Submitted to: International Irrigation Show
Publication Type: Proceedings
Publication Acceptance Date: November 4, 2001
Publication Date: November 4, 2001
Interpretive Summary: Irrigation of crops should be done at times and with quantities of water that avoid waste of water and that maximize the use of rainfall while maintaining high yields. This is difficult to do with current manual irrigation scheduling methods. An automatic irrigation scheduling and control system was investigated for drip irrigation of corn and soybean. The system relies on measurements of crop leaf temperature. It assessed crop water stress levels by comparing the leaf temperature to a threshold temperature that was determined for a well-watered, unstressed crop. The automatic system was compared against a manual method that used soil water measurements to assess the amount of water used by the crop each week, so that the next irrigation could apply that amount of water to replenish the soil water reservoir. Over two years with quite different rainfall amounts, corn yield, total water use and water use efficiency (WUE, the amount of yield per inch of water used) were stable for the automatic irrigation treatments. But, corn water use and WUE varied widely over the two years of corn production for the manual treatments. The automatic system was able to respond to low stress levels resulting from good rainfall, and thus, delivered larger irrigation WUE values when rainfall was more plentiful. For soybean, yields and WUE were not more stable for all automatic treatments. It appears that the automatic irrigation system will allow a choice between larger yields or larger water use efficiencies to be achieved for corn, but not for soybean. However for both crops, the automatic system delivered yields as large or larger than those obtained with the manual system in all years, with less management time and effort.