Submitted to: Annual Southern Conservation Tillage Conference for Sustainable Agriculture
Publication Type: Proceedings
Publication Acceptance Date: May 15, 2006
Publication Date: June 15, 2006
Citation: Evett, S.R., Peters, R.T., Howell, T.A. 2006. Controlling water use efficiency with irrigation automation: Cases from drip and center pivot irrigation of corn and soybean. In: Proceedings of the 28th Annual Southern Conservation Systems Conference, June 26-28, 2006, Amarillo, Texas. p. 57. Interpretive Summary: Automation of irrigation system water applications can reduce manager time and effort considerably while maintaining yields and allowing control of water use efficiency of cropping systems. By preventing over irrigation, automated systems can reduce fertilizer and water losses to deep percolation and improve yields. We tested an automation system that measures crop leaf temperature and applies irrigations when the crop is warmer than an optimum temperature for that crop for longer than a set time that is regionally specific. We determined the time set points for corn and soybeans in our region. Tests conducted using both drip irrigation and center pivot irrigation systems showed that either type of system could be successfully automated, and that yields of corn and soybean were as large as those obtained when very time consuming and expensive manual measurements of soil water content were used to schedule irrigation. These soil water content measurements are seldom used by farmers, so the automated system will outperform most scheduling methods currently used by farmers. For corn in particular, the automated system provided larger yields under droughty conditions because the response to water stress was immediate during critical plant growth stages, such as silking and pollination. Also for corn, the automated system showed that the ratio of yield to water used, also know as water use efficiency, could be controlled by choosing temperature and time set points.
Technical Abstract: A center pivot was completely automated using the temperature-time-threshold (TTT) method of irrigation scheduling. Methods are described that were used to automatically collect and analyze canopy temperature data and control the moving irrigation system based on the data analysis. Automatic irrigation treatments were compared with manually scheduled irrigation treatments under the same center pivot during the growing seasons of 2004 and 2005. Manual irrigations were scheduled on a weekly basis using the neutron probe to determine the profile water content and the amount of water needed to replenish the profile to field capacity. In both years there was no significant difference between manual and automatic treatments in soybean water use efficiency or irrigation water use efficiency. Using drip irrigation in an earlier study, the automated irrigation method resulted in soybean and corn yields and water use efficiencies that were also not significantly different from those obtained with manual scheduling. However with corn, the automated system responded to crop stress better, prevented yield decline in a droughty year, and showed that water use efficiency could be controlled by varying the system parameters. The automatic irrigation system has the potential to simplify management while maintaining the yields of intensely managed irrigation.