2. IRRIGATION GUIDANCE FOR PLANNERS Rick Schlegel Irrigation Engineer USDA - NRCS

3. FIRST STEP - DO AN IRRIGATION SYSTEM INVENTORY  System capacity or flow available  Conveyance system & condition  Irrigation system types  Crops to be irrigated  Predominate soil types being irrigated  Irrigation water management being practiced by producer

4. AFTER COMPLETING INVENTORY  After the inventory is done, decide if the existing system is adequate or if the irrigator needs to:  Install a new irrigation system  Install flowmeters or chemigation valves  Install a new pipeline or delivery system  Change his cropping system to be more efficient  Manage or schedule irrigation applications  Decommission inadequate wells

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

6. SYSTEM CAPACITY  Needs to be large enough to meet crop water needs in a timely manner  RULE OF THUMB FOR PLANNERS:  High water use crops such as corn or peanuts - 7.0 gpm/acre needed  Medium water use crops such as cotton, milo, soybeans – 5.0 gpm/acre needed  Minimum to meet standard – 3.0 gpm/acre

8. PUMP CURVES

10. Conveyance System  Generally use underground PVC  Replace leaky or undersized lines  RULE OF THUMB FOR PLANNERS: Below 400 gpm – 6” PVC 400 – 750 gpm – 8” PVC 750 – 1200 gpm – 10” PVC 1200 – 1700 gpm – 12” PVC 1200 – 1700 gpm – 12” PVC  Plan High Pressure Line when delivery system is long length or large elevation increases are encountered

17. COMMON IRRIGATION SYSTEMS UNDER EQIP  LEPA – Low Energy Precision Application  LESA – Low Elevation Spray Application  LPIC – Low Pressure In Canopy  MESA – Mid Elevation Spray Application  Drip System or Microirrigation

18. LEPA SYSTEM

21. LESA SYSTEM

23. LPIC SYSTEM

25. MESA MESA SYSTEM

27. CROPS AND SOILS  Determine crops to be irrigated  Determine predominate soils to be irrigated  Use Oklahoma Irrigation Guide to gather information for IWM plan  Teach producer how to do Irrigation Scheduling

28. UNDERSTANDING SOIL – WATER – PLANT RELATIONSHIPS

29. TYPICAL CROP ROOT ZONE

30. RAINFALLRAINFALL IRRIGATIONIRRIGATION

31. EVAPORATIONEVAPORATION TRANSPIRATIONTRANSPIRATION ET EVAPOTRANSPIRATION ET EVAPOTRANSPIRATION DEEP PERCOLATION

32. AVAILABLE WATER CAPACITY (AWC)  THE ROOT ZONE CAN ONLY HOLD SO MUCH WATER ( FIELD CAPACITY ). THE REST IS LOST TO DEEP PERCOLATION.  “AWC” IS THE AMOUNT OF WATER HELD IN THE ROOT ZONE OF THE CROP THAT IS AVAILABLE TO THE CROP.

33. AWCAWC AVAILABLE WATER CAPACITY

34. SANDY CLAY LOAM, LOAM, & SILT LOAM 1.8 IN/FOOT SANDY CLAY LOAM, LOAM, & SILT LOAM 1.8 IN/FOOT SANDY LOAM & FINE SANDY LOAM 1.5 IN/FOOT SANDY LOAM & FINE SANDY LOAM 1.5 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

35. MANAGING THE AVAILABLE WATER Using Management Allowable Depletion MAD

36. AWCAWC MAD WATER BALANCE MADMAD STINGYSTINGY

37. TWO METHODS PLANNED  1. Manage the available moisture at 50% AWC  2. Manage the available moisture to let it drop to the level of a typical producer irrigation plus leaving a one to two inch depletion for rainfall. (1.5” + 1.0” = 2.5”)

38. “MAD” EXAMPLES AT 50%  CROP WITH FOUR FOOT ROOT ZONE:  CLAY, CLAY LOAM, OR SILTY CLAY LOAM AWC = 8.0” MAD WB= 4.0”  SANDY CLAY LOAM, LOAM, OR SILT LOAM AWC = 7.2” MAD WB= 3.6”  SANDY LOAM OR FINE SANDY LOAM AWC = 6.0” MAD WB= 3.0”  FINE SAND OR LOAMY FINE SAND AWC = 3.6” MAD WB= 1.8”

39. AVAILABLE WATER CAPACITY CAN ALSO BE LIMITED BY:

40. PLOW PAN AWC

41. DEVELOPING AN IRRIGATION WATER MANAGEMENT PLAN

47. SCHEDULING IRRIGATION USING EVAPOTRANSPIRATION METHODS

48. Evapotranspiration Methods  Using the Atmometer  Using the Agweather Site on the Mesonet

51. EVAPOTRANSPIRATION USING THE OKLAHOMA MESONET

60. USING MESONET “ET” DATA

61. USING EXCEL SPREADSHEET

64. EQIP Incentive Payment ($10/acre)  Eight basic requirements:  1. Irrigation system meets standards  2. IWM plan is followed  3. Report flow twice during season  4. Install two rain guages and record rain  5. Determine daily ET to use in scheduler  6. Spot check soil moisture monthly  7. Record irrigation amounts and durations  8. Keep scheduler & records & submit to NRCS  9. USE SCHEDULER TO MAKE DECISIONS