Tools for Practical Irrigation Scheduling

1. Tools for Practical Irrigation Scheduling R. Troy Peters, Ph.D., P.E. Washington State University Irrigated Agriculture Research and Extension Center Prosser, WA

2. Irrigation SchedulingEverybody Wins! • Better Yields. • Better Crop Quality. • Use less water. • Save power • Water available for alternative uses. • Less leaching of water, nutrients, pesticides. • Improved environmental quality.

3. Soil Water Balance Water In = Water Out + ΔStorage

4. Soil Water Balance

5. Soil is a Water & Nutrient Reservoir Irrigation or Precipitation = Water In Deep Percolation = Overflow Field Capacity (full) Soil Water Content (soil moisture measurement) Water Holding Capacity (AW * Rz) = Size of Reservoir ET = Water Out Wilting Point (empty)

6. Field Capacity (FC): Maximum amount of water that a soil can hold indefinitely against gravity (% of volume) • Permanent Wilting Point (PWP): The amount of water remaining in the soil after plants can no longer pull water from the soil (wilt & die) • Available Water (AW) = FC - PWP

7. Soil Texture and Available Water

8. How Big is Your Reservoir? How much water can it hold? When will it be empty? Deep Silt Deep Sand ET ET Shallow Silt Shallow Sand ET ET

9. Starting from full, after a few days of water use. Sand Silt ET ET

10. Production Reduction Function FC MAD PWP

11. Alfalfa Apples Asparagus Corn Hop Mint Potato Winter Wheat 65 50 - 65 50 65 65 35 20 - 35 50 - 65 Crop MAD (%)

12. Estimate ET ETc = ETr x Kc ETc = crop evapotranspiration ETr = evapotranspiration rate of a reference crop (alfalfa). Function of the weather. Kc = crop coefficient. Function of the plants.

13. 0.40 0.35 0.30 0.25 0.20 0.15 ET (inches/day) 0.10 0.05 0.00 4/10 5/10 6/09 7/09 8/08 9/07 10/07 Date ET and Weather

15. Variation in Crop Water Use from growing season to growing season Average Crop Water Use Crop Water Use Germination and Emergence Vegetative Growth Reproduction (seed set) Maturity and Senascence Growing Season

17. Good Irrigation Management

18. Poor Irrigation Management

19. Simple soil water balance based on ET. • Designed for use on a smart phone, but usable on any desktop web browser. • Designed for usability #1. • Quick & easy to set up. • Automatically pulls ET data from selected weather stations. • Can run on any weather network who’s data can be automatically accessed.

20. Don’t ask farmers questions they don’t know or have to look up. • Make is simple enough that they can play with the inputs. • Tools they will use = Simple and Robust.

21. Android App is functional. • iPhone App will be ready by Spring.

24. Current Use

37. Specific help link on every screen

38. AppleiPhoneiPadiPodweather.wsu.edu/ismin SafariThen…

39. Then

40. Looks and behaves like an app! runs in Safari

41. Android

42. AndroidGoogle Play Store

45. Additional Features • Copy settings from an existing field for quick setup or reset for new year. • One-week ETc forecast • NWS max & min forecast & Hargreaves eqtn. • Can use hrs of irrigation run time instead of inches of applied water. • Integrated calculators to help calc app. rate. • Correction for dry, un-irrigated inter-rows (adjustment to water holding capacity)

46. Additional Features • Option for notifications via email or text. • Download all data to a .csv from full-page. • Use reporting. • Shows what users do and when. • Can set up different crop defaults for different states, or climatological regions. • i.e. can make it state-specific. • Crop Kc, growth dates, MAD, • Free and Open source. (PHP, MySQL)

47. Feedback • Growers are generally pleased with it and are using it on their own. • Setting up and customizing for own field is important. • Need to keep up with entering irrigation events (record keeping).

48. Questions? http://weather.wsu.edu/ism R. Troy Peters, Ph.D., P.E.