micro irrigation - technology and applications

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Micro irrigation is a water saving irrigation technology. It corresponds to harsh environmental conditions like water scarcity, hot spells, high water and soil salinity etc. it appears in wide range of water application rate, water spread pattern and different levels of sophistication and cost.




FOREWORDSince my retirement from the Irrigation and Soil Field Service, on October 2001, after 24 years of service as field adviser and 12 years as its manager, I had been asked to share my experience and know-how with local and foreign farmers. That had been implemented in courses, surveys and counseling abroad, as well as in written publications printed by CINADCO and ICID, and in personal exchange by mail and email. Irrigation technology is so dynamic that updated publication becomes partially obsolete in two or three years. The opportunity of uploading professional material to the web by means of the Scribd system enables me to distribute in real time recently updated material. The author September 24 2009

AUTHOR'S NOTESince the upload of the first version of this document, on September 24th, I received some dozens of e-mails from readers with comments and suggestions for improvements in the document. I found some of the comments and suggestions worthwhile to be embedded in the document. Additionally, I made adjustments on my own initiative and replaced some outdated figures in this second version. I would like to thank all the responders for their valuable contribution. November 28 2009



CONTENTFOREWORD CONTENT LIST OF TABLES LIST OF FIGURES INTRODUCTION MICRO IRRIGATION Introduction ... Micro-emitter Classification Terminology .. Water Distribution Uniformity . DRIPPERS: STRUCTURE AND FUNCTION Introduction ... Types of Drip Systems Lateral type ... Water Passageway Structure and Characteristics . Position on Lateral ........................ Dedicated Drippers . Integral Filtration in Drippers . Auto Flushing Mechanisms MICRO-JETS AND MICRO-SPRINKLERS Introduction .. Static Micro-jets ......................... Vibrating Micro-jets . Micro-sprinklers Bubblers ......................... Water Distribution Patterns Pressure Compensation . Emitter Mounting . THE MICRO-IRRIGATION SYSTEM COMPONENTS The Water Source ... The Delivery System ... Laterals .. Control and Monitoring Devices Sub Surface Drip Irrigation (SDI) .. Low-Cost Drip Irrigation Systems ....................... PIPES AND ACCESSORIES Polyethylene Pipes .. PVC Pipes Lay flat hoses Fiberglass Pipes .. External and Internal Pipe Diameters .. Accessories .. WATER TREATMENT AND FILTRATION Physical Quality Parameters . Chemical Quality Parameters Emitter Clogging Factors Water Hardness ... Iron and Manganese in Water .. II

Page I II V VI 1 2 2 2 3 4 7 7 7 8 8 10 11 14 14 15 15 16 16 16 17 18 19 20 21 21 21 22 22 24 25 28 28 29 30 30 31 31 37 37 37 37 38 38

1 2 2.1 2.2 2.3 2.4 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 5 5.1 5.2 5.3 5.4 5.5 5.6 6 6.1 6.2 6.3 6.4 6.5 6.6 7 7.1 7.2 7.3 7.4 7.5

7.6 Biochemical Oxygen Demand (BOD) .. 7.7 Filtration 7.8 Supplementary Water Treatments 8 FERTIGATION 8.1 Fertilizer Tank .. 8.2 Venturi Injector . 8.3 Injection Pumps ... 8.4 Injection Site . 8.5 Control and Automation .. 8.6 Avoiding Corrosion Damage ....................... 8.7 Back-Flow Prevention . 9 MONITORING AND CONTROL 9.1 Monitoring . 9.2 Irrigation Control .. 10 FLOW RATE PRESSURE RELATIONSHIP 10.1 Water Pressure 10.2 Head Losses 10.3 Operating Pressure 10.4 Hydraulic Characteristics of Emitters ... 10.5 Calculation of the Head Losses 10.6 Technical Data . 11 WATER DISTRIBUTION 11.1 Soil Wetting Patterns . 11.2 Salt Distribution ... 11.3 Soil Properties that Affect Water Distribution Pattern 11.4 Wetting Width and Depth ... 11.5 Nutrient Distribution . 11.6 Root System Development Under Drip Irrigation ..................... 12 PLANNING OF MICRO IRRIGATION SYSTEMS 12.1 Introduction ... 12.2 Planning 12.3 Data Manipulation.......................... 12.4 Existing Equipment . 12.5 Planning of Drip Irrigation for Different Crops ...................... 13 DESIGN OF MICRO IRRIGATION SYSTEMS 13.1 Basic Guidelines ....................... 13.2 The Design Procedure 13.3 Design of Drip Irrigation System for Row Crops . 13.4 Sub-Surface Drip Irrigation (SDI) ....................... 13.5 Design of Drip Irrigation in Protected Crops 13.6 Design of Irrigation Systems in Greenhouses 13.7 Drip Irrigation Design for Orchards .. 13.8 Design of Micro-jet and Micro-sprinkler Systems for Orchards 14 MAINTENANCE OF MICRO IRRIGATION SYSTEMS 14.1 General . 14.2 Critical Issues in Installation .. 14.3 Routine Inspection ........................ 14.4 Routine Maintenance ....................... 14.5 Chemical Water Treatments .

39 39 47 49 49 49 50 51 51 52 52 53 53 55 57 57 58 61 62 64 64 67 67 69 69 70 70 71 72 72 72 74 78 79 85 85 85 88 98 99 100 100 110 117 117 117 118 119 122


15 16 17


123 128 133


No. 6.1 6.2 6.3 6.4 6.5 6.6 7.1 7.2 7.3 7.4 7.5 10.1 10.2 10.3 10.4 10.5 10.6 10.7 13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8 13.9 13.10 13.2 13.11 13.12 13.13 13.14 13.15 13.16 13.17 13.18 13.19 13.20 13.21 13.22 13.23

LIST OF TABLESPE (polyethylene) pipes for agriculture. LDPE pipe internal diameter and wall thickness. HDPE pipe inner diameter and wall thickness. PVC pipes for agriculture Rigid PVC pipes internal diameter and wall thickness... Spring actuated pressure regulators. Relative clogging potential of drip irrigation systems by water contaminants. Characteristics of water passages in drippers (example).. Screen Perforation Examples Sand particle size and mesh equivalent... Nominal filter capacity examples ... Pressure and water potential units ... Friction Coefficients Multiple outlets factor F .. Effect of dripper exponent on pressure flow rate relationships . Example of integral drip lateral technical data Max. Allowed lateral length for non-compensated line drippers (example) . Allowed lateral length for pressure compensated drippers (example) Compensating dripper (compensating pressure threshold 4 m) data . Max. Lateral length m, Model 16012, ID = 13.70 mm, Inlet pressure 3.0 bars .. Max. Lateral length m, Model 16009, ID = 14.20 mm, Inlet pressure 3.0 bars .. Non compensating thick wall dripper pressure flow rate relationship . Max. Lateral length in non compensating thick wall dripper . Non compensating thin wall dripper . . Max. Lateral length in non compensating thin wall dripper The compatible drippers Design Form: COMPENSATING RAM DRIPPER 16012, 1.6 L/H, PRESSURE IN INLET 30 m Thin-wall tape data .. (Duplicate) Max. Lateral length m 16012 compensating dripper laterals Basic data . HEAD LOSSES CALCULATION FORM . Head Losses In The Control Head, flow rate 56 m3/h ... Head Losses In The Hydraulic Valves On The Sub-Mains flow rate 14 m3/h ... Total requested dynamic head . Second alternative compensating dripper laterals Basic data .. Head-loss calculation .. Total requested dynamic head . The chosen emitter - Non regulated Jet sprayer performance data Allowed length of laterals, Emitter type: Jet+ (Red) lph . Basic data . Head-loss calculation .. Total requested dynamic head ..

Page 28 29 29 30 30 34 38 39 40 42 44 57 52 62 63 65 65 66 89 89 89 90 90 91 91 92 94 97 103 104 106 106 107 107 108 109 109 111 112 113 115 115


No. 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.1 5.2 5.3 5.4 5.5 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 7.1

LIST OF FIGURESPoint-source (left) and line-source (right) wetting patterns by drippers . In-line barbed semi-turbulent dripper and in-line integral turbulent dripper .. Evolution of the passageway style .. Turbulent flow .. Orifice dripper . Vortex dripper .. Labyrinth button dripper . Tape dripper lateral: empty and filled with water ... On-line drippers .. Button drippers connector design Adjustable dripper and flag dripper Flexible diaphragm under pressure . Button and inline PC drippers ... Cylindrical PC dripper: water passageway length changed under high pressure Flap equipped dripper Woodpecker drippers . Arrow dripper for greenhouses, nurseries and pot plants Six outlets dripper .. Ultra low flow micro-drippers Integral dripper filters . Auto flushing, pressure compensating dripper .. Micro-emitters . Modular Micro-emitters . Static micro-jets .. Vibrating micro-jet, micro-sprinklers and vortex micro-jet Modular micro-sprinkler . Bridge micro-sprinkler and bubbler .. Water distribution by micro-sprinkler at different flow rates . Ray-jet (fan-jet) distribution patterns ... Micro-emitters mounting alternatives .. Typical layout of drip irrigation system Control head Bucket and drum kits Family Drip System (FDS) Treadle pump at work and close-up Plastic and metal connectors Start connectors, plugs and lateral ends Lock fastened connectors . Connectors and splitters Valves ... Hydraulic valve operating principle .. Pressure regulators Control valves . Air Relief Valves . Atmospheric vacuum breakers . Lateral-end flushing action Lateral-end flusher components .. Screen filter . VI

PAGE 8 9 9 9 9 9 9 10 10 10 11 11 11 11 12 12 13 13 14 14 14 15 15 16 17 17 18 19 19 20 22 24 25 26 27 31 32 32 32 32 33 33 34 35 36 36 36 40

7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 7.10 7.11 1.12 8.1 8.2 8.3 8.4 8.5 8.6 8.7 9.1 9.2 9.3 9.4 9.5 9.6 10.1 10.2 10.3 10.4 10.5 11.1 11.2 11.3 11.4 11.5 11.6 11.7 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 12.9 12.10 13.1 13.2 13.3

Head losses in clean screen filters .. Disc filter .. Media filters . Sand separator working pattern ... Hydro-cyclone sand separator head losses and optimal flow rates Automatic flushing of disk filter . High capacity media filter array Back-flushing of media filters High capcity automatic filter .. Compact automatic filter Treflan impregnated disc filter and its discs stack . Fertilizer tank ... Venturi injector Piston and diaphragm hydraulic pumps . No-drain hydraulic pump ... Mixer array ... Electric pump .. Tandem backflow preventer . Tensiometers .. Watermark granular sensor .. Time domain transmissometry sensor . The pressure bomb .. Fertilizer and water controller ... Integrated monitoring and control On-line Dripper Connection .. Head losses in hydraulic valves ... Relationship between the dripper exponent and lateral length ... Non-pressure compensating flow-pressure relationships Pressure Compensating dripper flow-pressure relationship Water distribution in the soil: in on-surface drip irrigation. And in SDI .. Water distribution from a single dripper in loamy and sandy soil. 4 l/h and 16 l/h flow rates, 4, 8, 16 l dose .. Salt distribution in the wetted volume . Leaching of salt into the active root-zone by rain .. Diverse root systems . Typical root systems of field crops .. Root system in sprinkler irrigation vs. root system in drip irrigation ... Wetting patterns by drippers in different soil types ... Ellipsoid Drip irrigation layouts in orchards Dripper layouts in wide-spaced orchards Mechanized deployment of drip laterals . Cotton root development ... Potatoes - Laterals on top of hillocks .. Wide-scale drip irrigation in greenhouses .. Drip irrigation of potted plants in greenhouse Roadside drip irrigation .. Different design layouts . Manifolds save accessories cost . Maize retrievable drip irrigation system layout ..

40 41 41 42 43 45 46 46 46 46 47 49 49 50 50 51 51 52 53 53 53 54 55 56 59 60 63 64 64 67 68 69 69 71 71 72 74 76 78 78 80 80 81 83 84 84 86 87 93


13.4 13.5 13.6 13.7 13.8 13.9 13.10 13.11 13.12 14.1 14.2 14.3 15.1 15.2 15.3 15.4 15.5

SDI layout thin-wall non-compensating laterals in strawberries excessive head losses Apple orchard 9.6 Ha .. Non-compensating on-line drippers flow rate -pressure relationship . Two of the feasible layouts .. Non- compensating drip system .. Compensating drip system Citrus grove - 11.5 ha. ... Micro-jet irrigation system in citrus grove ... Punch and holder Automatic lateral end flushing valve Vertical stake .. Nomogram for calculation of head losses in water flowing in pipes ... Nomogram for calculation of head losses in LDPE pipes. Class designation relates to the working pressure (PN) in bar Nomogram for calculation of head losses in HDPE pipes. The class designation relates to the working pressure (PN) in bar Nomogram for calculation of head losses in PVC pipes. The class designation relates to the working pressure (PN) in bar Nomogram for calculation of local head losses in valves and other accessories and fittings

98 99 101 103 104 105 108 111 114 117 119 120 123 124 125 126 127


1. INTRODUCTIONWater scarcity, soaring energy costs, deterioration of agricultural land and desertification, threaten agricultural development and food production for the fast growing world population. Irrigated agriculture increases yield per land unit twice up to ten-fold, compared to non-irrigated farming. The principle irrigation technologies are surface irrigation, mechanized irrigation, sprinkler irrigation and micro irrigation. Surface irrigation is regarded as the most wasteful technology. Irrigation efficiency is mostly below 40%. In sprinkler and mechanized irrigation, the efficiency ranges from 60% to 85%. In micro irrigation, the efficiency can attain 90% - 95%. Micro irrigation is well-suited to harsh environmental conditions. Partial wetting of the soil volume, superior emission uniformity and a high level of water application control, facilitate efficient utilization of restricted water resources. The application of the water in partial, limited soil volume improves the leaching of salts out of the active root-zone. This raises the upper threshold of permitted salt content in irrigation water than with full surface wetting technologies. The frequent applications of water that are mandatory in micro irrigation dilute the soil solution and keep salt concentration low. Drip irrigation, in particular, minimizes evaporation losses from the air and soil surface compared with sprinkler, border and furrow irrigation. Salinization of irrigated lands is one of the most widespread causes of desertification (conversion of cultivated land to desert). More than one million hectares of arable land are lost every year due to salinization. Micro irrigation, particularly drip irrigation, facilitates the suspension of this process by leaching the accumulating salts out of the active root-zone. The amount of water needed for adequate salt leaching is significantly smaller than the leaching requirement in sprinkler, border and furrow irrigation. Wide-scale use of drip irrigation commenced in the Middle East, in arid regions in Israel and disseminated extensively in arid and semi-arid areas all over the world. The concept of Regulated Deficit Irrigation (RDI) - partial replenishment of the water consumed by the crop is gaining momentum in arid and semi-arid regions. Under this irrigation regime, the varying stress sensitivity in different phenological phases is exploited to reduce water dosage. In the tolerant phases, the soil water deficit is only partially replenished, maintaining the crop in mild stress that has no serious impact on yield and the produce quality. In some crops, salinity can be exploited to improve produce quality. High salt content in irrigation water improves the produce quality in tomatoes and melons, at the expense of yield. An economical balance point exists in which the premium for quality compensates for loss in yield.


2. MICRO IRRIGATION 2.1. IntroductionThe term micro irrigation refers to irrigation technologies employing water emitters with tiny apertures that deliver water at a low flow rate. There is no definite distinction between low volume sprinklers for irrigation and micro-sprinklers used in micro irrigation, but emitters with flow rates lower than 200 l/h can be regarded as micro emitters. Micro irrigation is one of the pressurized irrigation technologies alongside sprinkler irrigation and mechanized irrigation technologies. Four principal characteristics distinguish micro irrigation from the other pressurized irrigation technologies: a. Low flow rate b. Localized, partial wetting of the soil surface and soil volume while in sprinkler irrigation in field crops and vegetables the soil surface is wetted entirely. c. Frequent water applications are needed due to the limited wetted volume. d. Low operating pressure, compared with sprinkler irrigation.

2.2 Micro-emitters ClassificationMicro-emitters are classified in two principal groups in respect to water emitting patterns. The functional objectives of the emitters are distinctive in both groups. In the first group, water is applied directly to the soil in discrete drops (by drippers) or as a continuous stream (by bubblers). The objective of the water passageways is to maximize pressure dissipation, to approach atmospheric pressure in the emitter outlet. In the second group, water is conveyed through the air and applied to the soil as spray, mist or multiple discrete jets. Pressure dissipation is kept to a minimum in order to enable the water to be adequately spattered on the desired surface area. Each group is further subdivided in regard to the working patterns:

2.2.1. Emitters for direct application to the soil: Drippers Bubblers 2.2.2. Emitters for water application through the air: Static emitters Sprayers Ray microjets (fan-jets) Misters and foggers Vibrating emitters Rotating emitters

2 Micro sprinklers Rotators SpinnersMicro irrigation holds four obvious advantages over most other irrigation technologies: a. b. c. d. High efficiency in water application. Improved plant nutrition management. Better salinity handling. Low energy requirement compared with sprinkler and mechanized irrigation.

The basic planning and design procedures are similar in the two micro irrigation technologies. Since drip irrigation is the most widespread technology, it receives more coverage than spray technology in this publication.

2.3. TerminologyCertain terms relating to irrigation have different interpretations in micro irrigation than in conventional sprinkler irrigation.

2.3.1. Application RateIn full surface area wetting technologies such as sprinkler or border irrigation, the application rate is designated as the volume of water applied over area unit during a time unit. The application rate is expressed in units of l/m2/hour, m3/ha/hour or mm/hour. The last unit indicates the depth of the applied water volume equally spread on the irrigated area. E.g.: 1 mm water depth over 1 m2 area (1,000,000 mm2) is: 1 mm 1,000,000 mm2 = 1,000,000 mm3 (micro liters). 1,000,000 micro liters = 1000 milliliters = 1 liter/1 m2. Since 1 ha consists of 10,000 m2, 1mm water depth = 10,000 l/ha = 10 m3/ha. In localized micro irrigation, the water does not spread evenly on the soil surface. The term Irrigation Rate (IR) designates a virtual value. The applied water quantity per hour over the irrigated area is addressed as if coverage is uniform. The virtual irrigation rate per single emitter will be its flow rate over spacing between emitters.

Example:Emitter flow rate: 2 l/h Spacing 3 0.5 m Irrigation Rate = 2 / (3 0.5) = 1.333 l/m/h = 13.33 m3/ha/h

2.3.2. Water DistributionThe water that spread unevenly on the soil surface and in the soil volume makes it impractical to consider Distribution Uniformity the same as in sprinkler and border irrigation. The wetted volume by a single emitter has variable moisture levels as a function of distance from emitter, soil properties and water dose. Hence the uniformity of water distribution in micro irrigation is expressed differently than in sprinkler irrigation. The common term is Emission Uniformity (EU) that indicates the variance between emitters in a representative sample. The calculation for EU is the same as the calculation for DU but it relates to variance between emitters and not to application to area unit. 3

2.3.3. Distribution of ChemicalsThe distribution of dissolved chemicals (salts, nutrition elements) in micro irrigation has also different pattern than in other irrigation methods. This pattern is beneficial for nutrition and salt management but obliges strict precautions to be taken in acute climatic events like heat spells and early rains after a dry period.

2.4. Water Distribution Uniformity2.4.1. Irrigation EfficiencyIrrigation Efficiency (IE) is an important parameter for the evaluation of irrigation excellence. Water beneficially used IE =--------------------------------------------------

(Eq. 2.1)

Total applied water

Water beneficially used is the sum of the water amounts applied for the replenishment of water used for evapo-transpiration from the plant and the soil surface, for fertilizer and pesticide application, for salt leaching, for frost protection and for crop cooling. Micro irrigation facilitates the application of even volume of water to every plant in the irrigated plot. This requires suitable spacing between laterals and emitters as well as an appropriate pressure regime. Application Uniformity can be expressed by different indices. A uniformity of 100% means that each point within the plot area gets exactly the same amount of irrigation water. When uniformity is low, certain sections of the plot receive less water than others. In order for those sections to receive sufficient amount of water, extra water amount has to be applied to the plot as a whole. As the application uniformity is lower, the required amount of extra water will be greater. Application uniformity is particularly important with drip irrigation systems, due to the cumulative nature of non-uniformity embodied in factors that determine the dripper's flow rate.

2.4.2. Distribution UniformityA common index of application uniformity is DU (Distribution Uniformity). For calculating this value, the flow rate of a representative sample (40 - 100 emitters randomly selected in different sections of the irrigated plot) is measured. Q25% (Eq. 2.2) DU = 100 -----------------Qn Where: Q25% is the average flow rate of 25% of the emitters with the lowest flow rate, and Qn is the average flow rate of all the sampled emitters. DU significance: >87% - excellent distribution uniformity 75% - 87% - good uniformity 62% - 75% - acceptable 100 outlets. Hf = The calculated friction head loss according to the pipe inner diameter, its smoothness, its length and number of outlets. Hz = The effect of topography expressed in m height. Minus sign designates descending slope. Table 13.13. HEAD LOSSES IN THE CONTROL HEAD, flow rate 56 m3/h Component Riser Hydrometer Filter Total Diameter 4- 1 m high 4 3 - pair Kv = 150 Back-flush threshold 5 m Characteristics Head-loss - m 0.03 1.4 5 6.4


Table 13.14. HEAD LOSSES IN THE HYDRAULIC VALVES ON THE SUBMAINS flow rate 14 m3/h Pressure reducing valve 2 Kv = 50 0.8 m

Table 13.15. Total requested dynamic head Operation pressure Topographic difference (max) Friction head losses in lateral Friction head losses in manifold Friction head losses in mainline Control head Pressure reducing valves Total 10 m 2 m* 0.5 m 1.5 m 7.9 m 6.4 m 0.8 m 29.1 m

Comments a. In a cycle of 2 days, blocks a, d, e and h will be irrigated on day 1; blocks b, c, f and g will be irrigated on day 2. In order to equalize the pressure in the simultaneously irrigating blocks, the hydraulic valves on the submains will be of the pressure reducing valves type. b. Laterals of class 4 (not of class 2.5) had been chosen in order to guarantee wall thick enough to fasten the dripper barb for the long run. c. In order to better handle the topographic slope, the submains are not laid in the middle of the blocks but closer to the higher ground. d. Since the actual operating pressure in the drippers will be in the range of 10 12 m, the actual flow rate of the blocks will be 5% 10% higher than the designed flow rate that does not affect significantly the pressure regime. Actually, in designing it is taken into account that the average flow is a little bit higher than the nominal.


Second alternative compensating dripper lateralsTable 13.16. BASIC DATA Parameter Integral compensating dripper Lateral Drippers distance on lateral Drippers per lateral Number of laterals per block No. of blocks in the plot Irrigation cycle Flow rate per a single shift Unit piece m m piece piece Sub plot day .m3/h Amount 1 40 0.6 40/0.6 = 67 60 8 2 112.8/2 = 56.4 m3/h 3.5 l/h 67 = 235 l/h 60 0.235= 14.1 m3/h 112.8 m3/h Nominal flow rate 3.5 l/hour

Fig. 13.10. Compensating drip system


Table 13.17. Head-loss calculation Segment Flow Length N.D rate -m .mm/class 3/h m FG Lateral 0.23 40 150 240 40 40 150 120 40 150 40 40 150 120 16/4 50/4 PVC 110/6 PVC 110/6 16/4 50/4 PVC 110/6 16/4 50/4 PVC 110/6 16/4 50/4 PVC 110/6

H f Outlets Ffactor -% 4.2 8 0.9 2.6 4.2 8 2.6 4.2 8 2.6 4.2 8 2.6 67 30 0 0 67 30 0 67 30 0 67 30 0 0.36 1 0.36 1 0.35 1 0.36 1 1



Hz - Total Cumulative m H- H - m m 0.5 0.5 -1.5 0 0.5 1 -0.5 0.5 2 0 0.5 2 -0.5 1.5 4.7 0.7 1.1 1.5 5.2 2.6 1.5 6.2 1 1.5 6.2 2.6 1.5 6.2 6.9 8.0 1.5 6.7 9.3 1.5 7.7 8.7 1.5 7.7 11.8

1.0 4.2 2.2 1 1.0 4.2 3.1 1.0 4.2 1 1.0 4.2 3.1

EF 14 Manifold BE Mainline AB Mainline KL Lateral 28 56 0.23

IK 14 Manifold AH Mainline CD Lateral 56 0.23

BC 14 Manifold AB Mainline JM Lateral 56 0.23

HJ 14 Manifold AH Mainline 56

Table 13.18. Total requested dynamic head Pressure requested in lateral distal end Head loss in lateral Maximum head loss in manifold Maximum head loss in mainline Topographic difference Control head losses Total

10 m 1.0 m 4.2 m 3.1 m 2m 8m 28.15 m


Comments a. Using compensating drippers renders more flexibility in design and allows for higher head losses in the distributing system. b. Additional advantage of using compensating drippers is the capability to run longer laterals and save manifolds. This advantage is not presented in the example since in case of use of longer laterals, the manifolds have to be replaced by pipes of larger diameter. c. The major advantage of the compensating dripper is the high level of uniformity in harsh topographic conditions. d. As mentioned before, in coarse textured soils and in shallow lands, two laterals per row are the favored layout. The distance between the two laterals is 80 150 cm, depends on the space between the rows and the soil characteristics.

13.8. Design of Micro-jet and Micro-sprinkler Systems in OrchardsMicro-jets and micro-sprinklers have flow rates in the range of 20 200 l/h. The common layout in orchards is of one lateral per row. In densely planted rows 2-3 m distance between trees in the row, one emitter can suffice per two trees. Over 3 m space in the row, one emitter per tree is the prevalent layout. In some more spacious plantations with spacing greater than 6 6 m, two emitters per tree are frequently installed. The placement of the emitter in the row depends on the shape of the tree canopy. In those crops that the canopy leaves considerable height above soil surface free for water distribution, the emitter is placed in the middle between two trees. In trees that their canopies bend toward the soil surface, converge with each other in the middle between the two trees, the emitter is placed 0.5 1 m from the trunk. Like drippers, there are pressure compensating and non-pressure compensating emitters. The choice between micro-sprinklers, micro-jets and ray-jets takes place in respect to spacing, soil type and crop response. In spacious spacing, microsprinklers that wet greater area are favored, in densely planted orchards, micro-jets are more suitable and in heavy and compact soils, prone to run-off, as well as in windy conditions, ray-jets are the best performers.

Example Crop Data Crop: Citrus Variety: Washington Navel Area: 11.5 Ha. Partition: 4 blocks, 80 X 360 m, each Topography: 3.5 m slope from NW to SE Spacing: 6 X 4 m


Irrigation season: April - October Harvest: October-December Active root system depth: 100 cmMaximum allowed water depletion: 60%

Peak-season average evaporation: 7 mm/day Soil data Texture: Loamy clay Depth: 1.20 1.50 m Bulk Density: 1.4 Field Capacity: 32% V/V


Peak-season crop coefficient: 0.7

Permanent Wilting Point: 15% V/V Available Water: 17% V/V Percentage of wetted area: 60% Climate Data Peak season average daily class A pan evaporation: 8 mm Water Supply Data Maximum supply hours: 20 hours a day Maximum available discharge: 150 m3/h EC water: 1.2 dS/m Chloride content: 150 mg/l Calculation of daily Peak Season Water Demand Daily average evaporation Crop coefficient = 8 mm 0.7 = 5.6 mm/day Gross daily demand, assuming application efficiency of 80%: 5.6/80% = 7 mm/d hourly

Fig. 13.11. Citrus grove - 11.5 ha. Table. 13.19. the chosen emitter Non regulated (non compensating) Jet sprayer performance data Nozzle color code Blue Pressure bars 1.5 2.0 2.5 3.0 Green 1.5 2.0 2.5 3.0 Red 1.5 2.0 2.5 3.0 Flow rate Wetting l/h diameter m 55 64 70 77 64 75 83 91 90 102 115 126 5.6 5.8 6.0 6.2 6.6 7.0 7.2 7.8 8.2 8.6 9.2 9.8


Soil water reservoir volume per ha: Inter row spacing root system depth wetted area percentage = 10,000 m 60% 1.00 m = 6000 m3 Easily available water soil capacity = resrvoir volume available water (%) Allowed deplition (%) = 6000 m3 17% 60% = 612 m3/ha. = 61.2 mm Max interval between irrigations = easily available water soil capacity / daily demand = 61.2 mm / 7 mm/day = 8.75 days For sake of convenience, the interval will be 7 days and not the allowable maximum. Irrigation dose: 7 mm/day 7 days = 49 mm. Minimum acceptable application rate: 49 mm/20hours of water supply = 2.45 mm/hour. Minimum emitter flow rate in 46 m spacing: 2.45 mm/(46)m = 102 l/h Choice of emitter The chosen emitter is non-regulated (non-compensating) jet+ with nominal flow rate of 102 l/h in 20 m head.Table 13.20. Allowed length of laterals


Table 13.21. BASIC DATA Parameter Micro-jet Lateral Emitters distance on lateral Emitters per lateral Number of laterals per block No. of blocks in the plot Irrigation cycle Days of irrigation in a cycle Flow rate per a single day Unit piece m m piece piece unit day day .m3/h Amount 1 40 4 40/4 = 10 60 8 7 4 489.6 / 4 = 122.4 m3/h 102 l/h 10 = 1.020 l/h 61.2 m3 489.6 m3/h Nominal flow rate 102 l/hour

The chosen lateral is the 20/4 mm (20/17 mm OD/ID). It allows for 11 emitters on the lateral, in the range of pressure difference of 7.5% in 1% ascending slope.


Fig. 13.12. Micro-jet irrigation system in citrus grove


Table 13.22. Head-loss calculation Segment Flow rate m3/h EF DE DG BD KL IK MN IM BI RS OR PQ OP BO UV TU WY TW BT 1.02 24 36 60 1.02 24 1.02 36 60 1.02 24 1.02 36 60 1.02 24 1.02 36 60 Length -m N.D./PN mm/class 20/4 75/4 75/4 PVC 110/6 20/4 75/4 20/4 75/4 PVC 110/6 20/4 75/4 20/4 75/4 PVC 110/6 20/4 75/4 20/4 75/4 PVC 110/6 H f Outlets Ffactor -% Hf m-

Hz - Total Cumulative m H- H - m m 0.5 1.0 -1.0 1.0 0.5 0 0.5 -0.5 -2.0 0.5 1.0 0.5 -1.0 0.5 0.5 1.0 0.5 -1.0 -05 2.3 2.0 2.0 4.4 2.3 1.0 2.3 2.5 9.6 2.3 2.0 2.3 2.0 7.3 2.3 2.0 2.3 2.0 8.7 13.0 11.6 2.3 4.3 15.2 2.3 4.3 8.7 2.3 3.3 2.3 4.3

40 72 108 148 40 72 40 108 388 40 72 40 108 228 40 72 40 108 308

13 4 8 3.0 13 4 13 8 3.0 13 4 13 8 3.0 13 4 13 8 3.0

10 12 18 0 10 12 10 18 0 10 12 10 18 0 10 12 10 18 0

0.35 0.35 0.35 1.0 0.35 0.35 0.35 0.35 1.0 0.35 0.35 0.35 0.35 1.0 0.35 0.35 0.35 0.35 1.0

1.8 1.0 3.0 4.4 1.8 1.0 1.8 3.0 11.6 1.8 1.0 1.8 3.0 6.8 1.8 1.0 1.8 3.0 9.2

Table 13.23. Total requested dynamic head Pressure requested in lateral distal end Head loss in lateral Topographic difference Maximum friction head losses Control head losses Total 20 m 1.8 m 2m 14.1 m 8m 45.9 m

Comments a. The requested dynamic head relates to the most critical water delivery point.


b. The head losses could be decreased by 6 m head by choosing submains of larger diameter 140/6 mm. But since the water velocity in 110/6 mm pipes is lower than 2 m/sec it is doubtful if the increased pipe diameter is economically sensible. That depends on the cost of energy and has to be considered in respect to local circumstances. c. For sake of minimum head losses, two blocks will be irrigated per day: Day 1: blocks a + e Day 2: blocks b + f Day 3: blocks c + g Day 4: blocks d + h


14. MAINTENANCE OF MICRO IRRIGATION SYSTEMS 14.1. GeneralThe best system design cannot compensate for inadequate system maintenance. Micro irrigation systems in particular, require careful and strict maintenance. The narrow water passageways in the emitters, the widespread use of thin-wall laterals, the sensitivity of the filtration and fertigation devices, the buried underground emitters as well as the complexity of the monitoring and control appliances, require commitment to a meticulous maintenance policy. Maintenance actually begins with system installation. Improper installation will cause trouble throughout the system life span.

14.2. Critical Issues in Installation14.2.1. PVC PipesPVC pipes are prone to be damaged by sharp edges of stones or when exposed to expansion and contraction of heavy and compacted soils. Therefore, before laying PVC pipes in a trench, it should be padded with sand. Right angles in the pipeline must be supported by concrete casting to prevent disintegration of the pipeline.

14.2.2. LateralsWhen connecting laterals to manifolds, the barbed protrusion of the initial connector has to be fully inserted into the lateral to prevent the connectors from popping out in pressure surges.

Fig. 14.1. Punch (left) and holder (right) Courtesy "Netafim" Laterals laid from reels, have to be positioned leveled on the ground for several hours before they are connected and stabilized. The delay is necessary to accommodate the lateral and release twisting formed in the reel package.


Precise punching of holes in the lateral for insertion of on-line drippers and feeder tubes of micro-jets and micro-sprinklers, requires dedicated tools, as shown in fig. 14.1. Before initializing the system, laterals, manifolds and pipelines have to be thoroughly flushed, to wash out all debris and soil particles that penetrated into the system during installation work. In plots prone to woodpecker activity, subsurface drip irrigation is the preferred alternative; otherwise, woodpecker drippers can be installed.

14.3. Routine InspectionRoutine inspections and preventive measures are necessary to guarantee appropriate performance of the micro irrigation system. The best maintenance policy is to inspect the whole system periodically and systematically. Time intervals between inspections depend on water quality and the attributes of the system components. Inspections can be performed weekly, monthly, or twice a year in favorable conditions.

14.3.1. Pump InspectionIn self-pumping installations, pump efficiency has to be tested once in 5 years. When water contains sand particles and/or the water is corrosive, the test should be performed bi-annually. Pump efficiency below 75% is economically undesirable in contemporary high energy costs. Low efficiency may indicate the deterioration of pump components that if are not repaired or replaced promptly, may terminate pumping.

14.3.2. System PerformanceComparing the systems designed discharge to the actual flow rate provides preliminary indication of system performance. Deviation up to 10% is normal. A flow rate that is significantly lower than the designed discharge may indicate partial plugging of emitters or chocking of filters by dirt accumulation. A flow rate significantly higher than the designed may indicate burst pipelines or punching of pipes and laterals and water leakage. Deviation from the designed flow rate can also indicate changes in the pressure regime. The first step is to check the hourly flow rate at the main flow meter and compare it with the designed flow rate (number of emitters multiplied by the emitters nominal flow rate). Second step - the pressure gauges that are installed in the plot have to be checked. The measured values have to be compared to the designed pressure for each set. The pressure difference between inlet and outlet and dirt accumulation in filters have to be checked as well. When low flow rate is noticed in an appropriate pressure regime, on-farm inspection of emitter flow rate uniformity should be performed. The minimum number of emitters per sample is 20. The recommended number is 40-50. Once measured, the EU can be calculated and if it is unacceptable, the emitters should be cleaned with acid, flushed with pressurized air or replaced. The system should be checked again after treatment.


Visual indicators of inadequate system performance are random stressed plants, surface runoff, surfacing in SDI and white salt spots on the soil surface.

14.4 Routine Maintenance14.4.1. System Flushing and CleaningDuring irrigation, dirt, chemical precipitates and organic matter accumulate in the irrigation system. Most of the dirt accumulates in the distal ends of laterals, manifolds and pipelines. Before the first irrigation in the season, the system has to be flushed thoroughly. For proper dirt removal, flushing of laterals has to be sequential, one after another, to keep the appropriate pressure needed for Fig. 14.2. Automatic lateral end flushing valve adequate flow velocity in the open distal Courtesy "Netafim" end. The lateral end stopper is released and the dirty water is allowed to exit until clean water appears. Lateral flushing can be accomplished automatically by automatic flushing valves. In this case, flushing takes place in the initiation of the irrigation between water opening and the build-up of the operating pressure inside the lateral. Flushing velocities should be at least 0.5 to 0.6 m/s in order to remove effectively the dirt from the laterals. Flushing has to be performed several times per season. Intervals between flushing events depend on the rate of dirt accumulation.

14.4.2. Cleaning of Plugged DrippersWhen routine flushing is not sufficient to guarantee uniform emission, more drastic measures are required. Flushing with acid solution can dissolve lime and gypsum precipitates. Sulfuric, hydrochloric, phosphoric and nitric acids are used. The latter is the most potent agent but the most unsafe to use. Acids necessitate strict cautionary measures. In the case of unsuccessful acid treatment, the system can be flushed with high-pressure compressed air. Immersing the reels of retrieved laterals in an acidic solution for a few hours yields better results than flushing in the field. Sometimes, pressing the dripper carefully in a dry state can shatter the solid precipitates and enable them to be flushed out of the lateral. In certain compensating drippers, diaphragms lose their flexibility with time. Some diaphragms are sensitive to high concentrations of oxidizing agents like chlorine and bromine compounds.

14.4.3. Maintenance of Micro-jets and Micro-sprinklersIn distinction from drippers, malfunction of micro-jets and micro-sprinklers is easily noticed. The visual indications are changes in distribution patterns, an altered rotation rate in rotating emitters, stuck immobilized rotating and vibrating emitters and slanted stakes. Emitter-bearing stakes have to be positioned vertically. Stake bending impairs water distribution and may enhance run-off and water losses. 119

Certain stakes are marked to indicate the depth of insertion required to stabilize the emitter vertically and to ensure the emitter's right height above soil surface for optimal water distribution.

14.4.4. Maintenance of AccessoriesThe working environment of an irrigation system can be considered hostile. Chemical precipitations, friction-induced wear, corrosion and mucous excretions by microorganisms cooperate to hamper system performance. In the framework of routine maintenance, the functioning level of discrete components has to be checked routinely. Flow meters have to be calibrated once in 25 years, depending on the volume of water delivered and concentration of solid contaminants in the water. Most hydraulic valves have an internal diaphragm. The integrity and flexibility of the diaphragm has to be routinely inspected. If necessary, the diaphragm should be replaced. Pressure regulators operation mechanism is based on spring resistance or hydraulic equilibrium maintenance. Springs are weakened after prolonged operation. They should be inspected once in two years and replaced if necessary. Vacuum-relief valves carry out an important function in drip irrigation systems, particularly in sub-surface systems. When the irrigation is turned-off, water remaining in the system flows downhill to the lowest outlets. The water vacating the high points creates a vacuum, which causes the emitters in this Fig 14.3 Vertical section of the plot to suck in air and dirt. In extreme cases, stake PVC mainlines and thin-wall laterals may collapse. Vacuumrelief valves, installed at the high points in the system, are prone to clogging and need periodic inspection to ensure that no solid objects are caught inside and that they are not caught in an open or shut position. Air release valves also require the same periodic examination. The filtration system should be thoroughly inspected. In some filter types, the steel body is coated with epoxy paint to protect it from corrosion. The epoxy paint should be checked routinely. Cracks in the coating shorten the endurance of the entire body. The collectors of sand separators, should be purged periodically, otherwise excess accumulated sand will lower separation efficiency. Screen filters should be opened and screens visually inspected for wear, tear and blockage by organic matter, silt and chemical precipitates. The same applies to disk filters. Manually cleaned filters will be serviced when the pressure difference between the inlet and outlet exceeds 5 m. Automatic back-flushing filter systems require periodic visual inspection of the filtering elements against wear and presence of persistent contaminates. Backflushing filter components: control hydraulic valves, solenoids and rotating brushes or vacuum suckers, may require periodic servicing and lubrication. Most of them include


a small water filter to prevent blockage of solenoid ports and valve control chambers. This filter needs frequent manual cleaning. Automatic back-flushing media filters require special attention. They fluidize and resettle the filtering media with every flushing cycle. The discharge of back flushed media filters should be within the specified range of each model. For a typical 48" diameter tank, the range is 70 - 95 m3/h, higher than the filtering capacity of 50 70 m3. Below the lower margin, contaminants tend to infiltrate deeper into the media bed. Flow rates higher than the recommended upper threshold can lead to coning and canalization of the filtering media. To effectively back-flush a filter, an adequate flow rate is critical particularly for sand filtering media. It should be large enough to fluidize and lift the filtering media, while pushing out just only a minor amount of sand through the flushing discharge manifold. Media filters must be routinely inspected to check the height of the filtering media in the tank. During the back-flushing process, a portion of the media is drained-off. When the void tank volume is greater than of the total volume, the missing media should be replenished.

14.4.5. Maintenance of Fertigation systems Evaluating System PerformanceExcessive fertilization can induce salinity damage as well as antagonistic interference between nutrition elements. The precision of nutrient application can be checked in four procedures: a. Collecting water samples from the dripper laterals downstream from the injection point, and comparing the sample analysis with the desired concentration. b. Analyzing an extracted soil solution. c. Analyzing the nutrient content of soil samples. d. In detached beds it is common to collect drainage samples and compare them with samples of water collected from emitters. If the nutrient concentration of the drainage samples is significantly lower than the drippers emitted solution, the rate of the injected nutrients should be increased. The likelihood of leaching nutrients by excess water should also be examined. If nutrient level in drainage is higher than in the dripper emission, there may be excess nutrient injection or deficit in water application. Maintenance of Chemical Injection DevicesThe fertigation equipment is exposed to corrosive nutrient solutions. Metallic components like epoxy coated fertilizer tanks, injection pump components, controlling valves and pressure gauges corrode and should be replaced frequently. Some injection pumps have to be lubricated periodically. In diaphragm fertilizer pumps the diaphragm should be inspected for integrity and flexibility. Inflexible diaphragms will not perform perfectly.


14.5. Chemical Water TreatmentsChemical water treatments keep the system clean and running. They can be applied as a preventive measure or as a corrective treatment after the clogging occurred. The treatments can be classified into three groups: a. Acidification b. Oxidation c. Sterilization

14.5.1. AcidificationAcidification lowers water pH. This eliminates precipitation of insoluble salts of the cations calcium, magnesium, Iron and manganese with the anions bi-carbonate, carbonate, sulfate and phosphate. In low pH levels, the solubility of these salts is relatively high and the rate of precipitation is reduced significantly. The required concentration of the acid in irrigation water for attaining satisfactory results depends on the levels of bi-carbonates and sulfates in the water. The customary range is 0.5% - 1.5% in continuous acidification.

14.5.2. OxidationThe dominating oxidizing agents are diverse chlorine compounds. Oxidation is implemented for decomposing of sustained organic matter and preventing development of algae and colonies of microorganisms as persistent clogging factors. In water containing organic matter, iron, sulfur and manganese bacteria, routine oxidation with chlorine is obligatory. Chlorination can be accomplished continuously with 2 5 ppm of active chlorine in the water or intermittently as shock treatment when the build-up of slime in the system is accelerated. Shock treatment with 15 30 ppm chlorine is applied for 20 30 minutes. An upper threshold of 15 ppm is suggested to prevent damage to diaphragms in certain compensating emitters and hydraulic valves. A fast on-farm test indicates if the applied chlorine amount was sufficient. If the measured residual chlorine level in the distal ends of the laterals is above 0.5 1 ppm, sufficient chlorine had been applied. Copper sulfate is another oxidizing agent, particularly efficient in suppressing algae development in surface water reservoirs.

14.5.3. SterilizationSterilization is a specific treatment customary in sub-surface drip irrigation systems for eliminating root intrusion into the drippers. This is done by applying the chemical Trifluralin (TreflanTM). Treflan movement in the soil is negligible and restricts sterilization to the immediate vicinity of the dripper, thus preventing damage to the root system of the grown crop. The customary application regime is 2 4 applications per season. The frequent applications are given in coarse textured soils. The recommended amount per application is 125 mg per dripper. Injection time is 30 90 minutes, depending on lateral length. Use of Treflan impregnated drippers or filters can substitute its injection into the drip system.



Fig. 15.1. Nomogram for calculation of head losses in water flow in pipes


Fig. 15.2 Nomogram for calculation of head losses in LDPE pipes. Class designation relates to the working pressure (PN) in bar. 1 bar = 10 m Adapted from "Plassim" brochure


Fig. 15.3 Nomogram for calculation of head losses in HDPE pipes. The class designation relates to the working pressure (PN) in bar. 1 bar = 10 m. Adapted from "plassim" brochure


Fig. 15.4 Nomogram for calculation of head losses in PVC pipes. The class designation relates to the working pressure (PN) in bar. 1 bar = 10 m. Adapted from "Plastro" brochure 126

Fig. 15.5. Nomogram for calculation of local head losses in valves and other accessories and fittings


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Kuroda M. (2005) Planning and Designing of Micro irrigation in Humid Regions. International Commission on Irrigation and Drainage (ICID). Laemmlen, F. (1998). Proper Use of Drip Tape and Fertigation will Maximize Celery Yields. 624 West Foster Road, Suite A, Santa Maria, CA 93455. Lamm, F. R. (1998). Advantages and Disadvantages of Subsurface Drip Irrigation. Northwest Research-Extension Center, Kansas State University, Colby, Kansas. [email protected] Luke, G. And T. Calder. (2000). Blockages in Irrigation Lines. Division of Resource Management, South Perth, Department of Agriculture, Western Australia. Maas, E. V. (1984). Salt Tolerance in Plants. In: The Handbook of Plant Science in Agriculture. B.R. Christie (ed.). CRC Press, Boca Raton, Florida. Mahbub A., P. T. Todd, F. R. Lamm and D. H. Rogers. (1992). Filtration and Maintenance Considerations for Subsurface Drip Irrigation (SDI) Systems. Kansas State University Agricultural Experiment Station and Cooperative Extension Service Manhattan, Kansas. New Mexico State University Cooperative Extension Service, College of Agriculture and Home Economics (2001) Drip Irrigation for Row Crops Circular 573. Peacock, B. (2000). Amending Soil and Water Chemistry in Drip Irrigated Table Grape Vineyards. University of California, Tulare County, Cooperative Extension. Phene, C. J. (1999). Subsurface Drip Irrigation Part I: Why and How? Irrigation Journal, April 1999. Pitts, D. (1996). Field Evaluation of Micro Irrigation System Performance. SWFREC Report No. IMM-96-OO. Southwest Florida Research and Education Center, University of Florida, Immokalee, FL. Pitts, D. J., D. Z. Haman and A. G. Smajstrla. (1990). Causes and Prevention of Emitter Plugging In Micro Irrigation Systems. Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Poffley, M. (1997). Growing Vegetables Using Black Plastic Mulch and Trickle Irrigation. Agnote 367, Horticulture Division, Darwin. Reed, D.W. ed (1996). A Growers Guide to Water, Media and Nutrition for Greenhouse Crops. Ball Publishing, Batavia, Illinois. Russo, D, J. Zaidel, A. Laufer and Z. Gerstl (2001). Numerical Analysis of Transport of Trifluralin from a Subsurface Dripper. Soil Science Society of America Journal 65:1648-1658.Rust, M. And K. McArthur. (1998). Slow Sand Filtration. Water Treatment Primer. Environmental

Information Management, Civil Engineering Dept. Virginia Tech. Salgado, E. A. and M. A. Toro. (1995). Spatial Distribution of Avocado Roots under Drip and MicroSprinkler Irrigation. Proc. World Avocado Congress III, 1995 206 208 Sanders, D. C. (2001) Drip or Trickle Irrigation Systems: An Outline of Components. Department of Horticultural Science, College of Agriculture & Life Sciences North Carolina State University. Sanders, D. C. (2001). Drip or Trickle Irrigation Systems: An Operations and Troubleshooting Checklist. North Carolina State University. Sands G. (2001). Soil Water Concepts. University of Minnesota. Sanjines, A. and R. Ruskin (1991). Root Intrusion Protection for Subsurface Drip Emitters. ASAE paper No. 91-2047.


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Commercial Brochures and CD-ROMsAgridor Amiad Arad Ari Arkal Bermad Chapin-Watermatics Dorot Ein Tal Eldar-Shani Galcon Haifa IDE Irrometer Mezerplas NaanDan Netafim Plassim Odis Plastro Queen Gil Soil Moisture T-Tape Wade Rain


17. GLOSSARYAcidification: Increasing the acidity of a solution (including soil solution) by addition of hydrogen ions (by acids or acidic agents). Air Gap: A backflow preventing technique of physical separation or maintaining air gap between two piping systems or hydraulic devices. Allowable Depletion: The percentage from Plant Available Water (PAW) that can be depleted from the active plant root zone before irreversible damage is brought about to the plant. Anti-Siphon Valve: A control valve with a built-in atmospheric vacuum breaker. Atmospheric Vacuum Breaker: A backflow prevention device that introduces air into the irrigation system when the system pressure drops to atmospheric pressure or below, to prevent back siphonage. Back Pressure: Increase of pressure downstream above the pressure at the upstream side of the connection with the supply network that would cause a reversal of the flow direction. Back Siphonage: Reversal of water flow due to pressure reduction upstream, which generates a negative pressure below the downstream pressure in the system. Backflow: Reverse flow of water in a piping system. Backflush: reverse water flow through a filter, ion exchange column, or membrane intended to remove clogging particles. Booster Pump: A pump installed in the mainline inlet for increasing the pressure in the irrigation system when the pressure in the supply system is not high enough. Bulk Density: Mass per unit volume of undisturbed soil, dried to constant weight at 105 degrees C0 expressed as g/ml. Capillarity: Moisture movement in the soil in any direction through the fine pore spaces and as films around particles. The water is drawn into small diameter virtual tubes by the adhesive forces between the liquid and the tube walls. Chemigation: Application of chemicals like fertilizers, disinfectants, oxidizers, acidifiers, soil amendment agents and pesticides through the irrigation system. Coefficient of Uniformity (Cu): A measure of the uniformity of water distribution in a defined surface area, from emitters that deliver water through the atmosphere expressed as percentage. The CU is a comparison of the average precipitation of all catchment vessels and the deviation from that average. Crop Coefficient (Kc): The decimal fraction designating the ratio between a specific crop water requirement and the reference evapo-transpiration Et0. Deep Percolation: The vertical movement of water caused by gravity downward through the soil profile, below the root zone. Design Emission Uniformity: The anticipated emission uniformity relating to the emitters Cv and the expected pressure variation. Design Pressure: The minimum pressure required for proper operation of an irrigation system. Diameter of Coverage: Average diameter of the area wetted by emitter spreading water through the atmosphere in wind-less conditions. Diaphragms: Flexible membranes in automatic valves, fertilizer injectors and compensating emitters that regulates the passage of water through the device.


Double Check Valve (DCV): A device containing two independent, inline, positive seating, spring loaded check valves, two shut-off valves and ball valve test cocks. Drought: A period of dryness and insufficient soil moisture that causes extensive damage to crops and prevents their successful growth. Effective Rainfall: The amount of rain that is stored in the root zone. Electrical Conductivity: an indicator to the concentration of soluble salts in the soil solution. Elevation Gain: Pressure gained as water flows downhill from its source or a reference point. Encrustation (Soil Surface Sealing): The phenomenon in which the surface of a soil is compacted, dispersed and rearranged by the impact of raindrops. Although the surface seal is only few mm thick it dramatically reduces the infiltration rate of water. Erosion: The removal of soil particles from soil surface by weathering, running water, moving ice, wind and mass movement. Evapo-Transpiration (ET): The sum of the water amount lost through the evaporation of moisture from the soil and plant surface and the transpiration of water from the plant. Field Capacity: The percentage, per weight or per volume of the water retained in the soil after irrigation or rain when the rate of downward movement has substantially decreased, usually one to three days after irrigation or rain. Flush Flow: High initial momentary flow through a drip lateral required to flush the lateral and emitters before the working pressure is built-up. Hydraulic Conductivity: The rate at which water will move through soil in response to potential gradient. Infiltration (Intake) Rate: The dynamic rate at which irrigation or rain water applied to the soil surface will move into soil depth. The rate declines proportionally to the square root of time elapsed from the initial phase of surface hydration. Interception: The pattern and amount of precipitation that does not reach the soil surface due to blocking by the vegetation. Kilowatt-hour (KWh): A unit of electric power equivalent to the energy released by one thousand watts acting for one hour. Laminar Flow: Fluid flow that is characterized by straight flow lines in constant direction. In pipes it can be regarded as a series of liquid cylinders in the pipe, where the innermost ones are the fastest, and those near the pipe wall are the slowest. Mostly happens in low flow velocities. Leaching Requirement: the quantity of irrigation water required for removal of salts from the root zone to maintain a favorable salt balance for plant development. Maximum Allowed Depletion (MAD): The fraction of plant available water (PAW) that may be depleted from the active plant root zone without stress to the plant. Microclimate: Climate conditions in limited area that differ from the typical climate prevalent in the surrounding area. Micro-Sprayers: Inclusive designation of micro-jets, spinners, rotators, ray-jets, misters and foggers. Micro-Sprinklers: Miniature sprinklers discharging water in flow rate range of 20 200 l/hour. Mini-Sprinklers: Small sprinklers discharging water in flow rate range of 120 500 l/hour


Mulch: 1. Organic material applied to the soil surface to protect soil from raindrop impact, improve infiltration of rain, reduce runoff, evaporation from soil surface and soil temperature fluctuations. 2. Plastic sheets used to cover the soil surface for isolating the crop from the soil surface or to facilitate efficient soil fumigation under the sheets. Neutron Probe: An instrument used to estimate soil moisture by measuring the rate of attenuation in pulsated neutron emissions that depends on soil water content. Normally Closed Valve: An automatic valve through which no water will flow unless external actuation is applied that trigger the valve to open. Most electric valves are of the normally closed type. Normally Open Valve: An automatic valve through which water will flow unless external actuation is applied to close the valve. Most hydraulic valves are of the normally open type. Orifice: Discharge hole in an emitter or lateral. Ozonation: The process of applying ozone (O3) to a liquid for disinfection purpose. Pan Evaporation: Evaporative water losses from a standardized pan used to estimate crop evapotranspiration and assist in irrigation scheduling. Percent Area Wetted: The area wetted by irrigation as a percentage of the total area in the plot. Percolation Rate: The rate at which water moves through porous media, such as the soil. Permanent Wilting Point (PWP): The amount of water in the root zone, as percentage of the soil weight or volume at or below which the plant will permanently wilt without recovery. Plant Available Water (PAW): The amount of water held within the root zone after gravitational drainage has ceased, less the amount of water that adheres tightly to soil particles and defined as the permanent wilting point. Porosity: The percentage of the soil volume that is occupied by pore spaces. Potable Water: Water from any source that has been approved for human consumption, domestic or drinkable water by the authorized health agency. Pressure Relief Valve: A valve that will be opened when its inlet pressure exceeds a preset value. Pressure Vacuum Breaker (PVB): A backflow prevention device that introduces air into the system to prevent back siphonage. employs a spring loaded seat for positive opening to atmosphere. PSI: A pressure unit in the imperial unit system, Abbreviation for pounds per square inch. Pump Curve: A graphic representation of the performance of a pump correlating the rate of flow against the total head. The efficiency of the pump can be obtainable at selected points along the curve. Reduced Pressure Backflow Preventer (RPBP): A device consisting of two positive seating check valves, and an automatically operating pressure differential relief valve located between the two check valves. It is installed between two shut-off valves. RPBP protects from backflow caused by both backpressure and back siphonage. Reducer: A fitting used to change from certain pipe diameter to a smaller one. Reference Evapo-Transpiration (Et0) of Low Crops: Represents the rate of evapo-transpiration from an extensive surface of cool-season grass cover of uniform height of 12 cm, actively growing, completely shading the ground, and not short of water. Reference Evapo-Transpiration (Etr) of Medium Height Crops: represents the rate of evapotranspiration from an extensive surface of alfalfa or similar agricultural crop of uniform height of approximately 50 cm, actively growing, completely shading the ground, and not short of water. On the average ETr is 10% - 30% greater than ETo. 135

Regulated Deficit Irrigation (RDI): Irrigation management strategy where the plant root zone is not filled with water to field capacity level or the plant water requirement is not fully met. Residual Chlorine: The total amount of chlorine remaining in water, sewage, or industrial wastes at the end of a specified contact period following chlorination; expressed in ppm units. Runoff: The flow of water over the soil surface when rainfall (or irrigation) rate exceeds the infiltration rate of the soil. Runoff can detach and remove soil particles and thus cause erosion. Runtime: Length of time available to operate an irrigation system or an individual zone for a single irrigation event. Saturated Flow: The movement of water in saturated soil (when all the pores are filled with water). Snaking: Laying of loosened laterals to allow temperature induced contraction and elongation. Soil Auger: A metallic device used for drilling into the soil and removing soil samples for analysis. Soil Probe: A soil-coring tool that allows an intact soil core to be removed from the soil profile for examination. Soil Profile: A cross-section of the whole depth of the soil at a specific site, exposed by digging a soil pit. Solenoid Valve: An automatic valve actuated by electrical signals operates under low voltage (24v AC) which may be remotely actuated and controlled via a cable or wireless from the central controller. Solvent Welding: The act of chemically fusing pipe and fittings together using solvent and cement. Spaghetti Tubing: Small tubing used in drip and trickle systems to carry water from the lateral to the emitter and from the emitter to a specific plant. Substrate: A mineral or organic material that provides anchoring medium and reservoir of water and nutrients for the plants. Sub-Irrigation: applying irrigation water below the soil surface (or the growing bed) either by raising the water table into the root zone or by use of buried perforated or emitter bearing laterals. Surface Tension: The force acting on molecules at the surface of a liquid resulting from the attraction of the liquid molecules to each other. Surge: An energy wave in pipelines caused by abrupt opening or closing of valves. Throttle: A restriction of the cross-section of water passage in valves, pipes and other water passageways. Total Dissolved Solids (TDS) - A measure (in mg/l units) of the mineral salts that will be deposited after the water had completely evaporated. Total Dynamic Head (TDH): The sum of operation head, friction head and elevation head. The total energy that a pump must incorporate in the water to guarantee optimal function of the irrigation system. Total Suspended Solids (TSS): A measure of all suspended solids in a liquid, not including the dissolved salts, expressed in mg/l. Trajectory: The angle, relating to soil surface, of the water spattered out into the air from the emitter's nozzle. Transitional (Semi Turbulent) Flow: A mix of laminar and turbulent flow, with turbulence in the center of the pipe, and laminar flow near the walls. Each of these flows behaves in different manners in terms of their frictional energy loss while flowing.


Turbulent Flow: Flow pattern in which vortices, eddies and wakes make the flow unpredictable. The flow regime is characterized by random direction changes as well as rapid variation of pressure and velocity in space and time. Turbulent flow happens in general at high flow velocities and causes higher friction head losses than the same flow rate in laminar flow. U.P.V.C. Pipe: Unplasticized Polyvinyl Chloride pipe. Has better endurance and flexibility than ordinary PVC pipes. Water Hammer: The surging of pressure that occurs when a valve is suddenly closed or by high velocity of water flow. The surging may cause the pipes to vibrate or to burst in extreme circumstances. Water Use Efficiency (WUE): The amount of dry vegetal matter produced per unit of applied water. Expressed as g/m3 (grams of dry matter per m3 of applied water). Watering Window: The span of hours and days of the week that water is available for irrigation.