micro irrigation

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  • M.M.Palitha Mahinda Munasinghe

    [email protected]

    A scientific method of irrigation carrying desired water and nutrients direct to the root zone of the plant.*

  • Depiction 11/08/2007*mmpmmDelivery of water at low flow rates through various types of water applicators Through Emitters, Spray Nozzles, or porous tubeLocated on the soil surface, beneath the surface, or above the groundWater is applied as drops, tiny streams, or spray

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  • 11/08/2007*mmpmmCharacteristics of Water ApplicationLow ratesOver long periods of timeAt frequent intervalsNear or directly into the root zoneAt low pressureUsually maintain relatively high water contentUsed on Higher value agricultural/horticultural crops Landscapes and nurseries

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  • 11/08/2007*mmpmmAdvantages of Micro irrigationHigh application efficiencyHigh yield/qualityDecreased energy requirementsReduced salinity hazardAdaptable for chemigation/FertigationReduced weed growth and disease problemsCan be highly automated

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  • 11/08/2007*mmpmmHigh initial costMaintenance requirements (emitter clogging, etc.)Restricted plant root developmentSalt accumulation near plants (along the edges of the wetted zone)

    Limitation of Micro irrigation

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  • 11/08/2007*mmpmmTypes of SystemsSurface trickle (drip)

    Water applied through small emitter openings to the soil surface (normally less than 3 gal/hr per emitter)Most prevalent type of micro irrigationCan inspect, check wetting patterns, and measure emitter discharges

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  • 11/08/2007*mmpmmTypes of Systems SprinklerWater applied (spray, jet, fog, mist) to the soil surface at low pressure (normally less than about 1 gal/min per spray applicator)Aerial distribution of water as opposed to soil distributionReduced filtration and maintenance requirements because of higher flow rate

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  • 11/08/2007*mmpmmBubblerWater applied as a small stream to flood the soil surface in localized areas (normally less than about 1 gal/min per discharge point)Application rate usually greater than the soil's infiltration rate (because of small wetted diameter)Minimal filtration and maintenance requirements

    Types of Systems Bubbler irrigation is not usual in agricultural irrigation ,typically apply water on a 'per plant' basis

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  • 11/08/2007*mmpmmSubsurface trickleWater applied through small emitter openings below the soil surfaceBasically a surface system that's been buried (few inches to a couple feet)Permanent installation that is "out of the way"

    Types of Systems

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  • 11/08/2007*mmpmmSchematic of a Micro irrigation System

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  • 11/08/2007*mmpmmPumpControl headFiltersChemical injection equipment (tanks, injectors, backflow prevention, etc.)Flow measurement devicesValvesControllersPressure regulatorsMainlines and Sub mains (manifolds)Plastic (PVC)LateralsPlastic (PE)With or without emitters

    System Components

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  • Applicator HydraulicsGeneralNeed pressure in pipelines to distribute water through the system, but the applicator needs to dissipate that pressureqe =KHx

    qe = emitter dischargeK = emitter discharge coefficientH = pressure head at the emitterX = emitter discharge exponent (varies with emitter type)

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  • 11/08/2007*mmpmmRequires discharges qe1 , qe2 at two pressures h1, h2Emitter Coefficient

    orEmitter Exponent

    Estimating Emitter Exponent & Coefficient

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  • 11/08/2007*mmpmmApplicator Hydraulics ContEmitters (Point Source)Long-pathOrificeVortexPressure compensating (x < 0.5)FlushingLine-source tubingPorous-wall tubing (pores of capillary size that ooze water)Single-chamber tubing (orifices in the tubing or pre-inserted emitters)Double-chamber tubing (main and auxiliary passages)

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  • 11/08/2007*mmpmmSprayersFoggers, Splitters, Misters, etcRelatively uniform application over the wetted areaLateral hydraulicsVery much like sprinkler hydraulics, but on a smaller scaleUsually a large number of emitters, multiple outlet factor (F) 0.35

    Applicator Hydraulics Cont

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  • 11/08/2007*mmpmmCloggingPhysical (mineral particles)Chemical (precipitation)Biological (slimes, algae, etc.)FiltrationSettling basinsSand separators (centrifugal or cyclone separators)Media (sand) filtersScreen filters

    Other Design and Management Issues

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  • 11/08/2007*mmpmmSize: 2", 3", 4" Flux: 30-70 L/H Different types of filtration systems The type is dictated by the water source and also by emitter size

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  • Filter openings should be 1/7th 1/10th the size of the emitter orifice0.020-inch orifice

    11/08/2007*mmpmmFiltration Requirements for Drip Emitters

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  • 11/08/2007*mmpmmChemical treatmentAcid: prevent calcium precipitationChlorineControl biological activity: algae and bacterial slimeDeliberately precipitate ironFlushingAfter installation or repairs, and as part of routine maintenanceValves or other openings at the end of all pipes, including lateralsApplication uniformityManufacturing variationPressure variations in the mainlines and lateralsPressure-discharge relationships of the applicators

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  • 11/08/2007*mmpmmHigh water application efficiencyUniform water applicationLow pressure & power requirementsAdaptable to any field shapeNo dry corners (vs. center pivot)Adaptable to automation

    Advantages of Sub-surface Drip Irrigation

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  • 11/08/2007*mmpmmHigh initial costWater filtration requiredComplex maintenance requirementsFlushing, Chlorination, Acid injectionSusceptible to gopher damageSalt leaching limitations

    Disadvantages of Subsurface Drip Irrigation

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  • 11/08/2007*mmpmmSubsurface Drip-Center Pivot Comparison(-Section Field; ET = 0.25 in/day)

    Subsurface DripCenter PivotArea Irrigated160 acres125 acresInitial CostRs.800-1000/acreRs.280-360/acreIrrigation Efficiency90-95%70-85%Water Requirement5.0-5.3 gpm/acre5.5-6.8 gpm/acreOperating Pressure10-20 psi25-35 psiEnergy Requirement(250-ft lift, mile supply line)36 hp-hr/ac-in48 hp-hr/ac-in

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  • Emitter SpacingEmitter Discharge11/08/2007*mmpmmSubsurface Drip Irrigation Water Application Rates(inches/hour)(60`` tube spacing)

    12 inches18 inches24 inches0.16 gph0.0430.0340.0260.21 gph0.0560.0450.0340.33 gph0.0880.0710.0530.53 gph0.1420.1130.085

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  • Turbulent flow PVC emitter welded inside tubing16-mm diameter, seamless, 13-mil thick extruded PE tubingEmitter outlet11/08/2007*mmpmmDrip Irrigation Tube

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  • Flap over emitter outlet- prevents root intrusion- prevents blockage by mineral scale11/08/2007*mmpmmDrip Irrigation Tube (in line)

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  • 30 in60 inSubsurface Drip Tube Installation for Row Crops12 14 inNon Wheel- Track RowWetting PatternDrip Tubing60`` drip line spacing is satisfactory on silt loam & clay loam soils11/08/2007*mmpmm

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  • 11/08/2007*mmpmmPlowing For Laying Drip Tubes

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  • 11/08/2007*mmpmmTrenching across the drip tube ends for PVC manifold installation

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  • 11/08/2007*mmpmmDrip Tube Installation for Row Crops

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  • Drip tube end after being sheared by the trencher11/08/2007*mmpmm

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  • 11/08/2007*mmpmmComponents for Drip Lateral & Sub-main Connection

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  • 11/08/2007*mmpmmDrip tube Connect to Sub-main tube

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  • 11/08/2007*mmpmmDual acting valve for air release and vacuum relief automaticallyComponents for Drip Lateral & Sub-main Connection

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  • 11/08/2007*mmpmmLateral flushing schedule (sediment)Chlorine injection schedule (biological growths)Acid injection schedule (chemical precipitates & scaling)

    Subsurface Drip Irrigation System Maintenance

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  • Salt Movement Under Irrigation with Saline WaterSalt accumulation leached downward by successive water applicationsSalt accumulation leached radials outward from drip tubeSubsurface DripSprinkler/Flood11/08/2007*mmpmm

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    A scientific method of irrigation carrying desired water and nutrients direct to the root zone of the plant.*

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