MicroirrigationMicroirrigation

MicroirrigationMicroirrigation

• Delivery of water at low flow rates Delivery of water at low flow rates through various types of water through various types of water applicators by a distribution system applicators by a distribution system located on the soil surface, beneath the located on the soil surface, beneath the surface, or suspended above the surface, or suspended above the groundground

• Water is applied as drops, tiny streams, Water is applied as drops, tiny streams, or spray, through emitters, sprayers, or or spray, through emitters, sprayers, or porous tubingporous tubing

Water Application Water Application CharacteristicsCharacteristics

• Low ratesLow rates• Over long periods of timeOver long periods of time• At frequent intervalsAt frequent intervals• Near or directly into the root zoneNear or directly into the root zone• At low pressureAt low pressure• Usually maintain relatively high water Usually maintain relatively high water

contentcontent• Used on higher value Used on higher value

agricultural/horticultural crops and in agricultural/horticultural crops and in landscapes and nurserieslandscapes and nurseries

Schematic of a Typical Microirrigation SystemSchematic of a Typical Microirrigation System

AdvantagesAdvantages

• High application efficiencyHigh application efficiency• High yield/qualityHigh yield/quality• Decreased energy requirementsDecreased energy requirements• Reduced salinity hazardReduced salinity hazard• Adaptable for chemigationAdaptable for chemigation• Reduced weed growth and disease Reduced weed growth and disease

problemsproblems• Can be highly automatedCan be highly automated

DisadvantagesDisadvantages

• High initial costHigh initial cost• Maintenance requirements Maintenance requirements

(emitter clogging, etc.)(emitter clogging, etc.)• Restricted plant root developmentRestricted plant root development• Salt accumulation near plants Salt accumulation near plants

(along the edges of the wetted (along the edges of the wetted zone) zone) 

Salt Movement Under Irrigation with Saline WaterSalt Movement Under Irrigation with Saline Water

Salt accumulation leached Salt accumulation leached downward by successive water downward by successive water applicationsapplications

Salt accumulation leached Salt accumulation leached radially outward from drip radially outward from drip tubingtubing

Subsurface DripSubsurface Drip Sprinkler/FloodSprinkler/Flood

Types of SystemsTypes of Systems

•  Surface trickle (drip)Surface trickle (drip)– Water applied through small emitter Water applied through small emitter

openings to the soil surface (normally openings to the soil surface (normally less than 3 gal/hr per emitter)less than 3 gal/hr per emitter)

– Most prevalent type of microirrigationMost prevalent type of microirrigation– Can inspect, check wetting patterns, Can inspect, check wetting patterns,

and measure emitter dischargesand measure emitter discharges

Point Source Emitters in a New OrchardPoint Source Emitters in a New Orchard

Types of Systems Types of Systems ContdContd…

• SpraySpray– Water applied (spray, jet, fog, mist) to the Water applied (spray, jet, fog, mist) to the

soil surface at low pressure (normally less soil surface at low pressure (normally less than about 1 gal/min per spray applicator)than about 1 gal/min per spray applicator)

– Aerial distribution of water as opposed to Aerial distribution of water as opposed to soil distributionsoil distribution

– Reduced filtration and maintenance Reduced filtration and maintenance requirements because of higher flow raterequirements because of higher flow rate

Types of Systems Types of Systems Contd…Contd…

• BubblerBubbler– Water applied as a small stream to flood the Water applied as a small stream to flood the

soil surface in localized areas (normally less soil surface in localized areas (normally less than about 1 gal/min per discharge point)than about 1 gal/min per discharge point)

– Application rate usually greater than the Application rate usually greater than the soil's infiltration rate (because of small soil's infiltration rate (because of small wetted diameter)wetted diameter)

– Minimal filtration and maintenance Minimal filtration and maintenance requirementsrequirements

Types of Systems Types of Systems ContdContd…

• Subsurface trickleSubsurface trickle– Water applied through small emitter Water applied through small emitter

openings below the soil surfaceopenings below the soil surface– Basically a surface system that's been Basically a surface system that's been

buried (few inches to a couple feet)buried (few inches to a couple feet)– Permanent installation that is "out of Permanent installation that is "out of

the way"the way"

30 in30 in

60 in60 in

Typical Subsurface Drip Tubing Installation for Row CropsTypical Subsurface Drip Tubing Installation for Row Crops

12 – 14 in12 – 14 in

Non Wheel- Non Wheel- Track RowTrack Row

Wetting PatternWetting Pattern

Drip TubingDrip Tubing

60-inch dripline spacing is satisfactory on silt loam & clay loam soils60-inch dripline spacing is satisfactory on silt loam & clay loam soils

System ComponentsSystem Components

•  PumpPump•   Control headControl head

– FiltersFilters– Chemical injection equipment (tanks, Chemical injection equipment (tanks,

injectors, backflow prevention, etc.)injectors, backflow prevention, etc.)– Flow measurement devicesFlow measurement devices– ValvesValves– ControllersControllers– Pressure regulatorsPressure regulators

System Components, System Components, ContdContd…

• Mainlines and Submains (manifolds)Mainlines and Submains (manifolds)– Often buried and nearly always plastic Often buried and nearly always plastic

(PVC)(PVC)

• LateralsLaterals– Plastic (PE)Plastic (PE)– Supply water to emitters (sometimes Supply water to emitters (sometimes

"emitters" are part of the lateral itself)"emitters" are part of the lateral itself)

Applicator HydraulicsApplicator Hydraulics

• GeneralGeneral– Need pressure in pipelines to distribute Need pressure in pipelines to distribute

water through the system, but the water through the system, but the applicator needs to dissipate that applicator needs to dissipate that pressurepressure

– qqee = emitter discharge = emitter discharge

– K = emitter discharge coefficientK = emitter discharge coefficient– H = pressure head at the emitterH = pressure head at the emitter– X = emitter discharge exponent X = emitter discharge exponent

(varies with emitter (varies with emitter type)type)

xKHeq

Characteristics of Various Types of EmittersCharacteristics of Various Types of Emitters

Emitter HydraulicsEmitter Hydraulics  

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 1.00Porous Pipe - 0.112 1.00 2.072.07 3.13.1 4.144.14

Tortuous Path 0.112 0.65Tortuous Path 0.112 0.65 0.750.75 0.970.97 1.171.17

Vortex/Orifice 0.112 0.42Vortex/Orifice 0.112 0.42 0.380.38 0.450.45 0.510.51

Compensating 0.112 0.20Compensating 0.112 0.20 0.200.20 0.220.22 0.230.23

Estimating Emitter Exponent & CoefficientEstimating Emitter Exponent & Coefficient

Requires discharges qRequires discharges qe1e1, q, qe2e2 at two pressures h at two pressures h11, h, h22

• Emitter ExponentEmitter Exponent

• Emitter CoefficientEmitter Coefficient

oror

)/log(

)/log(

21

21

hh

qqx

ee

xh

qK

1

1

xh

qK

2

2

• Emitters (Point Source)Emitters (Point Source)– Long-pathLong-path– OrificeOrifice– VortexVortex– Pressure compensating (x < 0.5)Pressure compensating (x < 0.5)– FlushingFlushing

• Line-source tubingLine-source tubing– Porous-wall tubing (pores of capillary size that Porous-wall tubing (pores of capillary size that

ooze water)ooze water)– Single-chamber tubing (orifices in the tubing or Single-chamber tubing (orifices in the tubing or

pre-inserted emitters)pre-inserted emitters)– Double-chamber tubing (main and auxiliary Double-chamber tubing (main and auxiliary

passages)passages)

Applicator Hydraulics Applicator Hydraulics ContdContd…

– SprayersSprayers• Foggers, spitters, misters, etcFoggers, spitters, misters, etc• Relatively uniform application over the wetted Relatively uniform application over the wetted

areaarea

• Lateral hydraulicsLateral hydraulics– Very much like sprinkler hydraulics, but on Very much like sprinkler hydraulics, but on

a smaller scalea smaller scale– Since there is usually a large number of Since there is usually a large number of

emitters, multiple outlet factor (F) emitters, multiple outlet factor (F) 0.35 0.35

Other Design and Management Other Design and Management IssuesIssues

•  CloggingClogging– Physical (mineral particles)Physical (mineral particles)– Chemical (precipitation)Chemical (precipitation)– Biological (slimes, algae, etc.)Biological (slimes, algae, etc.)

• FiltrationFiltration– Settling basinsSettling basins– Sand separators (centrifugal or Sand separators (centrifugal or

cyclone separators)cyclone separators)– Media (sand) filtersMedia (sand) filters– Screen filtersScreen filters

There are many different types There are many different types of filtration systems. of filtration systems. There are many different types There are many different types of filtration systems. of filtration systems.

                         

The type is dictated by The type is dictated by the water source and the water source and also by emitter size. also by emitter size.

The type is dictated by The type is dictated by the water source and the water source and also by emitter size. also by emitter size.

Filtration Requirements for Drip EmittersFiltration Requirements for Drip Emitters

Filter openings should be Filter openings should be 1/71/7thth – 1/10 – 1/10thth the size of the size of the emitter orificethe emitter orifice

0.020-inch orifice0.020-inch orifice

Plugging Potential of Irrigation Water for Microirrigation

• Chemical treatmentChemical treatment– Acid: prevent calcium precipitationAcid: prevent calcium precipitation– ChlorineChlorine

• control biological activity: algae and bacterial slimecontrol biological activity: algae and bacterial slime• deliberately precipitate irondeliberately precipitate iron

•   FlushingFlushing– after installation or repairs, and as part of after installation or repairs, and as part of

routine maintenanceroutine maintenance– valves or other openings at the end of all pipes, valves or other openings at the end of all pipes,

including lateralsincluding laterals

• Application uniformityApplication uniformity– manufacturing variationmanufacturing variation– pressure variations in the mainlines and pressure variations in the mainlines and

lateralslaterals– pressure-discharge relationships of the pressure-discharge relationships of the

applicatorsapplicators

Subsurface Drip Irrigation Subsurface Drip Irrigation AdvantagesAdvantages

• High water application efficiency

• Uniform water application

• Lower pressure & power requirements

• Adaptable to any field shape

• No dry corners (vs. center pivot)

• Adaptable to automation

Subsurface Drip Irrigation Subsurface Drip Irrigation DisadvantagesDisadvantages

• High initial cost

• Water filtration required

• Complex maintenance requirements– Flushing, Chlorination, Acid injection

• Susceptible to gopher damage

• Salt leaching limitations

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)

Subsurface DripSubsurface Drip Center PivotCenter Pivot

Area IrrigatedArea Irrigated 160 acres160 acres 125 acres125 acres

Initial CostInitial Cost $800-1000/acre$800-1000/acre $280-360/acre$280-360/acre

Irrigation EfficiencyIrrigation Efficiency 90-95%90-95% 70-85%70-85%

Water RequirementWater Requirement 5.0-5.3 gpm/acre5.0-5.3 gpm/acre 5.5-6.8 gpm/acre5.5-6.8 gpm/acre

Operating PressureOperating Pressure 10-20 psi10-20 psi 25-35 psi25-35 psi

Energy RequirementEnergy Requirement(250-ft lift, ¼ mile supply line)(250-ft lift, ¼ mile supply line)

36 hp-hr/ac-in36 hp-hr/ac-in 48 hp-hr/ac-in48 hp-hr/ac-in

Gopher Damage on Subsurface Drip TubingGopher Damage on Subsurface Drip Tubing

Schematic of Subsurface Drip Irrigation (SDI) SystemSchematic of Subsurface Drip Irrigation (SDI) System

Pump Pump StationStation

BackflowBackflowPreventionPrevention

DeviceDevice

FlowmeterFlowmeter

Chemical Chemical Injection Injection SystemSystem

Air & VacuumAir & VacuumRelease ValveRelease Valve

X X

Pressure GagePressure Gage

X X

Flush Valve Flush Valve

XX

Dripline Dripline LateralsLaterals

ZonesZones1 and 1 and

22

SubmainSubmain

FlushlineFlushline

Filtration Filtration SystemSystem

x

X Zone Valve Zone Valve

Diagram courtesy of Kansas State UniversityDiagram courtesy of Kansas State University

Turbulent flow PVC emitter welded inside tubingTurbulent flow PVC emitter welded inside tubing

Netafim TyphoonNetafim Typhoon®® Drip Irrigation Tubing Drip Irrigation Tubing(Clear Demo Tubing)(Clear Demo Tubing)

16-mm diameter, seamless, 13-mil thick extruded PE tubing16-mm diameter, seamless, 13-mil thick extruded PE tubing

Emitter outletEmitter outlet

Netafim TyphoonNetafim Typhoon®® Drip Irrigation Tubing Drip Irrigation Tubing

Flap over emitter outlet:Flap over emitter outlet:- prevents root intrusion- prevents root intrusion- prevents blockage by mineral scale- prevents blockage by mineral scale

30 in30 in

60 in60 in

Typical Drip Tubing Installation for Row CropsTypical Drip Tubing Installation for Row Crops

12 – 14 in12 – 14 in

Non Wheel- Non Wheel- Track RowTrack Row

Wetting PatternWetting Pattern

Drip TubingDrip Tubing

60-inch dripline spacing is satisfactory on silt loam & clay loam soils60-inch dripline spacing is satisfactory on silt loam & clay loam soils

Wetting Pattern of a Subsurface Drip LateralWetting Pattern of a Subsurface Drip Lateral

Photo Courtesy of Kansas State UniversityPhoto Courtesy of Kansas State University

Wider dripline spacings may not work.Wider dripline spacings may not work.Wider dripline spacings may not work.Wider dripline spacings may not work.

Photo Courtesy of Kansas State UniversityPhoto Courtesy of Kansas State University

SDI System MaintenanceSDI System Maintenance

• Lateral flushing scheduleLateral flushing schedule (sediment)(sediment)

• Chlorine injection Chlorine injection scheduleschedule(biological growths)(biological growths)

• Acid injection scheduleAcid injection schedule(chemical precipitates & scaling)(chemical precipitates & scaling)

Salt Movement Under Irrigation with Saline WaterSalt Movement Under Irrigation with Saline Water

Salt accumulation leached Salt accumulation leached downward by successive water downward by successive water applicationsapplications

Salt accumulation leached Salt accumulation leached radially outward from drip radially outward from drip tubingtubing

Subsurface DripSubsurface Drip Sprinkler/FloodSprinkler/Flood

Small research plots during supply line installationSmall research plots during supply line installation

Plowing in drip tubingPlowing in drip tubing

Trenching across the drip tubing ends for PVC manifold installationTrenching across the drip tubing ends for PVC manifold installation

Drip tubing end after being sheared by the trencher

Components for Drip Lateral-Submain ConnectionComponents for Drip Lateral-Submain Connection

21/32” Hole in Submain21/32” Hole in Submain

Neoprene GrommetNeoprene Grommet

Polyethylene Polyethylene Barb AdapterBarb Adapter

5/8” Polyethylene 5/8” Polyethylene Supply Tube Supply Tube (Usually 2-3 ft long)(Usually 2-3 ft long)

Stainless Steel Wire Twist TieStainless Steel Wire Twist Tie

5/8” Drip Irrigation Tubing5/8” Drip Irrigation Tubing

Typical Drip Tubing Connection to SubmainTypical Drip Tubing Connection to Submain(1 ½ -inch Submains and Larger)(1 ½ -inch Submains and Larger)

Supply Submain or Flushing ManifoldSupply Submain or Flushing Manifold

Neoprene Grommet Inserted Neoprene Grommet Inserted in 21/32” hole in manifoldin 21/32” hole in manifold

Polyethylene Barb Adapter Polyethylene Barb Adapter Inserted in GrommetInserted in Grommet

5/8” Polyethylene 5/8” Polyethylene Supply Tubing Supply Tubing 5/8” Drip 5/8” Drip

Irrigation TubingIrrigation Tubing

Stainless Steel Stainless Steel Wire Twist TieWire Twist Tie

Identical connection on distal end for flushing manifold connectionIdentical connection on distal end for flushing manifold connection

Flush Risers on Distal End of Research PlotsFlush Risers on Distal End of Research Plots

Ball Valve for Manual Ball Valve for Manual Flushing of Drip LateralsFlushing of Drip Laterals

Air Vent to Release Air Vent to Release Trapped Air from LateralsTrapped Air from Laterals

SDI Water Application RatesSDI Water Application Rates(inches/hour)(inches/hour)

(60-inch tubing spacing)(60-inch tubing spacing)

12 inches12 inches 18 inches18 inches 24 inches24 inches

0.16 gph0.16 gph 0.0430.043 0.0340.034 0.0260.026

0.21 gph0.21 gph 0.0560.056 0.0450.045 0.0340.034

0.33 gph0.33 gph 0.0880.088 0.0710.071 0.0530.053

0.53 gph0.53 gph 0.1420.142 0.1130.113 0.0850.085

Emitter SpacingEmitter Spacing

Emitter DischargeEmitter Discharge