Principles And Practices Of Irrigation Management For .
AE260Principles and Practices of Irrigation Management forVegetables1M.D. Dukes, L. Zotarelli, G.D. Liu, and E.H. Simonne2This section contains basic information on vegetablewater use and irrigation management, along with somereferences on irrigation systems. Proper water managementplanning must consider all uses of water, from the sourceof irrigation water to plant water use. Therefore, it is veryimportant to differentiate between crop water requirementsand irrigation or production system water requirements.Crop water requirement refer to the actual water needs forevapotranspiration (ET) which are related to soil type andplant growth, and primarily depend on crop developmentand climatic factors which are closely related to climaticdemands. Irrigation requirements are primarily determinedby crop water requirements, but also depend on the characteristics of the irrigation system, management practices,and the soil characteristics in the irrigated area.soluble chemicals, proper irrigation management directlyaffects the efficacy of a BMP plan. The irrigation BMPs inthe “Water Quality/Quantity Best Management Practicesfor Florida Vegetable and Agronomic Crops” (accessible atwww.floridaagwaterpolicy.com) manual cover all major aspects of irrigation such as irrigation system design, systemmaintenance, erosion control, and irrigation scheduling.BEST MANAGEMENT PRACTICES(BMP) FOR IRRIGATIONBMPs have historically been focused on nutrient management and fertilizer rates. However, as rainfall or irrigationwater is the vector of off-site nutrient movement of nitratein solution and phosphate in sediments as well as otherFigure 1. Overhead Sprinkler irrigation with linear system.Credit: UF/IFAS Photography1. This document is AE260, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Date first printed: June 1995. Revised January2012. Please visit the EDIS website at http://edis.ifas.ufl.edu.2. M.D. Dukes, associate professor, Agricultural and Biological Engineering Department; L. Zotarelli, assistant research scientist, Agricultural andBiological Engineering Department; G. D. Liu, assistant professor, and E.H. Simonne, associate professor, Horticultural Sciences Department, UF/IFASExtension, Gainesville, FL 32611.The use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of the productsnamed, and does not signify that they are approved to the exclusion of others of suitable composition. Use pesticides safely. Read and follow directionson the manufacturer’s label.The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only toindividuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, nationalorigin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office.U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of CountyCommissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.
IRRIGATION WATER QUALITYCRITERIAUnderstanding irrigation water quality is critical forsustainability of vegetable production. In some areas ofFlorida, water quality impacts crop productivity morethan soil fertility, pest and weed control, variety, and otherfactors. Irrigation water quality is determined by thefollowing: (1) salinity hazard: total soluble salt content; (2)sodium hazard: ratio of sodium (Na ) to calcium (Ca2 )and magnesium (Mg2 ) ions; (3) water pH; (4) alkalinity:carbonate and bicarbonate; specific ions: chloride (Cl-),sulfate (SO42-), boron (BO3-), and nitrate-nitrogen (NO3-N);(5) organic contaminates: oil pollutants; and (6) otherfactors such as heavy metals. Among these factors, salinityis most significant particularly in those areas close to thecoast where salt content in ground water is frequently high.Irrigation water quality can be evaluated based on electricalconductivity (Table 1).Table 1. Suggested criteria for irrigation water quality based onelectrical conductivityEC2Concentration(TDS)1 Gravimetrictolerant to salinity stress. At 1 dS m-1, tomato yield increased with N rate but no yield response to N fertilizationat 5 dS m-1. However, carrot is rated as a sensitive crop. Rootyield declines 14% for every unit increase in salinity beyondthe threshold of 1 dS m-1. Therefore, irrigation managementfor vegetable production needs to be more careful. To avoidany accidental economic loss, before irrigating vegetablecrops, irrigation water quality should be checked based onelectrical conductivity with an appropriate salinity meterat least once a year, particularly in the near coastal areas.Vegetable growers may need to consult their extensionagent to interpret the results.Table 2. Threshold and zero yield salinity levels for four salinitygroups.Threshold SalinitySalinity RatingZero Yield SalinitydS/mSensitive1.48.0Moderately Sensitive3.016.0Moderately Tolerant6.024.0Tolerant10.032.0Available online at http://edis.ifas.ufl.edu/ae091ClassesWater quality(dS/m)4(PPM)3Class 1Excellent 0.25175Class 2Good0.25 - 0.75175-525Class 3Permissible50.76 - 2.00525-1400Class 4Doubtful2.01 - 3.001400-2100SpeciesClass 5Unsuitable6 3.002100Beans1.06.5Source: T.A. Bauder, R.M. Waskom and J.G. Davis. 2007. ColoradoState University Cooperative Extension Fact Sheet #: 0.506Also available online at 0TDS total dissolved solidsCantaloupe2.216.0EC electrical conductivityCarrot1.08.0PPM parts per millionCucumber2.510.0dS/m at 25 C mmhos/cmLettuce1.38.0Leaching needed if used.Onion1.27.5Good drainage needed and sensitive plants will have difficultyobtaining h2.015.0Sweet corn1.710.0Sweet potato1.510.5Tomato2.512.5Turnip0.912.0Zucchini squash4.715.06123456There are two main issues related to salinity: short term, i.e.,effect of water electrical conductivity on a particular cropand long term, namely, soil salinization. There is abundantbiodiversity in crop tolerance to salinity stresses (Tables2 and 3). Generally speaking, vegetable crops are moresusceptible than cereal crops.Also, different vegetable species differ significantly intolerance to salinity stress. For example, tomato is relativelyPrinciples and Practices of Irrigation Management for VegetablesTable 3. Salinity level (dS/m) of irrigation water for 100%productivity (zero yield loss) or zero productivity (zero yield) invegetable productionZero yield lossZero yieldSalinity level (dS/m)After Ayers and Wescott, 1985. Available online at http://edis.ifas.ufl.edu/ae0912
USES OF IRRIGATION WATERIrrigation systems have several uses in addition to waterdelivery for crop ET. Water is required for a preseasonoperational test of the irrigation system to check for leaksand to ensure proper performance of the pump and powerplant. Irrigation water is also required for field preparation,crop establishment, crop growth and development, withinseason system maintenance, delivery of chemicals, frostprotection, and other uses such as dust control.Field PreparationField preparation water is used to provide moisture to thefield soil for tillage and bed formation. The water used forfield preparation depends on specific field cultural practices, initial soil moisture conditions, the depth to the naturalwater table, and the type of irrigation system. Drip-irrigatedfields on sandy soils often require an additional irrigationsystem for field preparation because drip tubes are notinstalled until the beds are formed. Many drip irrigatedvegetable fields may also require an overhead or subirrigation system for field preparation. However, sprinklerirrigation systems can meet different water requirements.For example, sprinkler irrigation systems installed in manystrawberry production fields can work for both irrigationand frost protection. These systems are also used for fieldpreparation and may apply one or more in. of water for thispurpose. Subirrigated fields use the same system for fieldpreparation as well as for crop establishment, plant growthneeds, and frost protection. Subirrigation water management requirements depend on the soil characteristicswithin the irrigated field and surrounding areas. Sufficientwater must be provided to raise the water table level as highas 18 to 24 in. below the soil surface. Water is required tofill the pores of the soil and also satisfies evaporation andsubsurface runoff requirements. As a rough guide, 1.0 to2.5 in. of water are required for each foot of water table rise.For example, a field with a pre-irrigation water table 60 in.deep may need about 2 in. of water to raise the water tableto 18 in., while a pre-irrigation water table at 48 in. mayrequire 5 in. of water for the same result.Crop EstablishmentVegetables that are set as transplants, rather than directseeded require irrigation for crop establishment in excess ofcrop ET. Establishment irrigations are used to either keepplant foliage wet by overhead sprinkler irrigation (to avoiddesiccation of leaves) or to maintain high soil moisturelevels until the root systems increase in size and plantsstart to actively grow and develop. Establishment irrigation practices vary among crops and irrigation systems.Principles and Practices of Irrigation Management for VegetablesStrawberry plants set as bare-root transplants may require10 to 14 days of frequent intermittent overhead irrigationfor establishment prior to irrigation with the drip system.The amount of water required for crop establishment canrange widely depending on crop, irrigation system, andclimate demand. Adequate soil moisture is also needed forthe uniform establishment of direct-seeded vegetable crops.Crop Growth and DevelopmentIrrigation requirements necessary to meet the ET needs ofa crop depend on the type of crop and growth stage, fieldsoil characteristics, irrigation system type and capacity.Different crops vary in growth characteristics that result indifferent relative water use rates. Soils differ in texture andhydraulic characteristics such as available water-holdingcapacity (AWHC) and capillary movement. Because sandsgenerally have very low AWHC values (3% to 6% is common), a 1% change in AWHC affects irrigation practices.Water Application (IrrigationRequirement)Irrigation systems are generally rated with respect to application efficiency (Ea), which is the fraction of the waterthat has been applied by the irrigation system and that isavailable to the plant for use (Table 4). Applied water thatis not available to the plant may have been lost from thecrop root zone through evaporation or wind drifts of spraydroplets, leaks in the pipe system, surface runoff, subsurfacerunoff, or deep percolation within the irrigated area.Irrigation requirements (IR) are determined by dividingthe desired amount of water to provide to the plant (ETc),by the Ea as a decimal fraction (Eq.[1]). For example, if itis desired to apply 0.5 in. to the crop with a 75% efficientsystem, then 0.5/0.75 0.67 in. would need to be pumped.Hence, when seasonal water needs are assessed, the amountof water needed should be based on the irrigation requirement and all the needs for water, and not only on the cropwater requirement. For more information, consult IFASbulletin 247 “Efficiencies of Florida agricultural irrigationsystems” (http://edis.ifas.ufl.edu/AE110) and bulletin 265“Field evaluation of microirrigation water applicationuniformity” (http://edis.ifas.ufl.edu/AE094). Catch cans canbe used in the field to measure the actual amount of waterapplied.Eq. [1] Irrigation requirement Crop water requirement / Application efficiencyIR ETc/Ea3
Table 4. Application efficiency for water delivery systems usedin FloridaIrrigation system Application efficiency (Ea)Overhead60-80%Seepage20-70%Drip280-95%1Ea greater than 50% are not expected unless tailwater recovery isused1With or without plastic mulch2Fertigation/ChemigationIrrigation systems are often used for delivery of chemicalssuch as fertilizers, soil fumigants, or insecticides. The cropmay require nutrients when irrigation is not required, e.g.after heavy rainfall. Fertilizer injection schedules basedon soil tests results are provided in each crop productionchapter of this production guide. Fertigation should notbegin until the system is pressurized. It is recommendedto always end a fertigation/chemigation event with a shortflushing cycle with clear water to avoid the accumulation offertilizer or chemical deposits in the irrigation system, and/or rinse crop foliage. The length of the flushing cycle shouldbe 10 minutes longer than the travel time of the fertilizerfrom the irrigation point to the farthest point of the system.System MaintenanceIrrigation systems require periodic maintenance throughout the growing season. These activities may require systemoperation during rainy periods to ensure that the systemis ready when needed. In addition, drip-irrigation systemsmay require periodic maintenance to prevent cloggingand sys-tem failure. Typically, cleaning agents are injectedweekly, but in some instances more frequent injections areneeded.Frost ProtectionFor some crops, irrigation is used for frost protectionduring winter growing seasons. For strawberry production,sprinkler irrigation is primarily used with application ratesof about 0.25 in. per hour during freeze events. Waterfreezes at 32ºF, while most plant tissues freeze at lowertemperatures. Overhead freeze protection is efficient forair temperature as low as 26ºF-28ºF, but seldom below. Forvegetable fields with subirrigation systems, the relativelyhigher temperature of groundwater can be used for coldprotection. Growers may also irrigate to raise the watertable throughout the field. Frost protection water requirements vary and depend on the severity and duration offreeze events, the depth to the existing water table level,and field hydraulic characteristics. For more information,consult IFAS bulletin HS931 “Microsprinkler Irrigation forPrinciples and Practices of Irrigation Management for VegetablesCold Protection of Florida Citrus” (http:// http://edis.ifas.ufl.edu/ch182) and bulletin SL296 “Citrus Cold WeatherProtection and Irrigation Scheduling Tools Using FloridaAutomated Weather Network (FAWN) Data” (http://edis.ifas.ufl.edu/ss509).Other UsesOther irrigation uses vary according to the type of crop,system characteristics, and field location. Some examplesinclude: periodic overhead irrigation for dust control;wetting of dry row middles to settle dust and preventsand from blowing during windy conditions; and wettingof roadways and drive aisles to provide traction of farmvehicles.IRRIGATION SCHEDULINGA wide range of irrigation scheduling methods is used inFlorida, with corresponding levels of water management(Table 5). The recommended method (level 5) for scheduling irrigation (drip or overhead) for vegetable crops isto use together: the crop water requirement method thattakes into account plant stage of growth associated withmea-surements of soil water status, and guidelines forsplitting irrigation (see below). A typical irrigation schedulecon-tains (1) a target crop water requirement adjustedto crop stage of growth and actual weather demand, (2)adjustment of irrigation application based on soil moisture,(3) a rule for splitting irrigation, (4) a method to accountfor rainfall, and (5) record keeping (Table 6). For seepageirrigation, the water table should be maintained near the18-in. depth (measured from the top of the bed) at plantingand near the 24-in. depth when plants are fully grown.Water tables should be maintained at the proper level toensure optimum moisture in the bed without leading tooversatu-ration of the root zone and potential losses ofnutrients. Water tables can be monitored with a section ofPVC pipe sunk in the soil with a calibrated float inside thePVC pipe. The calibrated float can be used to determine theexact level of the water table.4
Table 5. Levels of water management and corresponding irrigation scheduling methodWaterIrrigation scheduling methodMgt. Level0Guessing (irrigate whenever), not recommended1Using the ”feel and see” method, see lmoist.pdf2Using systematic irrigation (Example: ¾ in. every 4th day, or 2 hrs every day)3Using a soil water tension measuring tool or soil moisture sensor to start irrigation4Schedule irrigation and apply amounts based on a budgeting procedure and checking actual soilwater status51Adjusting irrigation to plant water use (ETo), and using a dynamic water balance based on abudgeting procedure and plant stage of growth, together with using a soil water tension measuringtool or soil moisture sensorRecommended method1Table 6. Summary of irrigation scheduling guidelines for vegetable crops grown in FloridaIrrigation system1Irrigationscheduling componentSeepage2Drip31- Target water application rateKeep water table between 18- and 24-in. depthHistorical weather data or crop evapotranspiration(ETc) calculated from reference ET or Class A panevaporation2- Fine tune application with soil Monitor water table depth with observation wellsmoisture measurementMaintain soil moisture level in the root zonebetween 8 and 15 cb (or 8% and 12% available soilmoisture)3- Determine the contributionof rainfallTypically, 1 in. rainfall raises the water table by 1 footPoor lateral water movement on sandy and rockysoils limits the contribution of rainfall to crop waterneeds to (1) foliar absorption and cooling of foliageand (2) water funneled by the canopy through theplan hole.4- Rule for splitting irrigationNot applicable. However, a water budget can bedevelopedIrrigations greater than 12 and 50 gal/100 ft (or 30min and 2 hrs for drip tapes with medium flow-rate)when plants are small and fully grown, respectivelyare likely to push the water front below the rootzone5-Record keepingIrrigation amount applied and totalrainfall received4Irrigation amount applied and total rainfallreceived4Days of system operationDaily irrigation scheduleEfficient irrigation scheduling also requires a properly designed and maintained irrigation system1Practical only when a spodic layer is present in the field2On deep sandy soils3Required by the BMP4Principles and Practices of Irrigation Management for Vegetables5
Soil Water Status, Soil Water Tension andSoil Volumetric Water ContentGenerally, two types of sensors may be used for measurements of soil water status, those that measure soil waterpotential (also called tension or suction) and those thatmeasure volumetric water content directly. Soil watertension (SWT) represents the magnitude of the suction(negative pressure) the plant roots have to create to free soilwater from the attraction of the soil, and move it into theroot cells. The dryer the soil, the higher the suction needed,hence, the higher SWT. SWT is commonly expressed incentibars (cb) or kilopascals (kPa; 1cb 1 kPa; 7 kPa 1psi). For most vegetable crops grown on the sandy soilsof Florida, SWT in the rooting zone should be maintainedbetween 6 (slightly above field capacity) and 15 cb. Becauseof the low AWHC of Florida soils, most full-grownvegetable crops will need to be irrigated daily. During earlygrowth, irrigation may be needed only two to three timesweekly. SWT can be measured in the field with moisturesensors or tensiometers. For more information on SWTmeasuring devices, consult IFAS circular 487 “Tensiometersfor Soil Moisture Measurement and Irrigation Scheduling”available at http://edis.ifas.ufl.edu/ae146 and bulletin 319“Tensiomete
Principles and Practices of Irrigation Management for Vegetables 3 USES OF IRRIGATION WATER Irrigation systems have several uses in addition to water delivery for crop ET. Water is required for a preseason operational test of the irrigation system to check for leaks and to ensure proper performance of the pump and power plant.
The Irrigation Requirement is the Crop Water Requirement after taking into account the irrigation efficiency and, for drip systems, the drip factor: IR CWR * Df / Ie For irrigation systems other than drip, the drip factor 1. 6. Irrigation Water Demand (IWDperc and IWD) The portion of the Irrigation Water Demand lost to deep percolation is .
Chapter 9 Irrigation Water Management Part 652 Irrigation Guide (210-vi-NEH 652, IG Amend. NJ1, 06/2005) NJ9-1 NJ652.09 Irrigation Water Management (a) General Irrigation water management is the act of timing and regulating irrigation water applications in a way that will satisfy the
SMART IRRIGATION: THE CONCEPT Automatically adjust irrigation run times in response to environmental changes A well-designed 'smart irrigation'system can be 95% efficient matching actual daily plant water requirements to realise water use savings of 40%. Household water use for garden irrigation reduced Water used for POS and verge irrigation
Technical Guideline for Design of Irrigation Canal and Related Structures May, 2014 The Project for Capacity Building in Irrigation Development (CBID) Foreword Oromia Irrigation Development Authority (OIDA) is established on June, 2013, as a responsible body for all irrigation development activities in the
The Irrigation Caddy (IC) device is an Ethernet irrigation system. The system allows the user to control and schedule an irrigation system from any computer with a web browser.File Size: 679KB
rate of infusion and how long continuous irrigation will be needed. 3. Note expiration date of irrigant solution. 4. Irrigation tubing should be changed every 48 hours. 5. Be sure that irrigation tubing fits correctly into irrigation solution container. EQUIPMENT: Irrigation solution Irrigatio
Overhead Systems (Sprinklers, Centre Pivot, Linear, Traveling gun, Rotating boom) Drip Micro sprinkler Flood irrigation (basins and beds) Flood irrigation (narrow furrows) Flood irrigation (wide furrows) Flood irrigation (alternative furrows) 100 100 30 - 40 40 - 80 80 - 100 60 - 100 40 - 60 30 - 50 1.4 System Efficiency
MOSARIM No.248231 2012-12-21 File: D.6.1.1.final_report_final.doc 8/21 from Frost&Sullivan, ABI research and Techno Systems Research overall market penetration and percentage of newly radar equipped vehicles per year were forecasted until 2020, as shown in Figure 7. It has to be noted that the given numbers are not necessarily in agreement
