Response of Blackberry Cultivars to FertilizerSource during Establishment in an OrganicFresh Market Production System

Javier Fernandez-Salvador1,3, Bernadine C. Strik1,4,5,

and David R. Bryla2

ADDITIONAL INDEX WORDS. Rubus, pelletized soy meal, processed poultry litter, fishemulsion hydrolysate, molasses, fruit quality, Brix, percent soluble solids

SUMMARY. Blackberry (Rubus ssp. Rubus) cultivars, three trailing types (Marion,Black Diamond, and Obsidian) and one semierect type (Triple Crown), werestudied for their response to different types of fertilizer from 2011–12, at a certifiedorganic, grower collaborator site located in Jefferson, OR. Plants were fertilized ata target rate of 50 lb/acre nitrogen (N) each spring using three different sources: 1)a liquid fish and molasses blend (4N–0P–1.7K); 2) pelletized soy (Glycine max)meal (8N–0.4P–1.7K); and 3) pelletized, processed poultry litter (4N–1.3P–2.5K).Plants were drip irrigated, and weeds were managed using a polypropylene,permeable landscape fabric (weed mat). Plant responses were greatly affected bycultivar, whereas the effects of fertilizer type were relatively minor. ‘Triple Crown’produced the greatest yield in both years, whereas ‘Black Diamond’ and ‘Marion’had the lowest yield in 2011 and 2012, respectively. ‘Triple Crown’ fruit had thehighest percent soluble solids and were the least firm in 2011, whereas ‘Marion’fruit were the least firm in 2012.Harvest date, within year, affected the fruit qualityvariables measured in all cultivars. Most soil nutrient levels were within therecommended range for all fertilizer treatments, except for boron (B), whichdeclined to deficient levels in the second year. Fertilizer type had no effect on soilnutrient levels other than fertilization with the fish and molasses blend productincreased soil potassium and sodium. Soil nutrient levels were affected by cultivarbut varied by year for many nutrients. Primocane leaf tissue nutrient concentrationswere above or within recommended standards for most nutrients, except formagnesium (Mg), calcium (Ca), and B, which, depending on the cultivar, werebelow standards.Over the 2-year study, the blackberry cultivars responded similarlyto the three types of organic fertilizer. However, the cost of N varied from $8.16/lbfor the liquid fish and molasses blend, $5.35/lb for the pelletized soy meal, and$2.54/lb for the pelletized, processed poultry litter. Supplemental fertilizationwith B, Mg, and Ca would be required with each fertilizer studied to maintainrecommended soil fertility levels.

Organic blackberry productionin the United States increasedfrom 180 acres in 2005 (Strik

et al., 2007), to 495 acres in 2008[U.S. Department of Agriculture(USDA), 2010]. West coast statesaccounted for 970 acres of certified

or fully converted organic blackberryand red raspberry (Rubus idaeus) in2007 (Granatstein et al., 2010). Sig-nificant expansion in organic plantingsis expected in the next 10 years asconsumer demand for organic prod-ucts increases and growers become

more interested in targeting higher-value niche markets [Organic TradeAssociation (OTA), 2013].

Guidelines for fertilizer and nu-trient management in organic black-berry production are presently limitedto overarching recommendations fornitrogen application rates and appro-priate soil pH (Kuepper et al., 2003),and do not address different sourcesof N fertilizer or possible responsedifferences among blackberry types[e.g., erect, semierect, and trailingtypes (Finn and Strik, 2014; Strikand Finn, 2012)].

The yield response of blackberryto increased rates of N fertilizer hasbeen variable, depending on soil fer-tility, rates of N fertilizer used, andplant cultivar or age (Archbold et al.,1989; Naraguma and Clark, 1998;Nelson and Martin, 1986). Recom-mended rates of N application inconventional plantings vary with ageand cultivar of blackberry grown,ranging from 25 to 70 lb/acre N(Bushway et al., 2008; Hart et al.,2006). In blackberry, primocane leafnutrient concentration levels are typ-ically used to adjust nutrient manage-ment programs (Hart et al., 2006).However, primocane leaf percent Nmay (Fernandez-Salvador et al.,2015a, 2015b; Harkins et al., 2013)or may not (Naraguma et al., 1999)differ among cultivars when grownunder the same management. Fertil-izer application is recommend forlate winter/spring (Bushway et al.,2008; Hart et al., 2006), as black-berry plants require available fertil-izer N for new primocane growth(Malik et al., 1991; Mohadjer et al.,2001; Naraguma et al., 1999).

The availability of fertilizer N de-pends on the fertilizer source (Gutseret al., 2005) and the method of appli-cation (Kowalenko et al., 2000; Strik,2008). The number of organicallyapproved N fertilizer sources for cane-berries (Rubus sp.) is increasing asgreater production of organic cropsleads to more demand. Types of ap-proved organic fertilizers include liq-uid products that are best appliedusing tank sprays (by hand to canopyor soil) or fertigation (diluted andapplied through drip irrigation sys-tems) or pelletized and granular prod-ucts for localized bed or broadcastapplication using mechanical fertilizerspreaders. Common liquid fertilizerswith N sources suitable for organic

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production include fish emulsionor hydrolysate, vegetable hydrolysate[e.g., corn (Zea mays) steep liquor],and molasses, whereas dry fertilizersinclude raw, composted, and processedanimal manures (or manure-derivedproducts), plant and animal by-products(e.g., plant-based meals such as soymeal and animal-based meals such asfeather meal), or mineralized mate-rials (e.g., sodium nitrate or bat andbird guano) [Organic Materials Re-view Institute (OMRI), 2013]. Theorganic fertilizer source (e.g., manure,other animal processing by-products,composts) affects N release rate, animportant factor to consider whenplanning nutrient management pro-grams and when targeting crop needs(Gutser et al., 2005). Growers shouldconsider the availability and cost (perpound of N applied) of the fertilizermaterial and whether the rate of Nrelease will likely match crop demand.For example, manure products areoften readily available and cost effec-tive, but have a slow N release rate,whereas liquid fish emulsion is moreexpensive to purchase, likely less ex-pensive to apply when the drip irriga-tion system is used and has a relativelyrapid N release rate (Gale et al.,2006). Crops grown in organic pro-duction systems may require fewerfertilizer inputs and still produce effi-cient growth and comparable yieldsto the same crop grown in conven-tional production (M€ader et al.,2002).

The objective of the presentstudy was to evaluate the impactof three organic fertilizer types, in-cluding pelletized, processed poultrylitter, pelletized soy meal, and a fishhydrolysate and emulsion blend withadded molasses, on yield and fruitquality of blackberry cultivars grown

in an organic production system ata grower collaborator site. Fourpopular blackberry cultivars, BlackDiamond, Marion, and Obsidiantrailing types and Triple Crownsemierect type, were chosen for thestudy. ‘Black Diamond’ (Finn et al.,2005a), a cultivar grown for processedand fresh markets, and ‘Marion’ (Finnet al., 1997), grown predominantly forthe processed market, account for>75% of the 7200 acres of blackberryproduced in Oregon in 2012 (USDA,2013). ‘Obsidian’ (Finn et al., 2005b)is the most widely grown trailingblackberry for fresh market in Oregonand is also grown in other productionregions. ‘Triple Crown’ (Gallettaet al., 1998) is a fresh market, semi-erect cultivar desired for its relativelylate fruiting season and good flavor.

Materials and methodsSTUDY SITE. The study was con-

ducted at a grower collaborator site inJefferson, OR [lat. 44�40#N, long.122�58#W, elevation 233 ft; USDAhardiness zone 8b, average annualextreme minimum temperature from15 to 20 �F (U.S. Department of theInterior, 2013)].

The study site area consisted ofthree soil series: 1) Camas (sandy-skeletal, mixed, mesic FluventicHaploxerolls) gravelly sandy loam,2) Cloquato (coarse-silty, mixed,superactive, mesic Cumulic UlticHaploxerolls) silt loam, and 3) New-berg (coarse-loamy, mixed, mesicFluvaquentic Endoaquoll) fine sandyloam, distributed through the black-berry study site. A split plot designwas used to account for these soiltype and other differences (see thesection Experimental Design). Before

planting blackberry, the site wasfarmed as a conventional grass seedcrop, growing bentgrass (Agrostis sp.)in rotation with other grass cropsincluding creeping red fescue (Festucarubra), and ryegrass (Loliumperenne).

SITE PREPARATION. In Sept.2009, the farm was transitioned toorganic production and the plantingsite was prepared by: 1) mowing theremnant grass seed crop; 2) subsoil-ing to a depth of 2 ft; 3) disking,harrowing, and rolling; and 4) bedshaping (8 inches high, 2 ft wide atthe top, 3 ft wide at the base). Lime(calcium carbonate) was applied andincorporated at a rate of 444 lb/acrebefore bed shaping.

The grower divided the plantingarea into two 100 · 100-ft blockswith rows orientated in a north–southdirection. The planting was establishedas a grower guided on-farm cultivartrial using common organic commer-cial practices (0.46 total planted acres).

Drip irrigation [one line of driptubing (model UNIRAM; NetafimUSA, Fresno, CA) with 0.42-gal/hin-line, pressure-compensating emit-ters spaced every 18 inches] was in-stalled in the center of each row ontop of the raised bed. The raised bedswere then covered with a 6-ft-widepolypropylene woven 3.2-oz/yard2

geotextile cloth [‘‘weed mat’’ (modelTerraTexWoven; Hanes GeoCompo-nents, Winston-Salem, NC)], whichwas centered and secured on the bedusing 6-inch-long landscaping staples.Based on grower commercial manage-ment practices, the weed mat was cutat the center of the raised bed, to allowfor it to be opened for fertilizer appli-cations; the edges of the weed mat

UnitsTo convert U.S. to SI,multiply by U.S. unit SI unit

To convert SI to U.S.,multiply by

0.4047 acre(s) ha 2.47110.3048 ft m 3.28080.0929 ft2 m2 10.76393.7854 gal L 0.26422.54 inch(es) cm 0.39370.4536 lb kg 2.20461.1209 lb/acre kg�ha–1 0.89224.4482 lbf N 0.2248

28.3495 oz g 0.035370.0532 oz/acre g�ha–1 0.0143

305.1517 oz/ft2 g�m–2 0.003333.9057 oz/yard2 g�m–2 0.02951 ppm mg�kg–1 11 ppm mg�L–1 12.2417 ton(s)/acre Mg�ha–1 0.4461(�F – 32) O 1.8 �F �C (�C · 1.8) + 32

We appreciate research funding support provided bythe Northwest Center for Small Fruits Research, theUnited States Department of Agriculture NationalInstitute of Food and Agriculture (Formula Grant no.OREI 2010-01940; ORE00409), our industry con-tributors and collaborators, especially Eric Pond atRiverbend Farms, and the assistance provided by GilBuller and Emily Vollmer.

1Department of Horticulture, College of AgriculturalSciences, 4017 Agricultural and Life Science Building,Oregon State University, Corvallis, OR 97331

2U.S. Department of Agriculture, Agricultural Re-search Service, 3420 Northwest Orchard Avenue,Corvallis, OR 97330

3From the M.S. thesis of J. Fernandez-Salvador.

4Professor.

5Corresponding author. E-mail: Bernadine.strik@oregonstate.edu.

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were patched with smaller sections ofgeotextile fabric and held in place bylandscape staples. Weed mat was cho-sen as the in-row weed managementstrategy.

The area between rows (aisles)was seeded with 50 lb/acre fine fes-cue [a mixture of blue fescue (Festucalongifolia), chewings fescue (F. rubrassp. commutata), red fescue (F. rubrassp. rubra), slender creeping red fes-cue (F. rubra ssp. litoralis), and sheepfescue (F. ovina), cultivars unknown]following the USDA—Natural Re-sources Conservation Service recom-mendation for direct drill seedingspecies byHoag et al. (2011) (Brillionmodel Sure Stand seeder; LandollCorp., Brillion, WI).

PLANTING ESTABLISHMENT AND

MANAGEMENT. ‘Marion’, ‘Obsidian’,and ‘Triple Crown’ were obtained asrooted cuttings and ‘Black Diamond’as tissue-cultured, plug stock in Mayand July 2009, respectively. All plantswere potted into 1-gal pots andgrown at the farm until planting inOct. 2009 (north block) and May–June 2010 (south block), due tolabor availability and winter weatherconditions at the time of the firstplanting. Plant spacing varied betweencultivars/blocks ranging from 3.0to 4.5 ft in the row depending oncultivar vigor with 11 ft betweenrows (880–1320 plants/acre). In-rowplant spacing was 3.0 and 4.5 ft inthe north block and south block, re-spectively. A three-wire, vertical trelliswas installed soon after planting withthe lower trellis wire attached to steelposts at 2 ft above the top of the raisedbed, the middle wire at 4 ft, and theupper wire at 6 ft. The trellis used for‘Triple Crown’ had an additional 2-ftsteel cross arm bolted to each postwith a wire attached to each end of the‘‘T.’’ The posts in the rowwere spacedat 25 ft.

In 2010, all plants were fertilizedon 21 May and 3 Sept. with thefollowing: a) fish hydrolysate andemulsion blend with added molasses[3N–0.4P–0.8K, 2.7 lb/acre N perapplication (TRUE 315; True Or-ganics, Spreckels, CA)], b) 2.3 lb/acrecopper (Cu) as copper hydroxide, andc) 2.0 lb/acre zinc (Zn) as zinc sulfate.In 2010, the first growing season,primocanes were trained and tied tothe trellis as they grew per standardcommercial practice (Strik and Finn,2012). Once the primocanes grew

above the upper trellis wire, all thecanes were looped in one direction(south). In 2011 and 2012 (the firstand second fruiting seasons), the flo-ricanes (previous year’s primocanes)were hand-harvested and newly grow-ing primocanes were trained to thelowest trellis wire during the fruitingseason (for trailing cultivars). Afterfruit harvest, the dying floricanes wereremoved from each plant by pruning atcrown height and then were flailedmowed (chopped) in the aisles (modelSPF flail; RearsManufacturing, Eugene,OR) during the fall and winter. Inthe trailing cultivars, primocaneswere trained from August to Septem-ber by looping half the canes in eachdirection down to the lower trellis wireand bringing them back toward theplant with one or two twists (Strik andFinn, 2012). In ‘Triple Crown’, oncethe dying floricanes were removed, thegrower thinned the primocanes to twoto three canes per plant and placed thecanes between the cross-arm wires.The primocanes were topped at 5 to6 ft to control plant height. As ‘TripleCrown’ primocanes tend to branch atthe apical section of the cane duringthe growing season (3–5 ft height), thelong branches remaining after toppingwere trained and tied in a circularpattern to each side of the plant. Thefield was managed following NationalOrganic Program practices for cropproduction (USDA, 2011) from es-tablishment through the study periodand was first certified as organic in2012 (California Certified OrganicFarmers, Santa Cruz, CA) after thetransition periodwas completed. Plantswere irrigated typically in sets of 3 to4 h, four times per week from Junethrough September, or as requiredbased on grower experience and visualobservation of soil moisture status.

Pest management was per stan-dard commercial practice with a dor-mant application of agricultural sulfurto the canopy to manage cane diseasein Dec. 2011 (REX lime sulfur;ORCAL, Junction City, OR) at a rateof 2.4 gal per 100 gal of water. In2011 and 2012, the fungicides hay orgrass bacillus [Bacillus subtilis (Sere-nade� MAX; AgraQuest, Davis, CA)and root streptomyces [Streptomyceslydicus (Actinovate� AG; Natural In-dustries, Houston, TX)] were appliedin midspring (2011) or early and late-spring (2012) to help control graymold (Botrytis cinerea), per label rate

and recommendations. A spinosad(metabolites of Saccharopolyspora spi-nosa) insecticide (Entrust� SC; DowAgro Science, Indianapolis, IN) wasapplied to the field twice in eachseason to control the adults of spottedwing drosophila (Drosophila suzukii),per label rate and recommendations.

Weather data (total daily precip-itation and maximum and minimumdaily air temperature) were obtainedfrom 1 June to the end of harvest on30 Sept. 2011 and 2012 from theclosest available Pacific northwesternU.S. Cooperative AgriculturalWeatherNetwork AgriMet (U.S. Departmentof the Interior, 2013) weather stationlocated at Oregon State University’sHyslop Field Laboratory, Corvallis,OR.

EXPERIMENTAL DESIGN. Ourstudy was conducted in 2011 and2012, the first and second fruitingyears, respectively. Treatments werearranged in a split-plot design withthree replicates and included fourcultivars (Obsidan, Black Diamond,Marion, and Triple Crown) as mainplots and three fertilizer types [pellet-ized, processed poultry litter (poul-try), pelletized soy meal (soy), and afish hydrolysate and emulsion blendwith added molasses (fish)] as sub-plots. Each plot was 17 ft in lengthwith the exception of two plots on thesouth block that were 14 ft in length;these plot size differences wereaccounted for in all calculations.

The three fertilizer treatmentswere applied at an equivalent targetrate of N (50 lb/acre), based on thepercent N in the product as stated onthe label in both years of the study. Allfertilizers were applied under theweed mat (by opening, applying theproduct, and then reclosing the weedmat). The fish fertilizer used wasa blend of fish hydrolysate and fishemulsion with added molasses [4N–0P–1.7K (TRUE 402, True Or-ganics)] and was diluted with 10 partswater (v/v) and applied by hand,using a backpack sprayer, to the in-row area around and between plantsin four applications (30 Apr., 7 and18 May, and 1 June 2011; 27 Apr.,12 and 22 May, and 3 June 2012).Pelletized soy meal [8N–0.4P–1.7K(Phyta-Grow� Leafy Green Special�;California Organic Fertilizers, Han-ford, CA)] was broadcast in the rowarea on 30 Apr. 2011 and 26 Apr.2012. Pelletized, processed poultry

• June 2015 25(3) 279

litter [4N–1.3P–2.5K–7Ca (Nutri-Rich; Stutzman Environmental Prod-ucts, Canby, OR)] was broadcast inthe row area on 30 Apr. 2011 and 26Apr. 2012. The fertilizers studiedwere analyzed for total nutrient con-tent (Brookside Laboratories, NewBremen, OH), and the rate of allmacro- and micronutrients appliedwas calculated.

FRUIT HARVEST. Fruit werehand-harvested about twice weekly,per the grower’s schedule, selectingfruit that were toward the end of theshiny black stage. Harvested fruitwere separated into marketable (forfreshmarket) andunmarketable (‘‘cull’’;including overripe, sunburned, rotten,dropped, or otherwise damaged fruit)and total yield/plot calculated. Fruitingseason (first to last fruit harvest date)was recorded. A 25-berry subsampleper harvest date was used to determineaverage fruit quality variables, includingfruit weight (seasonal, weighted averagewas calculated), fruit firmness, andpercent soluble solids. The 25-berrysample was picked first, before the restof the plot, randomly selecting fruitfrom both sides of the row and cov-ering the entire length of the plotarea. Fruit firmness of each berry wasmeasured using a University of Cal-ifornia Manual Firmness Tester (serialNo. 364; Western Industrial Supply,San Francisco, CA) with a mechanicalforce gauge (model LKG1; Ametek,Feasterville, PA)with a0.5-inch-diametertip. Each berry was laid on its side andforce was applied until the first drop ofjuice cameout of oneormore drupelets.The fruit were then placed in a 1/4-galpolyethylene resealable bag andcrushed by hand to obtain a homo-geneous mixture for measuringpercent soluble solids, on a tempera-ture-compensated digital refractom-eter (Atago, Bellevue, WA).

LEAF TISSUE AND NUTRIENT

CONCENTRATION. Primocane leaveswere sampled on 3 Aug. 2012, perstandard recommended practice (Hartet al., 2006). Samples per plot con-sisted of 10 of the most recent fullyexpanded primocane leaves, selectedfrom both sides of the row and weresent to Brookside Laboratories foranalysis of leaf tissue N, phosphorus(P), potassium (K), Mg, Ca, sulfur (S),B, iron (Fe),manganese (Mn), Cu,Zn,and aluminum (Al) concentration. To-tal leafNwas determined by a combus-tion analyzer using an induction

furnace and a thermal conductivitydetector (Gavlak et al., 1994). Allother nutrient concentrations weredetermined via inductively coupledplasma spectrophotometer (ICP) af-ter wet washing in nitric/perchloricacid (Gavlak et al., 1994). Nutrientconcentrations in the primocaneleaves were compared with publishedstandards (Hart et al., 2006).

SOIL SAMPL ING AND SOIL

NUTRIENT CONTENT. Soil samples werecollected on 3 Nov. 2011 and 5 Nov.2012, using a 15/16-inch-diameter,21-inch-long, slotted, open-side,chrome-plated steel soil probe (SoilSampler model Hoffer; JBK Manu-facturing, Dayton, OH). One samplewas collected per treatment plot. Eachsample was composed of four corescollected to a depth of 12 inches fromthe top of the raised bed (two fromeachside of the center plant and two fromthe inner side of the border plants); allcores were within the irrigation emitterdrip zone of the in-row area.

All soil samples were sent foranalysis to Brookside Laboratories andextractable soil P (Bray 1 extraction),K, Ca, Mg, sulphate–sulfur (SO4–S),sodium (Na), B, Cu, Mn, and Zn weredetermined by ICP, after extractionof the nutrients using the Mehlich3 method (Mehlich, 1984). Soil nitrate-nitrogen (NO3-N) and ammonium-nitrogen (NH4-N) were determinedusing automated colorimetric methodsafter extraction with 1 M potassiumchloride [KCl (Dahnke, 1990)]. Soilorganic matter was measured usingloss-on-ignition at 360 �C (Nelsonand Sommers, 1996) and soil pHusing the 1:1 soil:water method(McLean, 1982).

DATA ANALYSIS. Data were ana-lyzed for a split-split-plot design us-ing year as a main plot factor, cultivaras a subplot, and fertilizer type asa sub-subplot. Due to significant yeareffects and plants maturing duringthe study period, data were reana-lyzed by year as a split-plot (cultivaras main plot and fertilizer as subplot)using the General Linear Model pro-cedure in SAS (version 9.3; SAS In-stitute, Cary, NC). Data were testedfor normality and log transformed, ifneeded to meet criteria for normalityand homogeneity of variance. Meanswere compared for treatment effectsusing a Fisher’s protected least signif-icant difference (LSD) with a = 0.05.Comparison within interactions were

analyzed for treatment effects usinga least square means (LS Means) witha = 0.05. The effect of harvest date onyield and fruit quality was analyzed bycultivar using a split-split-plot designwith year as the main plot, fertilizer asthe subplot, and harvest date as a thesub-subplot factor.

ResultsWhen the data were analyzed as

a split-split-plot with year as the mainplot factor, year had a significanteffect on fruit weight (P = 0.02),fruit firmness (P < 0.0001), totalyield (P < 0.0001), and marketableyield (P = 0.001). There was a signif-icant year · cultivar interaction forfruit weight (P < 0.0001), fruit firm-ness (P < 0.0001), percent solublesolids (P = 0.03), and total yield (P =0.03). Data for seasonal total andmarketable yield and fruit quality vari-ables were then analyzed and are pre-sented by year (Table 1).

FERTILIZER TYPE. There was nosignificant main effect of fertilizertype on yield (marketable and total)or fruit quality in 2011 or 2012.However, there was a significant fer-tilizer · cultivar interaction on fruitweight in 2011, total yield in 2011and 2012, and marketable yield in2012 (Table 1).

The effects of fertilizer type ontotal yield varied with cultivar, butresults were inconsistent among thetwo years (Table 1). ‘Triple Crown’produced a higher total yield in 2011when fertilized with soy than withpoultry, but there was little fertilizereffect on total yield of this cultivar in2012 or for all other cultivars in 2011and 2012. Fertilizer type had no effecton marketable yield in 2011, but in2012 ‘Obsidian’ had a greater market-able yield when fertilized with soy ascomparedwith fish. In 2011, there wasno effect of fertilizer on fruit weightin ‘Triple Crown’ and ‘Obsidian’,whereas ‘Black Diamond’ tended tohave the greatest fruit weight whenfertilized with poultry or fish and‘Marion’ when fertilized with poultry(Table 1). There was no effect offertilizer on berry weight in 2012 orpercent soluble solids and firmness ineither year (Table 1).

The fertilizers applied in 2011and 2012, came from the same batch.The calculated rate of all nutrientsapplied is shown (Table 2) for 2012only, as the laboratory results for the

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samples sent in 2011 and 2012, werevery similar. Although the amount ofproduct to apply for each fertilizerwas calculated based on the percent-age of N, as stated on the label, andthe target rate of N (50 lb/acre), theactual rate of N applied was 47, 45,and 44 lb/acre for the poultry, fish,and soy products, respectively (Ta-ble 2). Poultry litter contained morethan 70-fold the Ca, 4-fold the P,and more than 3-fold the Mg, Fe,

Mn, and Zn than the fish and soyfertilizers. The fish fertilizer con-tained 4- to 20-fold the Na as thepoultry and soy fertilizer sources,respectively. Fertilization with fishalso led to higher rates of K appliedthan when poultry and soy were used(Table 2).

Soil pH was at the upper end ofthe recommended range for black-berry (5.6 to 6.5) (Hart et al., 2006)for all treatments in 2011, but by

2012, the pH had declined to thelower end of the range (Table 3). Thesoil organic matter content was un-affected by fertilizer type and wouldbe considered high for typical black-berry fields in Oregon.

Most of the nutrient levels inthe soil were within or above therecommended range for caneberriesin Oregon (Hart et al., 2006) for allfertilizer treatments. Soil P, K, Ca,and Mg were considerably above

Table 1. Effect of cultivar and fertilizer type on fruit weight, percent soluble solids, fruit firmness, and total and marketablefruit yield in a new field of hand-picked organic blackberry at a grower collaborator site in Jefferson, OR during the first2 years after planting (2011–12) as determined by analysis of variance for a split-plot design (cultivar as main plots andfertilizer as subplots).

Treatments Fruit wt (g)zSolublesolids (%) Firmness (gf)z Total yield (Mg�haL1)z

Marketableyield (Mg�haL1)

Poultryy Fish Soy Poultry Fish Soy

Cultivar 2011Black Diamond 7.27 b x 7.03 b 6.70 bc 10.4 b 412 b 7.9 bc 7.1 bc 5.9 c 5.2 bMarion 5.90 cd 5.87 d 5.73 d 12.0 a 236 c 12.8 b 12.1 b 12.2 b 10.3 abObsidian 8.50 a 8.67 a 8.63 a 12.0 a 467 a 10.8 b 9.5 bc 11.8 b 5.9 bTriple Crown 8.43 a 8.83 a 9.20 a 12.4 a 208 d 13.8 b 15.9 ab 18.6 a 14.0 a

Significancew

Fertilizer (F) NS NS NS NS NS

Cultivar (C) <0.0001 <0.0001 <0.0001 <0.0001 <0.0001C · F 0.02 NS NS 0.04 NS

Poultry Fish Soy Poultry Fish Soy

Cultivar 2012Black Diamond 6.89 b 10.1 d 269 b 18.2 b 16.9 bc 16.2 bc 10.9 c 9.2 c 8.5 cMarion 5.43 c 12.7 b 176 d 12.3 c 15.6 bc 13.0 c 9.2 c 11.4 bc 10.2 cObsidian 7.02 b 11.8 c 329 a 15.5 bc 15.2 bc 19.8 b 11.3 bc 11.1 c 14.6 bTriple Crown 9.81 a 13.0 a 196 c 26.6 a 26.6 a 27.8 a 20.0 a 20.0 a 21.1 a

SignificanceFertilizer NS NS NS NS NS

Cultivar <0.0001 <0.0001 <0.0001 <0.0001 <0.0001C · F NS NS NS 0.009 0.0034

z1 g = 0.0353 oz, 1 g-force (gf) = 0.0098 N = 0.0022 lbf, 1 Mg�ha–1 = 0.4461 ton/acre.yFertilizer products used were pelletized, processed poultry litter [‘‘poultry,’’ 4N–1.3P–2.5K–7Ca (Nutri-Rich; Stutzman Environmental Products, Canby, OR)], a blend offish hydrolysate and fish emulsion with added molasses [‘‘fish,’’ 4N–0P–1.7K (TRUE 402; True Organic Products, Spreckels, CA)], and pelletized soy meal [‘‘soy,’’ 8N–0.4P–1.7K (Phyta Grow Leafy Green Special; California Organic Fertilizers, Hanford, CA)]. The three fertilizer treatments were applied at an equivalent total rate of N of 50 lb/acre(56.0 kg�ha–1) in 2011 and 2012, based on the percent nitrogen in the product as stated on the label.xMeans followed by the same letter within the treatment or the interaction were not significantly different via least square means at P > 0.05.wProbability value provided unless nonsignificant [NS (P > 0.05)].

Table 2. Total nutrients applied in a new field of hand-picked organic blackberry in 2012 at a grower collaborator site inJefferson, OR.

FertilizerzMacronutrients (lb/acre)y Micronutrients (oz/acre)y

Nx P K Ca Mg Na B Fe Mn Cu Zn Al

Poultry 47 28 32 144 9 5 1 13 9 1 8 6Soy 44 4 15 2 2 0 0 2 0 0 1 1Fish 47 7 56 1 1 23 0 5 0 0 1 3zFertilizers were analyzed by Brookside Laboratories, (New Bremen, OH). Pelletized, processed poultry litter [‘‘poultry,’’ 4N–1.3P–2.5K–7Ca (Nutri-Rich; StutzmanEnvironmental Products, Canby, OR)] was applied as a band application on top of the soil at the center of the raised bed in spring. Fish hydrolysate and fish emulsion withadded molasses mixture [‘‘fish,’’ 4N–0P–1.7K (TRUE 402; True Organic Products, Spreckels, CA)] was diluted with water (1:10, v/v) before application as a directed spray tothe bed surface in four equal portions in spring. Pelletized soymeal [‘‘soy,’’ 8N–0.4P–1.7K (Phyta Grow Leafy Green Special; California Organic Fertilizers, Hanford, CA)] wasapplied as a band on top of the soil in the center of the raised bed in spring. ‘‘Poultry’’ had a pH of 8.3, ‘‘fish’’ had a pH of 5.5, and ‘‘soy’’ had a pH of 6.2.y1 lb/acre = 1.1209 kg�ha–1, 1 oz/acre = 70.0532 g�ha–1.xN = nitrogen; P = phosphorus, K = potassium, Ca = calcium, Mg =magnesium, Na = sodium, B = boron, Fe = iron, Mn =manganese, Cu = copper, Zn = zinc, Al = aluminum.

• June 2015 25(3) 281

Tab

le3.Effectofcu

ltivar

andfertilizer

sourceonsoilpH,organ

icmatter,an

dnutrientco

ntentin

anew

fieldofhan

d-picked

organ

icblackberry

atagrower

collab

orator

site

inJefferson,O

Ron3Nov.2011an

d5Nov.2012as

determined

byan

alysisofvarian

ceforasplit-plotdesign[cultivar

asmainplotsan

dfertilizer

assubplots(n

=3)].

Treatmen

tspH

OM

z

(%)

NO

3–N

(ppm)y

NH

4–N

(ppm)

P(ppm)

KCa

Mg

Na

BFe

Mn

Cu

Zn

Al

(mg�kg

L1)

y

Poultry

xFish

Soy

Poultry

Fish

Soy

Poultry

Fish

Soy

Poultry

Fish

Soy

2011

Cultivar

Black

Diamond

6.4

4.7

6.82bcw

1.80

130

387

4,595a

4,422ab

4,038ab

785

60.7

d80.3

dc

55.7

d0.56c

340.0

20.3

b31.3

a23.0

ab5.00

7.50

1,103cd

1,098d

1,187abcd

Marion

6.3

4.1

13.19a

1.86

151

405

4,266ab

4,260ab

4,156ab

806

71.0

dc

99.7

bc

74.0

dc

0.76a

363.1

25.7

ab23.0

ab22.0

b5.10

6.70

1,248ab

1,272ab

1,220abc

Obsidian

6.2

4.2

9.41ab

2.39

157

496

4,398ab

3,833ab

4,308ab

785

77.7

dc

122.3

ab74.0

dc

0.71ab

370.6

22.3

b28.3

ab24.3

ab5.60

7.40

1,258ab

1,277a

1,194abcd

Triple

Crown

6.1

4.7

3.67c

1.17

125

430

3,721b

3,732b

4,332ab

735

71.3

dc

142.3

a71.0

dc

0.62bc

341.2

27.0

ab28.3

ab21.0

b4.10

5.70

1,119cd

1,160bcd

1,173abcd

Fertilizer

Poultry

6.3

4.3

8.19

1.70

139

398b

——

—761

——

—0.68

344.7

——

—4.80

6.90

——

—

Fish

6.1

4.5

9.55

2.40

148

551a

——

—758

——

—0.65

359.8

——

—4.80

6.50

——

—

Soy

6.3

4.4

7.08

1.40

135

339b

——

—815

——

—0.66

356.7

——

—5.20

7.10

——

—

Significance

v

Cultivar

(C)

NS

NS

0.048

NS

NS

NS

NS

NS

<0.0001

0.026

NS

NS

NS

NS

0.005

Fertilizer(F)

NS

NS

NS

NS

NS

<0.0001

NS

NS

0.004

NS

NS

0.0007

NS

NS

NS

C·F

NS

NS

NS

NS

NS

NS

0.009

NS

0.003

NS

NS

0.009

NS

NS

0.015

2012

Cultivar

Black

Diamond

5.6

4.7

17.9

a4.62

204

592

—3,655

—613

—71.6

—0.46

352

—27.3

—5.19

6.39

—1,138

—

Marion

5.7

4.7

10.4

b3.78

173

578

—3,376

—546

—68.1

—0.45

346

—25.6

—4.15

4.81

—1,096

—

Obsidian

5.7

4.8

10.4

b5.19

184

619

—3,342

—540

—77.3

—0.45

345

—28.0

—4.32

5.30

—1,087

—

Triple

Crown

5.9

4.6

10.5

b5.71

180

509

—3,588

—603

—73.7

—0.44

336

—26.8

—4.76

6.08

—1,047

—

Fertilizer

Poultry

5.8

4.6

12.7

4.60

192

532b

—3,534

—568

—60.7

b—

0.45

329.1

b—

25.6

—4.32

5.87

—1,051c

—

Fish

5.7

4.8

12.1

4.28

200

665a

—3,453

—571

—104.4

a—

0.45

348.4

a—

28.2

—4.97

6.19

—1,090b

—

Soy

5.6

4.7

12.1

5.60

164

527b

—3,483

—587

—52.9

b—

0.46

356.3

a—

27.0

—4.53

4.88

—1,135a

—

Significance

Cultivar

NS

NS

0.01

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

Fertilizer

NS

NS

NS

NS

NS

0.033

NS

NS

0.0001

NS

0.011

NS

NS

NS

0.0007

C·F

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

zOM

=organicmatter,NO

3-N

=nitrate

nitrogen

,NH

4-N

=am

monium

nitrogen

,P=phosphorus,K=potassium,Ca=calcium,Mg=magnesium,Na=sodium,B=boron,Fe=iron,Mn=manganese,

Cu=copper,Zn=zinc,Al=

aluminum.

y1ppm

=mg�L

–1,1mg�kg

–1=1ppm.

xFertilizerproductsusedwerepelletized,p

rocessed

poultry

litter

[‘‘poultry,’’4N–1

.3P–2

.5K–7

Ca(N

utri-Rich;Stutzman

Environmen

talP

roducts,Canby,OR)],a

blendoffish

hyd

rolysate

andfish

emulsionwithadded

molasses

[‘‘fish,’’

4N–0P–1

.7K(T

RUE402;TrueOrganicProducts,Spreckels,CA)],andpelletizedsoymeal[‘‘soy,’’8N–0

.4P–1

.7K(PhytaGrowLeafy

Green

Special;CaliforniaOrganicFertilizers,Hanford,CA)].Thethreefertilizer

treatm

entswere

applied

atan

equivalen

ttotalrate

ofnitrogen

of50lb/acre

(56.0

kg�ha

–1)in

2011and2012,based

onthepercentnitrogen

intheproduct

asstated

onthelabel.

wMeansfollowed

bythesameletter

within

thetreatm

entorinteractionorin

agiven

columnwerenotsignificantlydifferentvialeastsquaremeansat

P>0.05.

vProbabilityvalueprovided

unless

nonsignificant[N

S(P

>0.05)].

282 • June 2015 25(3)

RESEARCHREPORTS

recommended levels (P-Bray = 20 to40 ppm, K = 150 to 350 ppm, Ca =1000 ppm, Mg = 120 ppm) in bothyears (Table 3). Soil Mn was at thelower end of the recommended level(20 to 60 ppm) in both years. Soil Bwas within the recommended level in2011 (0.5 to 1.0 ppm), but declinedto just below the recommended levelin 2012 (Table 3).

Fertilizer type affected soil K in2011 and there was a fertilizer ·cultivar interaction on soil Ca, Na,Mn, and Al (Table 3). In 2012,fertilizer treatment affected soil K,Na, Fe, and Al. There was no effectof fertilizer on available soil NO3-Nand NH4-N in either year. Fertiliza-tion with fish increased soil K in bothyears compared with poultry and soy.In 2011, soil Ca was highest in ‘BlackDiamond’ plots when fertilized withpoultry, but was highest in ‘TripleCrown’ plots when fertilized with soy.In contrast, there was relatively littleeffect of fertilizer source on soil Ca in‘Marion’ and ‘Obsidian’ (Table 3).There was no effect of fertilizer onsoil Ca in 2012, nor was there anyeffect on soil Mg in either year. Fer-tilization with fish increased soil Nafor all cultivars in 2011 and 2012. In2011, soil in ‘Black Diamond’ plotsfertilized with fish had a higher levelof Mn than in ‘Black Diamond’ and‘Obsidian’ fertilized with poultry and‘Marion’ and ‘Triple Crown’ fertil-ized with soy. There was no fertilizereffect on soil Mn in 2012. The effectsof fertilizer on soil Fe and Al wereinconsistent among years (Table 3).

Fertilizer type did not signifi-cantly affect primocane tissue nutri-ent concentration in 2012 for any ofthe nutrients tested, but there wasa significant fertilizer · cultivar in-teraction on tissue P concentration(Table 4). Plants fertilized with poul-try, which was higher in P (Table 2),had higher levels of tissue P, especiallyin ‘Obsidian’. However, cultivar ef-fects on tissue P were larger thanfertilizer effects.

CULTIVAR EFFECTS. There wasa significant main effect of cultivaron yield and all fruit quality variablesin 2011 and 2012. Interactions ofcultivar and fertilizer are describedabove. ‘Triple Crown’, a semierectblackberry, had the greatest totaland marketable yield in both years.Within the trailing types, ‘Black Di-amond’ and ‘Marion’ had the lowest Tab

le4.Effectofcu

ltivar

andfertilizer

sourceonprimocaneleaf

tissuenutrientco

ncentrationin

anew

fieldofhan

d-picked

organ

icblackberry

atagrower

collab

orator

site

inJefferson,OR

on3Aug.2012as

determined

byan

alysisofvarian

ceforasplit-plotdesign[cultivar

asmainplots

andfertilizer

assubplots

(n=3)].

Treatmen

ts

Macronutrients

(%)

Micronutrients

(ppm)y

P

KCa

Mg

SN

zPoultry

xFish

Soy

Fe

BCu

Mn

Zn

Al

Cultivar

Black

Diamond

2.7

cw0.30d

0.31d

0.32d

1.4

c0.22c

0.25c

0.15c

91.6

b18.6

b8.6

c39.0

c28.5

c58.4

bMarion

3.0

b0.40bc

0.43b

0.41b

1.8

b0.26b

0.25c

0.16c

97.4

b18.0

b9.2

bc

64.0

b42.8

b77.3

bObsidian

3.7

a0.53a

0.49a

0.49a

2.1

a0.24bc

0.28b

0.20b

133.1

a23.2

a12.0

a64.2

b52.7

a84.3

bTripleCrown

3.1

b0.36cd

0.38bcd

0.36cd

1.4

c0.34a

0.33a

0.23a

150.8

a19.4

b9.8

b93.2

a49.9

a123.8

a

Significance

v

Cultivar

(C)

0.01

0.0001

0.0001

0.001

0.0001

0.0001

0.004

0.02

0.001

0.0001

0.0001

0.01

Fertilizer(F)

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

C·F

NS

0.04

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

zN

=nitrogen

,P=phosphorus,K=potassium,Ca=calcium,Mg=magnesium,Na=sodium,B=boron,Fe=iron,Mn=manganese,

Cu=copper,Zn=zinc,Al=aluminum.

y1ppm

=mg�L

–1.

xFertilizerproductsusedwerepelletized,p

rocessed

poultry

litter

[‘‘poultry,’’4N–1

.3P–2

.5K–7

Ca(N

utri-Rich;Stutzman

Environmen

talP

roducts,Canby,OR)],a

blendoffish

hyd

rolysate

andfish

emulsionwithadded

molasses

[‘‘fish,’’

4N–0

P–1

.7K(T

RUE402;TrueOrganicProducts,Spreckels,CA)],andpelletizedsoymeal[‘‘soy,’’8N–0

.4P–1

.7K(PhytaGrowLeafy

Green

Special;CaliforniaOrganicFertilizers,Hanford,CA)].Thethreefertilizer

treatm

entswere

applied

atan

equivalen

ttotalrate

ofnitrogen

of50lb/acre

(56.0

kg�ha

–1)in

2011and2012,based

onthepercentnitrogen

intheproduct

asstated

onthelabel.

wMeansfollowed

bythesameletter

within

thetreatm

entortheinteractionwerenotsignificantlydifferentvialeastsquaremeansat

P>0.05.

vProbabilityvalueprovided

unless

nonsignificant[N

S(P

>0.05)].

• June 2015 25(3) 283

yield in 2011 and 2012, respectively(Table 1). The proportion of non-marketable fruit varied among culti-vars and between years averaging 45%and 27% for ‘Obsidian’, 25% and 44%for ‘Black Diamond’, 17% and 25%for ‘Marion’, and 13% and 25% for‘Triple Crown’ in 2011 and 2012,respectively [29% and 32% for thetrailing cultivars, on average (datanot shown)]. ‘Obsidian’ producedthe most cull or nonmarketable fruit(4.8 Mg�ha–1) in 2011 and ‘BlackDiamond’ (7.6 Mg�ha–1) in 2012(data not shown). On average, ‘TripleCrown’ had the greatest berry weightand ‘Marion’ the least in both years(Table 1). ‘Black Diamond’ fruit hadthe lowest percent soluble solids inboth years, whereas ‘Triple Crown’fruit had the highest in 2012. ‘Ob-sidian’ had the firmest fruit, and ‘Tri-ple Crown’ and ‘Marion’ fruit werethe least firm in 2011 and 2012,respectively.

Cultivar affected soil nutrientlevels, but the effect varied by year

for many nutrients (Table 3). Soil inthe ‘Triple Crown’ and ‘Black Dia-mond’ plots tended to have the lowestlevel of NO3-N in 2011. In contrast,soil in ‘Black Diamond’ plots had thehighest level of NO3-N in 2012.

The measured primocane tissuenutrient concentrations varied amongcultivars (Table 4). Primocane tissueN, P, K, S, Fe, Cu, and Zn concen-tration were within or above therecommended standards, dependingon cultivar [2.3% to 3.0% N, 0.19% to0.45% P, 1.3% to 2.0% K, 0.1% to0.2% S, 60 to 250 ppm Fe, 6 to 20ppm Cu, and 15 to 50 ppm Zn (Hartet al., 2006)]. Tissue Mn and Mgwere within or below the recommen-ded range depending on cultivar (50to 300 ppm Mn, 0.3% to 0.6% Mg).Primocane Ca and B concentrationwere below the recommended stan-dards in all cultivars (0.6% to 2.0% Ca,30 to 70 ppm B).

Primocane tissue N, P, K, B, Cu,and Zn concentration were highest in‘Obsidian’ and tended to be lowest in

‘Black Diamond’; there were relativelyfew differences between ‘Marion’ and‘Triple Crown’ (Table 4). Tissue Ca,Mg, S, Fe, Mn, and Al were highest in‘Triple Crown’ and tended to be low-est in ‘Black Diamond’.

Harvest date had a significant ef-fect on yield and all fruit quality vari-ables (berry weight, percent solublesolids, and firmness) in all cultivars,which were analyzed separately (P <0.0001 for all cultivars and variables),in 2011 and 2012 (data not shown).There was also a significant effect ofyear on fruit firmness (P = 0.002) andmarketable yield (P = 0.005) for ‘Ob-sidian’, firmness (P = 0.0003) andtotal yield (P = 0.01) for ‘Black Di-amond’, firmness (P = 0.01) and berryweight (P = 0.04) for ‘Marion’, andberry weight (P = 0.002) for ‘TripleCrown’ (data not shown).

There were very different weatherpatterns in 2011 and 2012 (Figs. 1and 2). For example, precipitation inthe month of June 2011 was 0.9inch, whereas in 2012 the same

Fig. 1. Total daily precipitation from 1 June to the end of harvest on 30 Sept. (A) 2011 and (B) 2012 at Oregon StateUniversity’s Hyslop Field Laboratory in Corvallis, OR (U.S. Department of the Interior, 2013); 1 inch = 2.54 cm.

Fig. 2. Maximum (‘‘max’’) and minimum (‘‘min’’) daily air temperature (hourly, 24 h) from 1 June to the end of harvest on 30Sept. (A) 2011 and (B) 2012 at Oregon State University’s Hyslop Field Laboratory in Corvallis, OR (U.S. Department of theInterior, 2013); (�F L 32) O 1.8 = �C.

284 • June 2015 25(3)

RESEARCHREPORTS

month had 2.5 inches of rain; inaddition, there were 1.1 inches inJuly 2011, in contrast to 0.2 inchduring the same month in 2012(data not shown). Although the av-erage air temperature was similar in2011 and 2012 (data not shown), thedaily maximum and minimum tem-peratures were higher in 2011 thanin 2012 (Fig. 2). The harvest seasonin 2012 was �2 weeks earlier than in2011 (Fig. 3).

‘Obsidian’ had the earliest fruit-ing season, followed by ‘Marion’ and‘Black Diamond’ (trailing types) andthe semierect type ‘Triple Crown’.Marketable yield was considerablylower than total yield on certain har-vest dates, particularly for ‘Obsidian’in 2011, ‘Triple Crown’ in 2012, andsome mid and late harvests of ‘BlackDiamond’ in 2012 (Fig. 3).

Berry weight increased throughmost of the fruiting season for ‘Ob-sidian’ in 2011, but remained stableor declined for most of the harvestseason in the other cultivars (Fig. 4).Fruit firmness declined somewhatduring the fruiting season for allcultivars in 2011, while in 2012, fruitfirmness declined considerably duringthe fruiting season, particularly in thetrailing blackberry cultivars (Fig. 5).Percent soluble solids of the trailingblackberry cultivars varied through-out the fruiting season, particularlyin Obsidian and Black Diamond in2011 andMarion in 2012 (Fernandez-Salvador, 2014). In contrast, the per-cent soluble solids of ‘Triple Crown’fruit were relatively consistent throughthe season in both years.

DiscussionThe effect of fertilizer type on

yield and fruit quality was relativelysmall and was inconsistent amongcultivars and years for the variablestested. Soy meal produced the great-est total yield in ‘Triple Crown’ in2011 and in ‘Obsidian’ in both years.In contrast, poultry and fish producedthe greatest total yield in ‘Black Di-amond’ in 2011, and fish producedthe greatest yield in ‘Black Diamond’and ‘Marion’ in 2012. A longer-termstudy would be needed to determinewhether continued use of any of thesefertilizers would have effects over time.

The three organic fertilizerscompared in this study, as is the casewith most organically approved fer-tilizers available (e.g., Fernandez-

Salvador et al., 2015a; Harkins et al.,2014), had different levels of allmacro- and micronutrients. The ad-ditional amount of P, Ca, Mg, Fe,Mn, and Zn present in the poultryfertilizer did not result in measureableincreases in the soil level of thesenutrients in Autumn 2011 and onlyin a higher level of Ca in 2012. Theadditional calcium carbonate in thepoultry fertilizer, originating fromlime added during the productmanufacturing process, may makethis fertilizer of benefit in maintainingthe soil pH in an appropriate range forblackberry (between 5.6 and 6.5) orin mitigating the decline in pH thatoccurs with repeated fertilization inconventional (Chaplin and Dixon,1979; Chaplin and Martin, 1980) ororganic production systems (Fraseret al., 1988; Tester, 1990). In ourstudy, there was no effect of fertilizertype on soil pH in a given year, butmean values declined the least in plotsfertilized with poultry. Longer-termstudies would be needed to deter-mine whether the additional calciumin the poultry fertilizer would besignificant in maintaining soil pH inthe desired range for blackberry (Hartet al., 2006). The use of organicfertilizers in horticultural productionsystems seems to be of benefit inmaintaining a higher soil pH whencompared with synthetic fertilizers ap-plied in conventional systems (Bullucket al., 2002; Clark et al., 1998; Fraseret al., 1988; Liu et al., 2007; Tester,1990).

The additional K and Na appliedwith the fish fertilizer, relative to theother fertilizer types, increased soil Kand Na in both years, in contrast towhat we found in a separate study(Fernandez-Salvador et al., 2015a).Since soil Na also varied by cultivar,Marion and Black Diamond plantsmay have taken up more Na thanObsidian and Triple Crown. The useof liquid fish by-products as fertilizersmay limit the number of applicationsto the soil due to the high Na content(Teuber et al., 2005).

The sensitivity of blackberryplants to Na is not entirely known,but Horneck et al. (2007) suggestedthat blackberry plants are very suscep-tible to excess B and possibly othersalts, with injury appearing at concen-trations above 0.5 ppm in a saturatedpaste extract. In ‘Shawnee’ blackberry,leaf Na was positively correlated with

rate of Na fertilization, with plantsshowing tolerance at low to moderateNa rates but reduced plant growth athigh (6.5 mM) Na levels (Spiers,1993). We did not measure leaf Nain our study, as this is not a commonnutrient analyzed in commercial lab-oratories. Continuous applications offish fertilizer may thus not be a viableoption in an organic blackberry pro-duction system unless the applied Nais leached through irrigation or byrainfall. The use of fish fertilizersshould be evaluated before doingcontinuous applications in drier orsaline and sodic soils as well as inregions with less annual precipitationas suggested in various studies re-garding plant response to salinity(Grattan and Grieve, 1999; Munnsand Termaat, 1986; Parida and Das,2005).

Research on the response of can-eberries to K fertilization is ratherlimited and results have been incon-sistent. When soil and plants are de-ficient in K, growth is often limitedand excessive application of N maylead to K deficiency (Ljones, 1966).In the current study, although the Kapplied in the fish fertilizer increasedsoil K, there was no effect on primo-cane leaf K, Mg, or Ca levels. Incontrast, fertigation with fish in-creased primocane leaf K but had noeffect on soil K in our other study(Fernandez-Salvador et al., 2015a).Shoemaker (1978) also reported thelack of a consistent relationship be-tween leaf tissue K and soil K. Nelsonand Martin (1986) found that leaf Caof ‘Thornless Evergreen’ blackberrydecreased with increased rates of Nand K fertilization. Spiers (1987) alsofound that increased K fertilizationraised tissue K but decreased leaf P,Mg, and Ca concentration and thatafter two growing seasons an in-creased rate of K decreased plantgrowth in ‘Cheyenne’ blackberry.Primocane tissue Ca and Mg maybecome deficient with excessive Kfertilization in ‘Cheyenne’, ‘Boysen’,and ‘Youngberry’ (Ljones, 1966;Spiers, 1987). In contrast, Kowalenko(1981a) found a positive correlationbetween soil and tissue Mg and Kconcentration and K fertilization in‘Willamette’ red raspberry. As we didnot vary the rate of K applied in ourstudy, additional research would beneeded to determine possible correla-tions in an organic production system

• June 2015 25(3) 285

Fig. 3. Seasonal average blackberry total andmarketable yield [11 · 17-ft (3.4 · 5.2m) plot] during the two growing seasons forthe four hand-harvested cultivars in the study: Obsidian (A) 2011 and (B) 2012, Black Diamond (C) 2011 and (D) 2012,Marion (E) 2011, and (F) 2012, Triple Crown (G) 2011 and (H) 2012. Bars indicate SE; 1 kg per 187-ft2 (17.4 m2) plot =57.5610 g�mL2 = 0.1886 oz/ft2.

286 • June 2015 25(3)

RESEARCHREPORTS

Fig. 4. Seasonal average blackberry fruit weight during the two growing seasons for the four hand-harvested cultivars in thestudy: Obsidian (A) 2011 and (B) 2012, BlackDiamond (C) 2011 and (D) 2012,Marion (E) 2011 and (F) 2012, Triple Crown(G) 2011, and (H) 2012. Bars indicate SE; 1 g = 0.0353 oz.

• June 2015 25(3) 287

and the effect of the additional Kapplied in fish fertilizer.

Fertilizer type had no effect onprimocane tissue nutrient levels,

perhaps because soil nutrient levelswere within the recommended rangefor all treatments (Hart et al., 2006),except for soil B, which declined to

deficient levels in the second year.Soils in the Pacific northwesternUnited States are often deficient inB (Hart et al., 2006). Boron

Fig. 5. Seasonal average blackberry fruit firmness during the two growing seasons for the four hand-harvested cultivars in thestudy: Obsidian (A) 2011 and (B) 2012, Black Diamond (C) 2011 and (D) 2012, Marion (E) 2011, and (F) 2012, TripleCrown (G) 2011, and (H) 2012. Bars indicate SE; 1 g-force (gf) = 0.0098 N = 0.0022 lbf.

288 • June 2015 25(3)

RESEARCHREPORTS

deficiency in caneberries may reducepercent budbreak (Chaplin and Mar-tin, 1980) and fruit weight (Kowa-lenko, 1981b). Application of Bfertilizer has been shown to increaseleaf tissue B concentration and im-prove yield in primocane-fruiting ‘Polana’ red raspberry andblack currant [Ribes nigrum (Wojcik,2005a, 2005b)] or may reduce initialyield and have no effect on leaf Bconcentration (Chaplin and Martin,1980). In organic production sys-tems, B could be supplied usingapproved chelated or diluted B infoliar applications or with soil-ap-plied granular products based onsodium tetraborate (OMRI, 2013).

The growth of primocanes inblackberry is mainly dependent onnutrients available in the soil or fromnewly applied fertilizer, in contrast tofloricanes where a large portion of theinitial growth is dependent on re-serves stored in the plant from pre-vious growing seasons (Cortell andStrik, 1997; Malik et al., 1991;Mohadjer et al., 2001; Naragumaet al., 1999). In conventional pro-duction in Oregon, N, P, K, and B arethemain fertilizer nutrients applied toblackberry, and Hart et al. (2006)recommend 31–49 lb/acre of N dur-ing year one or two of establishmentand 49–71 lb/acre of N once theplanting matures; 80 lb/acre of P[as phosphate (P2O5)]; 40–98 lb/acre of K [as potash (K2O)]; and 1–3 lb/acre of B, for conventionalplantings, based on soil and leaf tissuetests. The current primocane leaf nu-trient standards (Hart et al., 2006) arebased on ‘Marion’, but optimumnutrient levels may differ among cul-tivars as found in the present studyand others (Fernandez-Salvadoret al., 2015a; Harkins et al., 2013).In organic production, application ofthe recommended rates of Nmay leadto higher than recommended rates ofother macro- and micronutrients asthe commonly used organic fertilizerscontain a broad range of nutrients.Primocane leaf N concentration wasabove recommended standards in‘Obsidian’ and lowest (althoughwithin recommended standards) in‘Black Diamond’, similar to our find-ings by Fernandez-Salvador et al.(2015b). Harkins et al. (2013) foundthat ‘Marion’ and ‘Black Diamond’differed in leaf N and speculated that‘Black Diamond’ may require more N

fertilizer than ‘Marion’ to maintainadequate plant tissue levels, plantgrowth, and yield.

The level of soil NO3-N in 2011was greatest in ‘Marion’ and least in‘Triple Crown’. In 2012, ‘Marion’,‘Obsidian’, and ‘Triple Crown’ plotsdid not differ in soil NO3-N, whereas‘Black Diamond’ had over 2-foldgreater levels. Cultivars may thus havedifferent N requirements and vary inthe rate of fertilizer used. Nitrogenuptake in the blackberry plant is com-monly related to canopy size (Strik,2008). ‘Triple Crown’, a vigoroussemierect cultivar, may have takenup more N fertilizer as measured bylower soil NO3 in autumn and higherleaf N concentration of primocanes insummer. In contrast, ‘Black Diamond’was observed to have the least vegeta-tive growth in this study, as hasbeen reported elsewhere (Fernandez-Salvador et al., 2015a, 2015b;Harkinset al., 2013), and had the greatest soilNO3-N and lowest primocane leaf Nconcentration. This cultivar may bemore efficient in N use and allocationthan other cultivars (Harkins et al.,2014). The largest proportion of N inthe organic fertilizer sources used inthis study is NH4-N that first needs tobe mineralized to be available to theblackberry plant (Gaskell and Smith,2007; Gutser et al., 2005). Black-berry growers thus need to considertiming of fertilizer application to en-sure NO3-N is available for early pri-mocane growth (Malik et al., 1991;Mohadjer et al., 2001) as well asfertilizer cost. The cost of N, variedfrom $8.16/lb for the liquid fish andmolasses blend, $5.35/lb for the pel-letized soymeal, and $2.54/lb for thepelletized, processed poultry litter. Amore comprehensive cost analysis in-cluding delivery method and/or ap-plication cost should be conducted todetermine actual costs of using differ-ent types of organic fertilizers. Liquidsources of fertilizer can be appliedthrough the drip irrigation system(fertigated) in organic blackberry pro-duction (Fernandez-Salvador et al.,2015a, 2015b; Harkins et al., 2013),reducing cost of application comparedwith the method used in this study.

Total yield increased consider-ably from 2011 to 2012, as the plant-ing matured in all cultivars exceptMarion. Fruit quality and marketableyield improved from 2011 to 2012,possibly due to the implementation of

timely preventative fungicide applica-tions for control of botrytis gray moldand other fungi, to which the earlyripening cultivars are more sensitive ifweather conditions are conducive forthe spread of the disease. The seasonfor these cultivars varies with Obsid-ian ripening earliest, followed byBlack Diamond and Marion with Tri-ple Crown ripening the latest. ‘Ob-sidian’ is typically exposed to themostrainy wet, rot-inducing weather and‘Triple Crown’ the least.

Total and marketable yield werecomparable to the yield of hand-harvested fruit in conventional sys-tems, in particular for the fresh marketcultivars Obsidian and Triple Crown(B.C. Strik, personal observation).Siriwoharn et al. (2004) showed thatpercent soluble solids varied with cul-tivar (Marion and Thornless Ever-green) and with stage of maturity(underripe, ripe, overripe). The pres-ent study confirms such findings, as allcultivars differed in percent solublesolids, particularly in 2012, perhapsdue to weather conditions. Althoughfruit firmness has been shown to de-cline with fruit maturity (Stiles andTilson, 1998), we also found thatfirmness declined through the harvestseason for many cultivars as tempera-tures increased.

‘Obsidian’ is an early ripening,high-yielding, fresh market cultivarproducing uniformly shaped fruit(Finn et al., 2005b). In our study,‘Obsidian’ was the earliest to harvest,being 6 to 10 d earlier than ‘BlackDiamond’ and ‘Marion’. ‘Obsidian’had a similar yield, but a greater av-erage fruit weight greater than whathas been reported in conventionalproduction (Finn et al., 2005b).However, marketable yield in ourstudy was lower in 2011 than in2012, likely because of a higher in-cidence of fruit rot. Weather eventsmay have influencedmarketable yield,as precipitation on 15 July (over 0.4inch and over 0.1 inch in 2011 and2012, respectively) preceded ‘Obsid-ian’ harvest in both years increasing theincidence of fruit rot. In 2012, thegrower responded by applying preven-tative, OMRI-listed fungicides in an-ticipation of precipitation events likelyreducing the quantity of cull fruit.

‘Black Diamond’ producedlarger fruit in this study as well as inFernandez-Salvador et al. (2015a)than had been previously reported

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in conventional production (Finnet al., 2005a), or organic, machine-harvested production (Harkins et al.,2013). Total yield was lower in‘Black Diamond’ when comparedwith a 3-year-old conventional planting(Finn et al., 2005a) and a greater yieldthan reported in an organic, machine-harvested trial (Harkins et al., 2013).‘Black Diamond’ fruit had lower per-cent soluble solids than the other cul-tivars, agreeing with other studies(Fernandez-Salvador et al., 2015a,2015b; Harkins et al., 2013), but con-trasting those reported by Siriwoharnet al. (2004). ‘Black Diamond’ fruitwere similar in firmness to those of‘Obsidian’, agreeing with previous re-ports (Fernandez-Salvador et al.,2015b; Finn et al., 2005a; 2005b).

This study confirmed that ‘Mar-ion’ fruit are too soft for the freshmarket. Fruit weight was similar, butyield was lower than what has beenreported in other hand-picked studies(Finn et al., 1997). Fruit percentsoluble solids was lower in our study(12.4% on average) than what hasbeen reported in conventional ma-chine-harvested fruit for individuallyquick-frozen (IQF) in Oregon [13.6%(Finn et al., 1997)], likely becausehand-harvested fruit are picked at allstages of ripeness, thus reducing aver-age percent soluble solids, whereasharvest by machine selects mostly ripefruit at a more uniform stage of matu-rity. In an organic machine-harvestedsystem, ‘Marion’ fruit had higherpercent soluble solids (Fernandez-Salvador et al., 2015a; Harkins et al.,2013) than in the current study.

‘Triple Crown’ produced thelargest fruit, heavier than what hasbeen previously reported for conven-tional production (Galletta et al.,1998), and had the greatest yield.Fruit soluble solids content was similarto what has been previously reported(Galletta et al., 1998), but fruit firm-ness ranked near the lowest of thecultivars studied, an undesirable traitfor a fresh market cultivar. As ‘TripleCrown’ ripens in the latest part of thesummer in Oregon, when the weatheris warm and dry, this cultivar can pro-duce fruit that vary in firmness. Fruitwere prone to sunburn,which reducedthe proportion of marketable fruit in2012. The high maximum tempera-tures (above 90 and 85 �F in 2011 and2012, respectively) are commonly re-lated to increased damage from

ultraviolet light (sunburn) and pre-ceded harvest dates of ‘Triple Crown’in both years. The sensitivity of ‘TripleCrown’ to sunburn and its shortershelf life due to fruit softness has beenreported as undesirable traits of thiscultivar by fresh market blackberrygrowers (J.A. Fernandez-Salvadorand B.C. Strik, personal observation).

ConclusionsThe three organic fertilizers

compared in this study were suitableto maintain adequate nutrition inorganic blackberry production, butsupplemental applications of B maybe needed in deficient soils. Poultrylitter may offer advantages in black-berry production to help mitigate thedecline in soil pH that occurs whenfertilizing. The fish fertilizer contrib-uted relatively large amounts of so-dium to the soil with no adverseeffects observed. Of the three fertil-izers, the cost per pound of N washigher for the liquid fish and molassesblend than for the pelletized soymeal,and the pelletized, processed poultrylitter, but a comprehensive cost ben-efit analysis of organic fertilizer op-tions considering plant availabilityand mineralization rate of N isneeded. All cultivars performed welland would be considered suitable forcommercial organic production. ‘Tri-ple Crown’ produced the highestyield and largest fruit weight, butwas considered soft for a fresh market,shipping cultivar. In contrast, ‘Obsid-ian’ fruit was the firmest, but weremore sensitive to gray mold indicat-ing the importance of a good or-ganic disease management programin the early season. ‘Marion’ and‘Black Diamond’ had traits thatmake these cultivars more suitable,as expected, for processing. Yieldand fruit quality variables were influ-enced by harvest date and seasonalchanges where weather conditionsfrom year to year are importantconsiderations for successful com-mercial organic production.

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