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Automatic Irrigation Scheduling of Grain Sorghum Using an Integrated CWSI

Automatic Irrigation Scheduling of Grain Sorghum Using an Integrated CWSI. S.A. O’Shaughnessy, S.R. Evett, P.D. Colaizzi, and T.A. Howell USDA-ARS Bushland, TX USA 5 th Decennial Irrigation Association Conference December 5, 2010. Introduction.

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Automatic Irrigation Scheduling of Grain Sorghum Using an Integrated CWSI

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  1. Automatic Irrigation Scheduling of Grain Sorghum Using an Integrated CWSI S.A. O’Shaughnessy, S.R. Evett, P.D. Colaizzi, and T.A. Howell USDA-ARS Bushland, TX USA 5th Decennial Irrigation Association Conference December 5, 2010

  2. Introduction • Irrigation scheduling using remote ground-based and in-situ sensors will be a key element to irrigation automation. • As of recent, our interest has been in the theoretical CWSI, a stress index developed by: • Jackson et al., 1981 • and utilized for irrigation timing for a variety of different crops to include corn, wheat, alfalfa, and sorghum; • however its performance has been marginal.

  3. Objectives • Investigate the usefulness of the CWSI as a trigger for automatic irrigation scheduling over: • a relatively long period of time • and frequently over the growing season. • Analyze sorghum yield response to automated vs. manual methods of irrigation; • Examine water use efficiency at deficit irrigation levels.

  4. Materials Field Layout for 3 span center pivot system

  5. Materials Cont’d: • Sensors • Infrared thermometers on pivot lateral and within cropped field • Meteorological instruments- RH, air temperature, wind speed, and short wave radiation pyranometer anemometer infrared thermometers

  6. Center pivot as a platform for sensors

  7. Methods • Crop was planted in concentric rows, spaced 0.76 m apart • LEPA irrigation in every other furrow using drag socks • Rows were furrow-diked • Manual pie sections were irrigated over odd DOY to replenish soil water depletion (based on weekly neutron probe measurements) in the top 1.5 m • Automatic pie sections were irrigated on even DOY, if an irrigation signal was received

  8. Methods cont’d: • An irrigation signal was scheduled for the automatic treatments if: • CWSI ≥ 0.45 for a cumulative time threshold ≥ 420 min in a 24 hour period. • Irrigation Treatments were 80%, 55%, 30%, and 0% of twice the daily peak water use

  9. Methods cont’d: • Calculation of CWSI

  10. Calculation CWSI cont’d: Theoretical approach- (Jackson, et al., 1981) ra = ln [(z-d)/zo]/k2/U, Upper Limit: Lower Limit:

  11. Efficiency Calculations: Water use efficiency: Irrigation water use efficiency (IWUE, kg m-3): where Ygi is the economic yield (g m-2) from irrigation treatment level i, Ygd is the I0% yield (g m-2), and IRRi is the irrigation water applied (mm) (Howell, 2001).

  12. Results

  13. Average difference in early-season soil water levels (Manual -Automatic Treatment Plots)

  14. Climatic conditions for the 2009 growing season Cumulative rainfall = 240 mm Boot Flowering Grain filling

  15. Cumulative irrigations for the manual and automatic control methods plotted against time and key growth stages.

  16. Grain Yield Response d, f f d e b p=.73 c p=.05 p=.03 a a p=.97

  17. Comparative Water Use Efficiency

  18. Irrigation water use efficiency per irrigation depth

  19. Preliminary Conclusions • Repeated field trials are necessary with the same crop; this algorithm was tested on a long season grain sorghum in 2010. • Applied irrigation amounts between the manual and automatic methods were not significantly different • Remote identification of the hard dough stage would be beneficial to automatically terminate irrigations. • Additional testing on different crops and in different regions is required to validate the efficacy of this stress index as an irrigation trigger.

  20. Acknowledgements • Funding from the • Ogallala Aquifer Program • National Sorghum Checkoff Program • The technicians at Bushland CPRL

  21. Thank you for your attention!

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