Micro irrigation
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Transcript of Micro irrigation
Depiction Depiction
11/08/2007 2mmpmm
Delivery 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
11/08/2007 3mmpmm
Characteristics of Water ApplicationCharacteristics 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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Advantages of Advantages of Micro irrigationMicro irrigation
High application efficiencyHigh yield/qualityDecreased energy requirementsReduced salinity hazardAdaptable for chemigation/FertigationReduced weed growth and disease problemsCan be highly automated
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High initial costMaintenance requirements (emitter clogging, etc.)Restricted plant root developmentSalt accumulation near plants (along the edges of the
wetted zone)
Limitation of Limitation of Micro irrigationMicro irrigation
11/08/2007 6mmpmm
Types of SystemsTypes of Systems
Surface 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
11/08/2007 7mmpmm
Types of Systems …Types 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 distribution
Reduced filtration and maintenance requirements Reduced filtration and maintenance requirements because of higher flow ratebecause of higher flow rate
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BubblerWater 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 …Types of Systems …
Bubbler irrigation is not usual in agricultural irrigation ,typically apply water on a 'per plant' basis
11/08/2007 9mmpmm
Subsurface 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 …Types of Systems …
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Schematic of a Micro irrigation SystemSchematic of a Micro irrigation System
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Pump Control head
FiltersChemical injection equipment (tanks, injectors, backflow
prevention, etc.)Flow measurement devicesValvesControllers
Pressure regulatorsMainlines and Sub mains (manifolds)
Plastic (PVC)Laterals
Plastic (PE)With or without emitters
System ComponentsSystem Components
Applicator HydraulicsApplicator HydraulicsGeneral
Need pressure in pipelines to distribute water through the system, but the applicator needs to dissipate that pressure
qe =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 13mmpmm
Emitter TypeEmitter Type
Coefficient, K - Exponent, XCoefficient, K - Exponent, X
Emitter Discharge, gpmEmitter Discharge, gpm
Operating PressureOperating Pressure
8 psi8 psi 12 psi12 psi 16 psi16 psi
Porous Pipe - 0.112 Porous Pipe - 0.112 1.001.00
2.072.07 3.13.1 4.144.14
Tortuous Path 0.112 Tortuous Path 0.112 0.650.65
0.750.75 0.970.97 1.171.17
Vortex/Orifice 0.112 Vortex/Orifice 0.112 0.420.42
0.380.38 0.450.45 0.510.51
Compensating 0.112 Compensating 0.112 0.200.20
0.200.20 0.220.22 0.230.23
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11/08/2007 15mmpmm
Requires discharges qe1 , qe2 at two pressures h1, h2
Emitter Coefficient
oror
Emitter Exponent
Estimating Emitter Exponent & Coefficient Estimating Emitter Exponent & Coefficient
11/08/2007 16mmpmm
Applicator Hydraulics Cont…Applicator Hydraulics Cont…
Emitters (Point Source)Long-pathOrificeVortexPressure compensating (x < 0.5)Flushing
Line-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)
11/08/2007 17mmpmm
SprayersFoggers, Splitters, Misters, etcRelatively uniform application over the wetted area
Lateral hydraulicsVery much like sprinkler hydraulics, but on a smaller scaleUsually a large number of emitters, multiple outlet factor
(F) 0.35
Applicator Hydraulics Cont…Applicator Hydraulics Cont…
11/08/2007 18mmpmm
CloggingPhysical (mineral particles)Chemical (precipitation)Biological (slimes, algae, etc.)
FiltrationSettling basinsSand separators (centrifugal or cyclone
separators)Media (sand) filtersScreen filters
Other Design and Management Issues
11/08/2007 19mmpmm
Size: 2", 3", 4" Flux: 30-70 L/H
Different types of filtration systems Different types of filtration systems
The type is dictated by the water source and also by emitter size
Filter openings should be 1/7th – 1/10th the size
of the emitter orifice
0.020-inch orifice
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Filtration Requirements for Drip Filtration Requirements for Drip EmittersEmitters
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Chemical treatmentAcid: prevent calcium precipitationChlorine
Control biological activity: algae and bacterial slimeDeliberately precipitate iron
FlushingAfter installation or repairs, and as part of routine
maintenanceValves or other openings at the end of all pipes, including
lateralsApplication uniformity
Manufacturing variationPressure variations in the mainlines and lateralsPressure-discharge relationships of the applicators
11/08/2007 23mmpmm
High water application efficiencyUniform water applicationLow pressure & power requirementsAdaptable to any field shapeNo dry corners (vs. center pivot)Adaptable to automation
Advantages of Sub-surface Advantages of Sub-surface Drip Irrigation Drip Irrigation
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High initial costWater filtration requiredComplex maintenance requirementsFlushing, Chlorination, Acid injectionSusceptible to gopher damageSalt leaching limitations
Disadvantages of Subsurface Disadvantages of Subsurface Drip Irrigation Drip Irrigation
11/08/2007 25mmpmm
Subsurface Drip Center PivotArea Irrigated 160 acres 125 acres
Initial Cost Rs.800-1000/acre Rs.280-360/acre
Irrigation Efficiency 90-95% 70-85%
Water Requirement 5.0-5.3 gpm/acre 5.5-6.8 gpm/acre
Operating Pressure 10-20 psi 25-35 psi
Energy Requirement(250-ft lift, ¼ mile supply line)
36 hp-hr/ac-in 48 hp-hr/ac-in
Subsurface Drip-Center Pivot ComparisonSubsurface Drip-Center Pivot Comparison(¼-Section Field; ET = 0.25 in/day)(¼-Section Field; ET = 0.25 in/day)
Emitter Spacing
Emitter Discharge
11/08/2007 26mmpmm
Subsurface Drip Irrigation Water Application Rates(inches/hour)
(60`` tube spacing)12 inches 18 inches 24 inches
0.16 gph 0.043 0.034 0.026
0.21 gph 0.056 0.045 0.034
0.33 gph 0.088 0.071 0.053
0.53 gph 0.142 0.113 0.085
11/08/2007 27mmpmm
Schematic of Subsurface Drip Irrigation (SDI) System
Pump Station
BackflowPrevention
Device
Flowmeter
Chemical Injection System
Air & VacuumRelease Valve
X X
Pressure Gage
X X
Flush Valve
XX
Dripline Laterals
Zones1 and 2
Submain
Flushline
Filtration System
x
X Zone Valve
Turbulent flow PVC emitter welded inside tubing
16-mm diameter, seamless, 13-mil thick extruded PE tubing
Emitter outlet
11/08/2007 28mmpmm
Drip Irrigation TubeDrip Irrigation Tube
Flap over emitter outletFlap over emitter outlet- prevents root intrusion- prevents root intrusion- prevents blockage by mineral - prevents blockage by mineral scale scale
11/08/2007 29mmpmm
Drip Irrigation Tube (in line)Drip Irrigation Tube (in line)
30 in
60 in60 in
Subsurface Drip Tube Installation for Row Subsurface Drip Tube Installation for Row CropsCrops
12 – 14 in12 – 14 in
Non Wheel- Track Row
Wetting PatternWetting Pattern
Drip TubingDrip Tubing
60`` drip line spacing is satisfactory on silt loam & clay loam soils11/08/2007 30mmpmm
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Plowing For Laying Drip Tubes
11/08/2007 32mmpmm
Trenching across the drip tube Trenching across the drip tube ends for PVC manifold installationends for PVC manifold installation
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Drip Tube Installation for Row CropsDrip Tube Installation for Row Crops
Drip tube end after being sheared by the Drip tube end after being sheared by the trenchertrencher
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21/32” Hole in Sub-main21/32” Hole in Sub-main
GrommetGrommet
Polyethylene Polyethylene Barb AdapterBarb Adapter
5/8” Polyethylene5/8” Polyethylene
Stainless Steel Wire Twist TieStainless Steel Wire Twist Tie
5/8” Drip Irrigation Tubing5/8” Drip Irrigation Tubing11/08/2007 35mmpmm
Components for Drip Lateral & Sub-main ConnectionComponents for Drip Lateral & Sub-main Connection
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Drip tube Connect to Sub-main tubeDrip tube Connect to Sub-main tube
From Sub main or to Flushing From Sub main or to Flushing manifoldmanifold
Grommet Inserted in Grommet Inserted in 21/32” hole in 21/32” hole in manifoldmanifold
Polyethylene Polyethylene Barb Adapter Barb Adapter Inserted in Inserted in GrommetGrommet
5/8” 5/8” Polyethylene Polyethylene Supply TubeSupply Tube
5/8” Drip 5/8” Drip Irrigation TubeIrrigation Tube
Stainless Steel Stainless Steel Wire Twist TieWire Twist Tie
11/08/2007 37mmpmm
Dual acting valve for air release and vacuum relief automatically
Components for Drip Lateral & Sub-main ConnectionComponents for Drip Lateral & Sub-main Connection
11/08/2007 38mmpmm
Lateral flushing schedule (sediment)Chlorine injection schedule (biological
growths)Acid injection schedule (chemical precipitates
& scaling)
Subsurface Drip Irrigation System Maintenance
Salt Movement Under Irrigation with Saline WaterSalt Movement Under Irrigation with Saline Water
Salt accumulation leached downward by successive water
applications
Salt accumulation leached radials outward from drip tube
Subsurface Drip Sprinkler/Flood
11/08/2007 39mmpmm
