IRRIGATION GUIDANCE IRRIGATION GUIDANCE FOR PLANNERSFOR PLANNERS

Rick Schlegel Rick Schlegel Irrigation Engineer Irrigation Engineer

USDA - NRCSUSDA - NRCS

FIRST STEP - DO AN IRRIGATION FIRST STEP - DO AN IRRIGATION SYSTEM INVENTORYSYSTEM INVENTORY

System capacity or flow availableSystem capacity or flow available Conveyance system & conditionConveyance system & condition Irrigation system typesIrrigation system types Crops to be irrigatedCrops to be irrigated Predominate soil types being irrigatedPredominate soil types being irrigated Irrigation water management being Irrigation water management being

practiced by producerpracticed by producer

AFTER COMPLETING AFTER COMPLETING INVENTORYINVENTORY

After the inventory is done, decide if the existing After the inventory is done, decide if the existing system is adequate or if the irrigator needs to:system is adequate or if the irrigator needs to:

Install a new irrigation systemInstall a new irrigation system Install flowmeters or chemigation valvesInstall flowmeters or chemigation valves Install a new pipeline or delivery systemInstall a new pipeline or delivery system Change his cropping system to be more efficientChange his cropping system to be more efficient Manage or schedule irrigation applicationsManage or schedule irrigation applications Decommission inadequate wellsDecommission inadequate wells

Let’s break down the inventory and Let’s break down the inventory and talk about each itemtalk about each item

SYSTEM CAPACITYSYSTEM CAPACITY

Needs to be large enough to meet crop Needs to be large enough to meet crop water needs in a timely mannerwater needs in a timely manner

RULE OF THUMB FOR PLANNERS:RULE OF THUMB FOR PLANNERS: High water use crops such as corn or High water use crops such as corn or

peanuts - 7.0 gpm/acre neededpeanuts - 7.0 gpm/acre needed Medium water use crops such as cotton, Medium water use crops such as cotton,

milo, soybeans – 5.0 gpm/acre neededmilo, soybeans – 5.0 gpm/acre needed Minimum to meet standard – 3.0 gpm/acreMinimum to meet standard – 3.0 gpm/acre

PUMP CURVESPUMP CURVES

Conveyance SystemConveyance System

Generally use underground PVCGenerally use underground PVC Replace leaky or undersized linesReplace leaky or undersized lines RULE OF THUMB FOR PLANNERS:RULE OF THUMB FOR PLANNERS:

Below 400 gpm – 6” PVCBelow 400 gpm – 6” PVC400 – 750 gpm – 8” PVC400 – 750 gpm – 8” PVC750 – 1200 gpm – 10” PVC750 – 1200 gpm – 10” PVC

1200 – 1700 gpm – 12” PVC1200 – 1700 gpm – 12” PVC Plan High Pressure Line when delivery Plan High Pressure Line when delivery

system is long length or large elevation system is long length or large elevation increases are encounteredincreases are encountered

COMMON IRRIGATION SYSTEMSCOMMON IRRIGATION SYSTEMSUNDER EQIPUNDER EQIP

LEPA – Low Energy Precision ApplicationLEPA – Low Energy Precision Application LESA – Low Elevation Spray ApplicationLESA – Low Elevation Spray Application LPIC – Low Pressure In CanopyLPIC – Low Pressure In Canopy MESA – Mid Elevation Spray ApplicationMESA – Mid Elevation Spray Application Drip System or MicroirrigationDrip System or Microirrigation

LEPA SYSTEMLEPA SYSTEM

LEPA SYSTEM

LESA SYSTEM

LPIC SYSTEM

MESAMESAMESA SYSTEM

CROPS AND SOILSCROPS AND SOILS

Determine crops to be irrigatedDetermine crops to be irrigated Determine predominate soils to be Determine predominate soils to be

irrigatedirrigated Use Oklahoma Irrigation Guide to gather Use Oklahoma Irrigation Guide to gather

information for IWM planinformation for IWM plan Teach producer how to do Irrigation Teach producer how to do Irrigation

SchedulingScheduling

UNDERSTANDING UNDERSTANDING SOIL – WATER – PLANT SOIL – WATER – PLANT

RELATIONSHIPSRELATIONSHIPS

TYPICAL CROP ROOT ZONE

RAINFALL

IRRIGATION

EVAPORATION

TRANSPIRATION

ETEVAPOTRANSPIRATION

ETEVAPOTRANSPIRATION

DEEP PERCOLATION

AVAILABLE WATER CAPACITY AVAILABLE WATER CAPACITY (AWC)(AWC)

THE ROOT ZONE CAN ONLY HOLD SO MUCH THE ROOT ZONE CAN ONLY HOLD SO MUCH WATER ( FIELD CAPACITY ). THE REST IS WATER ( FIELD CAPACITY ). THE REST IS LOST TO DEEP PERCOLATION.LOST TO DEEP PERCOLATION.

““AWC” IS THE AMOUNT OF WATER HELD IN AWC” IS THE AMOUNT OF WATER HELD IN THE ROOT ZONE OF THE CROP THAT IS THE ROOT ZONE OF THE CROP THAT IS AVAILABLE TO THE CROP.AVAILABLE TO THE CROP.

AWC

AVAILABLE WATER

CAPACITY

AVAILABLE WATER

CAPACITY

SANDY CLAY LOAM, LOAM, & SILT LOAM1.8 IN/FOOT

SANDY CLAY LOAM, LOAM, & SILT LOAM1.8 IN/FOOT

SANDY LOAM & FINE

SANDY LOAM1.5 IN/FOOT

SANDY LOAM & FINE

SANDY LOAM1.5 IN/FOOT

FINE SAND AND LOAMY FINE SAND

0.9 IN/FOOT

FINE SAND AND LOAMY FINE SAND

0.9 IN/FOOT

CLAY, CLAY LOAM &

SILTY CLAY LOAM

2.0 IN/FOOT

CLAY, CLAY LOAM &

SILTY CLAY LOAM

2.0 IN/FOOT

MANAGING THE MANAGING THE AVAILABLE WATERAVAILABLE WATER

Using Using

Management Allowable DepletionManagement Allowable Depletion

MAD MAD

AWC

MAD WATER

BALANCE

MAD WATER

BALANCE

MADSTINGY

TWO METHODS PLANNEDTWO METHODS PLANNED

1. Manage the available moisture at 1. Manage the available moisture at 50% AWC50% AWC

2. Manage the available moisture to let it 2. Manage the available moisture to let it drop to the level of a typical producer drop to the level of a typical producer irrigation plus leaving a one to two irrigation plus leaving a one to two

inch inch depletion for rainfall. (1.5” + 1.0” = depletion for rainfall. (1.5” + 1.0” = 2.5”)2.5”)

““MAD” EXAMPLES AT 50%MAD” EXAMPLES AT 50%

CROP WITH FOUR FOOT ROOT ZONE:CROP WITH FOUR FOOT ROOT ZONE: CLAY, CLAY LOAM, OR SILTY CLAY CLAY, CLAY LOAM, OR SILTY CLAY

LOAM AWC = 8.0” MAD WB= 4.0”LOAM AWC = 8.0” MAD WB= 4.0” SANDY CLAY LOAM, LOAM, OR SILT SANDY CLAY LOAM, LOAM, OR SILT

LOAM AWC = 7.2” MAD WB= 3.6”LOAM AWC = 7.2” MAD WB= 3.6” SANDY LOAM OR FINE SANDY LOAM SANDY LOAM OR FINE SANDY LOAM

AWC = 6.0” MAD WB= AWC = 6.0” MAD WB= 3.0”3.0”

FINE SAND OR LOAMY FINE SAND FINE SAND OR LOAMY FINE SAND AWC = 3.6” MAD WB= 1.8” AWC = 3.6” MAD WB= 1.8”

AVAILABLE WATER CAPACITY AVAILABLE WATER CAPACITY CAN ALSO BE LIMITED BY:CAN ALSO BE LIMITED BY:

PLOW PAN

AWC

DEVELOPING AN DEVELOPING AN IRRIGATION WATER IRRIGATION WATER MANAGEMENT PLANMANAGEMENT PLAN

SCHEDULING SCHEDULING IRRIGATIONIRRIGATION

USING EVAPOTRANSPIRATION USING EVAPOTRANSPIRATION METHODSMETHODS

Evapotranspiration MethodsEvapotranspiration Methods

Using the AtmometerUsing the Atmometer Using the Agweather Site on the MesonetUsing the Agweather Site on the Mesonet

EVAPOTRANSPIRATION USING EVAPOTRANSPIRATION USING THE OKLAHOMA MESONETTHE OKLAHOMA MESONET

USING MESONET “ET” DATAUSING MESONET “ET” DATA

USING EXCEL SPREADSHEETUSING EXCEL SPREADSHEET

EQIP Incentive Payment ($10/acre)EQIP Incentive Payment ($10/acre)

Eight basic requirements:Eight basic requirements: 1. Irrigation system meets standards1. Irrigation system meets standards 2. IWM plan is followed2. IWM plan is followed 3. Report flow twice during season3. Report flow twice during season 4. Install two rain guages and record rain4. Install two rain guages and record rain 5. Determine daily ET to use in scheduler5. Determine daily ET to use in scheduler 6. Spot check soil moisture monthly6. Spot check soil moisture monthly 7. Record irrigation amounts and durations7. Record irrigation amounts and durations 8. Keep scheduler & records & submit to NRCS8. Keep scheduler & records & submit to NRCS 9. USE SCHEDULER TO MAKE DECISIONS9. USE SCHEDULER TO MAKE DECISIONS