,

K.

an

d K

oyu

ncu

, F

.2

00

2S

tud

ies o

n t

he

Sa

lt T

ole

ran

ce

of

So

me

Str

aw

be

rry

Cu

ltiv

ars

un

de

r G

lassh

ou

se

Acta

Ho

rt.

57

3,

ISH

S,

p 2

97

-30

4

Str

aw

be

rry

La

Ma

lfa

, G

.N

on

eW

orld

Fe

rtili

ze

r U

se

Ma

nu

al, S

tra

wb

err

yIs

titu

to d

i O

rtic

oltu

ra e

Flo

rico

ltu

ra,

Un

ive

rsita

de

gli

Stu

dy d

i

Ca

tan

ia,

Ita

ly

Str

aw

be

rry

La

mb

ert

s,

D.,

Sch

reve

ns,

E.,

Le

tta

ni, L

., V

er

Be

rne

, A

.

19

89

Ch

lorid

e E

ffe

cts

on

Str

aw

be

rry

Acta

Ho

rtic

ultu

rae

26

5,

Str

aw

be

rry S

ym

po

siu

m,

p 2

85

-29

0

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

6 of

12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Str

aw

be

rry

La

rso

n,

K.D

., K

oik

e,

S.,

Za

lom

, F

., P

olit

o,

V.,

Sh

ow

, E

.

20

02

Str

aw

be

rry F

ruit B

ron

zin

g R

ese

arc

h S

um

ma

ryC

alif

orn

ia S

tra

wb

err

y C

om

mis

sio

n R

ese

arc

h R

ep

ort

Str

aw

be

rry

La

rso

n,

K.D

., K

oik

e,

S.,

Za

lom

, F

., S

julin

, T

.,

Ba

ste

r, B

.

20

01

Str

aw

be

rry F

ruit B

ron

zin

g R

ese

arc

h S

um

ma

ry,

19

99

-

20

00

Ca

lifo

rnia

Str

aw

be

rry C

om

mis

sio

n R

ese

arc

h R

ep

ort

Str

aw

be

rry

Ma

as,

J.

L.

19

97

Co

mp

en

diu

m o

f S

tra

wb

err

y D

ise

ase

sA

me

rica

n P

hyto

pa

tho

log

ica

l S

ocie

ty U

SD

A A

RS

Str

aw

be

rry

Ma

nito

ba

Ag

ricu

ltu

re,

Fo

od

an

d R

ura

l

Initia

tive

s

20

01

Str

aw

be

rry -

Site

Se

lectio

n a

nd

Str

aw

be

rry -

Oth

er

Pro

ble

ms

ww

w.g

ov.m

b-c

a/a

gricu

ltu

re/c

rop

s/f

ruity/b

1b

01

s1

4.h

tml

Str

aw

be

rry

Sch

rad

er,

W.L

. a

nd

We

lch

, N

.C.

19

90

Sa

linity M

an

ag

em

en

t in

Str

aw

be

rry P

rod

uctio

nS

tra

wb

err

y N

ew

s B

ulle

tin

, C

alif

orn

ia S

tra

wb

err

y A

dvis

ory

Bo

ard

Str

aw

be

rry

Un

ive

rsity o

f C

alif

orn

ia1

99

9C

rop

Pro

file

fo

r S

tra

wb

err

ies in

Ca

lifo

rnia

Un

ive

rsity o

f C

alif

orn

ia F

ruit a

nd

Nu

t R

ese

arc

h a

nd

In

form

atio

n

Ce

nte

r W

eb

Site

Str

aw

be

rry

Vo

th,

V.

an

d B

rin

gh

urs

t, R

.S.

19

67

Th

e A

ffe

ct

of

Cu

ltu

ral P

ractice

s o

n S

alin

ity

Str

aw

be

rry N

ew

s B

ulle

tin

, C

alif

orn

ia S

tra

wb

err

y A

dvis

ory

Bo

ard

V.

XII

I, B

ulle

tin

#4

Str

aw

be

rry

We

lch

, N

.C.

et

al.

No

ne

Str

aw

be

rry P

rod

uctio

n in

Ca

lifo

rnia

Co

op

era

tive

Exte

nsio

n U

niv

ers

ity o

f C

alif

orn

ia,

Div

isio

n o

f

Ag

ricu

ltu

re a

nd

Na

tura

l R

eso

urc

es,

Le

afle

t N

o.

29

59

.

Str

aw

be

rry

We

lch

, N

. a

nd

Be

ute

l, J

.1

98

7S

um

me

r P

lan

tin

g -

Str

aw

be

rrie

s -

La

nd

Pre

pa

ratio

n -

So

il A

me

nd

me

nt

- P

rep

lan

t F

ert

ilize

r

Str

aw

be

rry N

ew

s B

ulle

tin

, C

alif

orn

ia S

tra

wb

err

y A

dvis

ory

Bo

ard

Str

aw

be

rry

Wic

hm

an

n,

W.

Ed

.1

99

6-

20

04

Wo

rld

Fe

rtili

ze

r U

se

Ma

nu

al

In

tern

atio

na

l F

ert

ilize

r In

du

str

y A

sso

cia

tio

n

Nu

rse

ry

Cro

ps

Ca

bre

ra,

R.

I.2

00

3E

va

lua

tin

g W

ate

r Q

ua

lity f

or

Orn

am

en

tal P

lan

t

Pro

du

ctio

n

Th

e S

tate

Un

ive

rsity o

f N

ew

Je

rse

y R

utg

ers

Co

op

era

tive

Exte

nsio

n F

act

Sh

ee

t 8

93

Nu

rse

ry

Cro

ps

Ca

rma

n,

H.F

. a

nd

Ro

drig

ue

z,

A.M

.2

00

4E

co

no

mic

Co

ntr

ibu

tio

ns o

f th

e C

alif

orn

ia N

urs

ery

Ind

ustr

y

Gia

nn

ini F

ou

nd

atio

n o

f A

gricu

ltu

ral E

co

no

mic

s

Nu

rse

ry

Cro

ps

Ca

rpe

nte

r, E

.D.

19

70

Sa

lt T

ole

ran

ce

of

Orn

am

en

tal P

lan

tsA

me

rica

n N

urs

ery

ma

n

Nu

rse

ry

Cro

ps

CR

WQ

CB

, L

os A

ng

ele

s R

eg

ion

20

01

Ba

sin

Pla

n A

me

nd

me

nt

to R

evis

e t

he

Re

ach

De

fin

itio

ns

an

d C

hlo

rid

e W

ate

r Q

ua

lity O

bje

ctive

s f

or

Ca

lleg

ua

s

Cre

ek

Dra

ft S

taff

Re

po

rt

Nu

rse

ry

Cro

ps

Ba

iley,

D.,

Bild

erb

ack,

T.,

Bir,

D.

19

99

Wa

ter

Co

nsid

era

tio

n f

or

Co

nta

ine

r P

rod

uctio

n o

f P

lan

tsN

C S

tate

Un

ive

rsity H

ort

icu

ltu

re I

nfo

rma

tio

n L

ea

fle

t N

o.

55

7

Nu

rse

ry

Cro

ps

Be

rnste

in,

L.

19

64

Re

du

cin

g S

alt I

nju

ry t

o O

rna

me

nta

l S

hru

bs in

th

e W

est

U.S

. D

ep

t. o

f A

g.

- H

om

e a

nd

Ga

rde

n B

ulle

tin

No

. 9

5

Nu

rse

ry

Cro

ps

Be

rnste

in,

L.,

Fra

nco

is,

L.E

., C

lark

, R

.A.

19

72

Sa

lt T

ole

ran

ce

of

Orn

am

en

tal S

hru

bs a

nd

Gro

un

d

Co

ve

rs

Jo

urn

al o

f A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

97

(4):

55

0-

55

6

Nu

rse

ry

Cro

ps

Eh

lig,

C.F

., B

ern

ste

in,

L.

19

59

Fo

liar

Ab

so

rptio

n o

f S

od

ium

an

d C

hlo

rid

e a

s a

Fa

cto

r in

Sp

rin

kle

r Ir

rig

atio

n

Jo

urn

al o

f A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

, 7

4:6

61

-67

0

Nu

rse

ry

Cro

ps

Fa

rnh

am

, D

.S.,

Ha

se

k,

R.F

., P

au

l, J

.L.

19

93

Wa

ter

Qu

alit

y I

ts E

ffe

cts

on

Orn

am

en

tal P

lan

tsC

oo

pe

rative

Exte

nsio

n U

niv

ers

ity o

f C

alif

orn

ia D

ivis

ion

of

Ag

ricu

ltu

re a

nd

Na

tura

l R

eso

urc

es L

ea

fle

t 2

99

5

Nu

rse

ry

Cro

ps

Fra

nco

is,

L.E

.1

98

2S

alt T

ole

ran

ce

of

Eig

ht

Orn

am

en

tal T

ree

Sp

ecie

sJo

urn

al o

f A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

10

7(1

:)6

6-

68

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

7 of

12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Nu

rse

ry

Cro

ps

Fra

nco

is,

L.E

. a

nd

Cla

rk,

R.A

.1

97

8S

alt T

ole

ran

ce

of

Orn

am

en

tal S

hru

bs,

Tre

es,

an

d

Ice

pla

nt

Jo

urn

al o

f A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

10

3(2

):2

80

-

28

3

Nu

rse

ry

Cro

ps

Gra

tta

n,

S.R

.2

00

2Ir

rig

atio

n W

ate

r S

alin

ity a

nd

Cro

p P

rod

uctio

nU

niv

ers

ity o

f C

alif

orn

ia A

NR

Pu

blic

atio

n 8

06

6,

FW

QP

Re

fere

nce

Sh

ee

t 9

.10

Nu

rse

ry

Cro

ps

Jo

hn

so

n,

G.

an

d Z

ha

ng

, H

.N

on

eC

lassific

atio

n o

f Ir

rig

atio

n W

ate

r Q

ua

lity

Okla

ho

ma

Sta

te U

niv

ers

ity C

oo

pe

rative

Exte

nsio

n S

erv

ice

F-

24

01

Nu

rse

ry

Cro

ps

Lin

dse

y,

P.

19

98

Re

cycle

d L

an

dsca

pe

Irr

iga

tio

n W

ate

r a

nd

Orn

am

en

tal

Pla

nt

Co

mp

atib

ility

Stu

dy

Slo

sso

n R

ep

ort

Nu

rse

ry

Cro

ps

Lu

nin

, J.

an

d S

tew

art

, F

.B.

19

61

Th

e E

ffe

ct

of

So

il S

alin

ity o

n A

za

lea

s a

nd

Ca

me

llia

sJo

urn

al o

f A

me

rica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

77

:52

8-5

32

Nu

rse

ry

Cro

ps

Lu

nt,

O.R

., K

oh

l, H

.C.,

Ko

fra

ne

k,

A.M

.1

95

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Ho

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ultu

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68

:53

7-5

44

Nu

rse

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ps

Lu

nt,

O.R

., K

oh

l, H

.C.

Jr.

, K

ofr

an

ek,

A.M

.1

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ole

ran

ce

of

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alin

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69

:54

3-5

48

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.1

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an

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71

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cie

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in

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ricu

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re.

(ed

.) B

.R.

Ch

ristie

-

CR

C P

ress I

nc.,

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l. I

I, p

. 5

7-7

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Nu

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.1

99

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Sa

lt T

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Ag

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pte

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3:2

62

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4

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cie

nce

81

:55

6-5

61

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nk,

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an

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eib

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Ph

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log

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6:4

78

-48

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Pe

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L.P

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rub

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niv

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erm

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t E

xte

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ea

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ph

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ustr

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o.

11

Nu

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xa

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&M

Un

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rig

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Nu

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Cro

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To

wn

se

nd

, A

.M.

19

80

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sp

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c.

Ho

rt.

Sci. 1

05

(6):

87

8-8

83

Nu

rse

ry

Cro

ps

We

ige

l, R

.C.

Jr.

, S

ch

illin

ge

r, J

.A.,

McC

aw

,

B.A

., G

au

ch

, H

.G.,

Hsia

o,

E.

19

73

Nu

trie

nt-

nitra

te L

eve

ls a

nd

th

e A

ccu

mu

latio

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f

Ch

lorid

e in

Le

ave

s o

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na

p B

ea

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nd

Ro

ots

of

So

yb

ea

ns

Cro

p S

cie

nce

, V

ol. 1

3:4

11

-41

2

Nu

rse

ry

Cro

ps

Wu

, L

., C

he

n,

J.,

Lin

, H

., V

an

Ma

ntg

em

, P

.,

Ha

riva

nd

i, M

.A.,

Ha

rdin

g,

J.A

.

19

95

Eff

ects

of

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ge

ne

ran

t W

aste

wa

ter

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row

th

an

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on

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Nu

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Cro

ps

Wu

, L

., H

ariva

nd

i, M

.A.,

Ha

rdin

g,

J.A

.1

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nd

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ran

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or

Lo

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wa

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l

Nu

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Wu

, L

., G

uo

, X

., H

ariva

nd

i, A

., W

ate

rs,

R.,

Bro

wn

, J.

19

99

Stu

dy o

f C

alif

orn

ia N

ative

Gra

ss a

nd

La

nd

sca

pe

Pla

nt

Sp

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s f

or

Re

cycle

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rig

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Ca

lifo

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La

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sca

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s a

nd

Ga

rde

ns

Slo

sso

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ep

ort

Nu

rse

ry

Cro

ps

Wu

, L

., G

uo

, X

., B

row

n,

J.

20

00

Stu

die

s o

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ecycle

d W

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rig

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of

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Co

nd

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Nu

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Cro

ps

Wu

, L

., G

uo

, X

., H

un

ter,

K.,

Za

go

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E.,

Wa

ters

, R

., B

row

n,

J.

20

01

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Wu

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47

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49

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Nu

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Cro

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Wu

, L

., H

ard

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., H

ariva

nd

i, M

.A.

19

98

Stu

die

s o

f R

ecycle

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rig

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Eff

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of

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nd

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pe

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Sp

ecie

s a

nd

Orn

am

en

tal G

rasse

s

Slo

sso

n R

ep

ort

Ge

ne

ral

Info

rma

tio

n

An

de

rso

n,

S.

No

ne

Ch

lorid

e B

asic

sA

gro

no

mic

Lib

rary

, B

asic

In

form

atio

n a

bo

ut

Ch

lorid

e a

s a

Pla

nt

Nu

trie

nt

Ge

ne

ral

Info

rma

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AN

ZE

CC

19

92

Au

str

alia

n W

ate

r Q

ua

lity G

uid

elin

es f

or

Fre

sh

& M

arin

e

Wa

ters

Ge

ne

ral

Info

rma

tio

n

Arizo

na

Sta

te U

niv

ers

ity

No

ne

Wh

at

is a

Sa

lt?

ca

ctu

s.e

ast.

asu

.ed

u w

eb

site

Ge

ne

ral

Info

rma

tio

n

Aye

rs,

R.S

.1

97

7Q

ua

lity o

f W

ate

r fo

r Ir

rig

atio

nJo

urn

al o

f th

e I

rrig

atio

n a

nd

Dra

ina

ge

Div

isio

n

Ge

ne

ral

Info

rma

tio

n

Aye

rs,

R.S

., a

nd

Bra

nso

n,

R.L

.1

97

5G

uid

elin

es f

or

Inte

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tatio

n o

f W

ate

r Q

ua

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or

Ag

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ltu

re

UC

Be

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ley C

om

mitte

e o

f C

on

su

lta

nts

Wa

ter

Re

so

urc

es C

en

ter

Arc

hiv

es.

UC

Be

rke

ley

Ge

ne

ral

Info

rma

tio

n

Aye

rs,

R.S

., W

estc

ot,

D.W

.1

98

5W

ate

r Q

ua

lity f

or

Ag

ricu

ltu

reF

AO

Irr

iga

tio

n a

nd

Dra

ina

ge

Pa

pe

r 2

9 R

ev.

1

Ge

ne

ral

Info

rma

tio

n

Be

rnste

in,

L.

19

64

Sa

lt T

ole

ran

ce

of

Pla

nts

So

il a

nd

Wa

ter

Co

nse

rva

tio

n R

ese

arc

h D

ivis

ion

, A

gricu

ltu

ral

Re

se

arc

h S

erv

ice

, W

ash

ing

ton

, D

.C.

Ge

ne

ral

Info

rma

tio

n

Be

rnste

in,

L.

Sa

lt T

ole

ran

ce

of

Fru

it C

rop

sA

gricu

ltu

ral R

ese

arc

h S

erv

ice

, U

.S.

De

pa

rtm

en

t o

f A

gricu

ltu

re

Ge

ne

ral

Info

rma

tio

n

Be

rnste

in,

L.

19

67

Qu

an

tita

tive

Asse

ssm

en

t o

f Ir

rig

atio

n W

ate

r Q

ua

lity

Wa

ter

Qu

alit

y C

rite

ria

, A

ST

M S

TP

41

6,

p 5

1

Ge

ne

ral

Info

rma

tio

n

Be

rnste

in,

L.

an

d F

ran

co

is,

L.E

.1

97

3L

ea

ch

ing

Re

qu

ire

me

nt

Stu

die

s:

Se

nsitiv

ity o

f A

lfa

lfa

to

Sa

linity o

f Ir

rig

atio

n a

nd

Dra

ina

ge

Wa

ters

Pro

ce

ed

ing

s o

f th

e S

oil

Scie

nce

So

cie

ty o

f A

me

rica

, V

ol. 3

7,

No

ve

mb

er-

De

ce

mb

er,

No

. 6

Ge

ne

ral

Info

rma

tio

n

Bra

nso

n,

R.L

. a

nd

Gu

sta

fso

n,

C.D

.1

97

2Ir

rig

atio

n W

ate

r -

A M

ajo

r S

alt C

on

trib

uto

r to

Avo

ca

do

Orc

ha

rds

Ca

lifo

rnia

Avo

ca

do

So

cie

ty Y

ea

rbo

ok

Ge

ne

ral

Info

rma

tio

n

Bro

uw

er,

R.

19

83

Fu

nctio

na

l E

qu

ilib

riu

m:

Se

nse

or

No

nse

nse

?N

eth

erla

nd

s J

ou

rna

l o

f A

gricu

ltu

ral S

cie

nce

. 3

1:3

35

-34

8

RD

D/0

4329

0001

(C

AH

2124

.xls

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age

9 of

12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Ge

ne

ral

Info

rma

tio

n

Ca

lifo

rnia

Ag

ricu

ltu

ral S

tatistics S

erv

ice

20

03

Ca

lifo

rnia

Ag

ricu

ltu

ral O

ve

rvie

wC

alif

orn

ia A

gricu

ltu

ral S

tatistics S

erv

ice

Ge

ne

ral

Info

rma

tio

n

Ca

lifo

rnia

Fe

rtili

ze

r A

sso

cia

tio

n1

98

5W

este

rn F

ert

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r H

an

db

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kF

ert

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r A

sso

cia

tio

n S

oil

Imp

rove

me

nt

Co

mm

itte

e,

Ca

lifo

rnia

Ge

ne

ral

Info

rma

tio

n

Ca

rma

n,

H.

20

03

Urb

an

Fa

rme

rs:

A P

rofile

of

the

Ca

lifo

rnia

Nu

rse

ry a

nd

Flo

ral In

du

str

y

Gia

nn

ini F

ou

nd

atio

n o

f A

gricu

ltu

ral E

co

no

mic

s

Ge

ne

ral

Info

rma

tio

n

Ch

ap

ma

n,

H.D

., E

dito

r1

96

6D

iag

no

stic C

rite

ria

fo

r P

lan

ts a

nd

So

ilsU

niv

ers

ity o

f C

alif

orn

ia D

ivis

ion

of

Ag

ricu

ltu

ral S

cie

nce

s

Ge

ne

ral

Info

rma

tio

n

Ch

ilde

rs,

No

rma

n F

., E

dito

r 2

00

3T

he

Str

aw

be

rry

Ge

ne

ral

Info

rma

tio

n

Ch

ristia

nse

n,

J.E

., O

lse

n,

E.C

., W

illa

rdso

n,

L.S

.

19

77

Irrig

atio

n W

ate

r Q

ua

lity E

va

lua

tio

nJo

urn

al o

f th

e I

rrig

atio

n a

nd

Dra

ina

ge

Div

isio

n

Ge

ne

ral

Info

rma

tio

n

Co

un

ty S

an

ita

tio

n D

istr

icts

of

Lo

s A

ng

ele

s

Co

un

ty

19

99

Fin

al D

raft

Sa

nta

Cla

ra R

ive

r W

ate

rsh

ed

Ch

lorid

e

Stu

dy

Sa

me

as a

uth

or

Ge

ne

ral

Info

rma

tio

n

Cra

m,

W.J

.1

97

3In

tern

al F

acto

rs R

eg

ula

tin

g N

itra

te a

nd

Ch

lorid

e I

nflu

x

in P

lan

t C

ells

Jo

urn

al o

f E

xp

erim

en

tal B

oto

ny 2

4(2

7):

32

8-3

41

Ge

ne

ral

Info

rma

tio

n

Ea

ton

, F

.M.,

McC

allu

m,

R.D

., a

nd

Ma

yh

ug

h,

M.

19

41

Qu

alit

y o

f Ir

rig

atio

n W

ate

rs o

f th

e H

olli

ste

r A

rea

of

Ca

lifo

rnia

With

Sp

ecia

l R

efe

ren

ce

to

Bo

ron

Co

nte

nt

an

d I

ts E

ffe

ct

on

Ap

rico

ts a

nd

Pru

ne

s

U.S

. D

ep

art

me

nt

of

Ag

ricu

ltu

re,

Wa

sh

ing

ton

, D

.C.,

Te

ch

nic

al

Bu

lletin

No

. 7

46

Ge

ne

ral

Info

rma

tio

n

El-M

ota

ium

, F

., H

u,

N.,

an

d B

row

n,

P.

19

94

Th

e R

ela

tive

To

lera

nce

of

Six

Pru

nu

s R

oo

tsto

cks t

o

Bo

ron

an

d S

alin

ity

Am

erica

n S

ocie

ty f

or

Ho

rtic

ultu

ral S

cie

nce

11

9(6

):1

16

9-1

17

5.

Ge

ne

ral

Info

rma

tio

n

Esm

el, C

., D

uva

l, R

.2

00

3S

up

ple

me

nta

l C

alc

ium

as a

Me

an

s t

o I

ncre

ase

Sh

elf

Life

of

Str

aw

be

rry

Be

rry T

ime

s,

Un

ive

rsity o

f F

lorid

a E

xte

nsio

n,

Vo

l. 3

(2

)

Ge

ne

ral

Info

rma

tio

n

Fa

be

r, D

r. B

.1

99

7C

hlo

rid

e a

nd

Sa

linity E

ffe

cts

on

Ag

ricu

ltu

reU

niv

ers

ity o

f C

alif

orn

ia C

oo

pe

rative

Exte

nsio

n.

Ve

ntu

ra C

ou

nty

Fa

rm A

dvis

or's O

ffic

e

Ge

ne

ral

Info

rma

tio

n

Fe

igin

, A

.1

98

5F

ert

iliza

tio

n M

an

ag

em

en

t o

f C

rop

s I

rrig

ate

d w

ith

Sa

line

Wa

ter

Pla

nt

an

d S

oil

89

:28

5-2

99

Ge

ne

ral

Info

rma

tio

n

Fip

ps,

G.

No

ne

Irrig

atio

n W

ate

r Q

ua

lity S

tan

da

rds a

nd

Sa

linity

Ma

na

ge

me

nt

Te

xa

s A

gricu

ltu

ral E

xte

nsio

n S

erv

ice

B-1

66

7

Ge

ne

ral

Info

rma

tio

n

Fru

it G

row

ers

La

bo

rato

ry,

Inc.

No

ne

Wa

ter

Cla

ssific

atio

n S

ch

em

es in

Ge

ne

ral U

se

Th

rou

gh

ou

t th

e U

nite

d S

tate

s

Un

kn

ow

n

Ge

ne

ral

Info

rma

tio

n

Gra

tta

n,

S.

19

93

Ho

w P

lan

ts R

esp

on

d t

o S

alts

Ag

ricu

ltu

ral S

alin

ity &

Dra

ina

ge

UC

Da

vis

Co

op

era

tive

Exte

nsio

n

(93

-03

)

Ge

ne

ral

Info

rma

tio

n

Gra

tta

n,

S.R

., O

ste

r, J

,2

00

2D

rou

gh

t T

ip 9

2-1

9 W

ate

r Q

ua

lity G

uid

elin

es f

or

Tre

es

an

d V

ine

s

Un

ive

rsity o

f C

alif

orn

ia,

Da

vis

.

Ge

ne

ral

Info

rma

tio

n

Gro

ss,

W.,

Lo

uie

, B

.2

00

0A

na

lysis

of

an

"Im

pa

irm

en

t" D

ete

rmin

atio

n D

ue

to

Ch

lorid

e in

th

e S

an

ta C

lara

Riv

er

Co

un

ty S

an

ita

tio

n D

istr

icts

of

Lo

s A

ng

ele

s C

ou

nty

Ge

ne

ral

Info

rma

tio

n

Ho

ffm

an

, G

.J.,

Oste

r, J

.D.,

Ma

as,

E.V

.,

Rh

oa

de

s,

J

19

84

Min

imiz

ing

Sa

lt in

Dra

in W

ate

r b

y I

rrig

atio

n

Ma

na

ge

me

nt

- A

rizo

na

Fie

ld S

tud

ies w

ith

Citru

s

Ag

ricu

ltu

ral W

ate

r M

an

ag

em

en

t, 8

, 6

1-7

8 E

lievie

r S

cie

nce

Pu

blis

he

rs B

.V.,

Am

ste

rda

m -

Prin

ted

in

th

e N

eth

erla

nd

s

Ge

ne

ral

Info

rma

tio

n

Irvin

e R

an

ch

Wa

ter

Dis

tric

t1

99

41

99

3 R

ecla

ime

d W

ate

r A

nn

ua

l R

ep

ort

Sa

me

as a

uth

or

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

10 o

f 12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Ge

ne

ral

Info

rma

tio

n

Irvin

e R

an

ch

Wa

ter

Dis

tric

t1

99

4R

ecla

ime

d W

ate

r A

nn

ua

l R

ep

ort

Sa

me

as a

uth

or

Vo

l. 2

Ge

ne

ral

Info

rma

tio

n

Irvin

e R

an

ch

Wa

ter

Dis

tric

t1

99

7R

ecla

ime

d W

ate

r Q

ua

lity R

ep

ort

Sa

me

as a

uth

or

Vo

l. 2

Ge

ne

ral

Info

rma

tio

n

Ke

lley,

W.P

., E

sq

.1

94

0P

erm

issib

le C

om

po

sitio

n a

nd

Co

nce

ntr

atio

n o

f Ir

rig

atio

n

Wa

ter

Am

erica

n S

ocie

ty o

f C

ivil

En

gin

ee

rs T

ran

sa

ctio

ns P

ap

er

No

.

21

14

Ge

ne

ral

Info

rma

tio

n

La

ng

, A

. 1

96

7O

sm

otic C

oe

ffic

ien

ts a

nd

Wa

ter

Po

ten

tia

ls o

f S

od

ium

Ch

lorid

e S

olu

tio

ns f

rom

0 t

o 4

0 C

Au

str

alia

n J

ou

rna

l o

f C

he

mis

try 2

0:

20

17

-20

23

Ge

ne

ral

Info

rma

tio

n

La

ntz

ke

, N

., C

ald

er,

T.

19

99

Wa

ter

Sa

linity a

nd

Cro

p I

rrig

atio

nF

arm

no

te 4

6/9

9 A

gricu

ltu

re W

este

rn A

ustr

alia

Ge

ne

ral

Info

rma

tio

n

La

ntz

ke

, N

., C

ald

er,

T.

20

04

Wa

ter

Sa

linity a

nd

Cro

p I

rrig

atio

nD

ep

art

me

nt

of

Ag

ricu

ltu

re F

arm

no

te N

o.

34

/20

04

Re

pla

ce

s 4

6/9

9

Ge

ne

ral

Info

rma

tio

n

Le

tey,

J.

an

d D

ina

r, A

.1

98

6S

imu

late

d C

rop

-Wa

ter

Pro

du

ctio

n F

un

ctio

ns f

or

Se

ve

ral

Cro

ps W

he

n I

rrig

ate

d w

ith

Sa

line

Wa

ters

Hilg

ard

ia,

Vo

lum

e 5

4,

No

. 1

Ge

ne

ral

Info

rma

tio

n

Lu

nin

, J.

19

67

Wa

ter

for

Su

pp

lem

en

tal Ir

rig

atio

nW

ate

r Q

ua

lity C

rite

ria

, A

ST

M S

TP

41

6.

p 6

6.

Ge

ne

ral

Info

rma

tio

n

Ma

as,

E.V

.1

98

4S

alt T

ole

ran

ce

of

Pla

nts

In H

an

db

oo

k o

f P

lan

t S

cie

nce

in

Ag

ricu

ltu

re.

B.R

. C

hristie

(e

d.)

.

CR

C P

ress,

Bo

ca

Ra

ton

, F

lorid

a

Ge

ne

ral

Info

rma

tio

n

Ma

as,

E.V

.1

98

5C

rop

To

lera

nce

to

Sa

line

Sp

rin

klin

g W

ate

rP

lan

t a

nd

So

il 8

9:

27

3-2

84

Ge

ne

ral

Info

rma

tio

n

Ma

as,

E.V

.1

98

7S

alt T

ole

ran

ce

of

Pla

nts

In H

an

db

oo

k o

f P

lan

t S

cie

nce

in

Ag

ricu

ltu

re.

(ed

.) B

.R.

Ch

ristie

-

CR

C P

ress I

nc.,

Vo

l. I

I, p

. 5

7-7

5

Ge

ne

ral

Info

rma

tio

n

Ma

as,

E.V

.1

98

6S

alt T

ole

ran

ce

of

Pla

nts

Ap

plie

d A

gricu

ltu

ral R

ese

arc

h V

ol. 1

, N

o.

1,

p 1

2-2

6

Ge

ne

ral

Info

rma

tio

n

Ma

as,

E.V

.1

99

0C

rop

Sa

lt T

ole

ran

ce

Ag

ricu

ltu

ral S

alin

ity A

sse

ssm

en

t, C

ha

pte

r 1

3:2

62

-30

4

Ge

ne

ral

Info

rma

tio

n

Ma

as,

E.V

. a

nd

Ho

ffm

an

, G

.J.

19

77

Cro

p S

alt T

ole

ran

ce

- C

urr

en

t A

sse

ssm

en

tJo

urn

al o

f th

e I

rrig

atio

n a

nd

Dra

ina

ge

Div

isio

n.

Pro

ce

ed

ing

s o

f

the

Am

erica

n S

ocie

ty o

f C

ivil

En

gin

ee

rs.

Vo

l. 1

03

, N

o.

IR2

Ge

ne

ral

Info

rma

tio

n

Ma

rga

ritz

, M

. a

nd

Na

dle

r, A

.1

99

3A

gro

tech

nic

ally

In

du

ce

d S

alin

iza

tio

n in

th

e U

nsa

tura

ted

Zo

ne

of

Lo

essia

l S

oils

, N

.W.

Ne

ge

v,

Isra

el

De

pt.

of

En

viro

nm

en

tal S

cie

nce

s a

nd

En

erg

y R

ese

arc

h,

Th

e

We

izm

an

n I

nstitu

te o

f S

cie

nce

, R

eh

ovo

t, 7

61

00

, Is

rae

l

Ge

ne

ral

Info

rma

tio

n

McK

ee

, J.E

an

d W

olf,

H.W

., E

dito

rs1

96

3W

ate

r Q

ua

lity C

rite

ria

, S

eco

nd

Ed

itio

nT

he

Re

so

urc

es A

ge

ncy o

f C

alif

orn

ia,

Sta

te W

ate

r Q

ua

lity C

on

tro

l

Bo

ard

, P

ub

lica

tio

n N

o.

3-A

Ge

ne

ral

Info

rma

tio

n

McK

ee

, J.E

. a

nd

Wo

lf,

H.W

., E

dito

rs1

96

3W

ate

r Q

ua

lity C

rite

ria

, S

eco

nd

Ed

itio

n R

evis

ed

Th

e R

eso

urc

es A

ge

ncy o

f C

alif

orn

ia,

Sta

te W

ate

r R

eso

urc

es

Co

ntr

ol B

oa

rd,

Pu

blic

atio

n N

o.

3-A

Ge

ne

ral

Info

rma

tio

n

Mo

tze

r, W

.E.,

Prie

sta

f, I

.2

00

3H

yd

rog

eo

lic A

sse

ssm

en

t fo

r th

e A

dm

inis

tra

tive

Dra

ft

En

viro

nm

en

tal Im

pa

ct

Re

po

rt (

AD

EIR

) fo

r th

e A

lam

ed

a

Co

un

ty R

eso

urc

e C

on

se

rva

tio

n a

nd

Op

en

Sp

ace

(RO

SA

) N

ort

h L

ive

rmo

re I

nte

nsiv

e A

gricu

ltu

re (

NL

IA)

Pro

gra

m

To

dd

En

gin

ee

rs T

ech

nic

al M

em

ora

nd

um

to

Sco

tt G

reg

ory

,

La

mp

hie

r-G

reg

ory

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

11 o

f 12

Bib

liog

rap

hy

Tab

le Cro

pA

uth

or

Ye

ar

Tit

leS

ou

rce

Ge

ne

ral

Info

rma

tio

n

Mu

nn

s,

R.

an

d P

assio

ura

, J.B

.1

98

4E

ffe

ct

of

Pro

lon

ge

d E

xp

osu

re t

o N

aC

l o

n t

he

Osm

otic

Pre

ssu

re o

f L

ea

f X

yle

m S

ap

fro

m I

nta

ct,

Tra

nsp

irin

g

Ba

rle

y P

lan

ts

Au

str

alia

n J

ou

rna

l o

f P

lan

t P

hysio

log

y,

II,

49

7-5

07

Ge

ne

ral

Info

rma

tio

n

Oste

r, J

.D.

20

02

To

tal M

axim

um

Da

ily L

oa

d f

or

Ch

lorid

e in

th

e U

pp

er

Sa

nta

Cla

ra R

ive

r

Co

mm

en

ts w

ritt

en

by J

.D.

Oste

r a

bo

ut

the

Au

gu

st

21

, 2

00

2,

Sta

ff

Re

po

rt e

ntitle

d T

ota

l M

axim

um

Da

ily L

oa

d f

or

Ch

lorid

e in

th

e

Up

pe

r S

an

ta C

lara

Riv

er.

U.S

. C

om

mitte

e o

n I

rrig

atio

n a

nd

Dra

ina

ge

, D

en

ve

r, C

olo

rad

o.

Pu

blis

he

d b

y C

alif

orn

ia R

WQ

CB

,

LA

Re

gio

n

Ge

ne

ral

Info

rma

tio

n

Oste

r, J

.D.

19

94

Irrig

atio

n w

ith

po

or

qu

alit

y w

ate

rA

gricu

ltu

ral W

ate

r M

an

ag

em

en

t 2

5:

27

1-2

97

Ge

ne

ral

Info

rma

tio

n

Oste

r, J

.D.,

Sh

ain

be

rg,

I.,

Ab

rol, I

.P.

19

96

Re

cla

ma

tio

n o

f S

alt-A

ffe

cte

d S

oil

Cb

. 1

4.

In:

M.

Ag

assi (e

d.)

. S

oil

Ero

sio

n,

Co

nse

rva

tio

n,

an

d

Re

ha

bili

tatio

n.

Ma

rce

l D

ekke

r, I

nc.

Ne

w Y

ork

. p

31

5-3

51

Ge

ne

ral

Info

rma

tio

n

Pitts

, D

., C

ap

ece

, J.

No

ne

Mic

ro I

rrig

atio

n M

an

ag

em

en

t W

ork

sh

op

Se

rie

s -

Irrig

atio

n W

ate

r Q

ua

lity f

or

Mic

ro I

rrig

atio

n S

yste

ms

Dra

ft M

icro

Irr

iga

tio

n M

an

ag

em

en

t W

ork

sh

op

Se

rie

s S

ou

thw

est

Flo

rid

a R

ese

arc

h a

nd

Ed

uca

tio

n C

en

ter

Un

ive

rsity o

f F

lorid

a

Le

sso

n P

lan

Mo

du

le N

o.

7

Ge

ne

ral

Info

rma

tio

n

Te

kin

el, O

., K

an

be

r, R

., D

ike

r, K

.2

00

2T

he

Po

ten

tia

l U

se

of

Drip

Irr

iga

tio

n S

yste

ms f

or

Su

sta

ina

ble

Ag

ricu

ltu

re U

nd

er

Sa

line

Wa

ter

an

d S

oil

Co

nd

itio

ns

KS

U J

ou

rna

l o

f S

cie

nce

an

d E

ng

ine

erin

g 5

(1):

1-1

8

Ge

ne

ral

Info

rma

tio

n

va

n S

ch

ilfg

aa

rde

, J.

19

94

Irrig

atio

n -

a b

lessin

g o

r a

cu

rse

Ag

ricu

ltu

ral W

ate

r M

an

ag

em

en

t 2

5.

20

3-2

19

Ge

ne

ral

Info

rma

tio

n

Zim

me

rma

n,

P.W

. a

nd

Be

rg,

R.O

.1

93

4E

ffe

cts

of

Ch

lorin

ate

d W

ate

r o

n L

an

d P

lan

ts,

Aq

ua

tic

Pla

nts

, a

nd

Go

ldfish

Co

ntr

ibu

tio

ns f

rom

Bo

yce

Th

om

pso

n I

nstitu

te.

Vo

l. 6

RD

D/0

4329

0001

(C

AH

2124

.xls

)P

age

12 o

f 12