|Peters, R - WASHINGTON STATE UNIV|
Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 31, 2007
Publication Date: May 1, 2008
Citation: Peters, R.T., Evett, S.R. 2008. Automation of a center pivot using the temperature-time-threshold method of irriation scheduling. Journal of Irrigation and Drainage Engineering. 134(3):286-291. Interpretive Summary: Center pivot sprinkler irrigation systems are rapidly replacing surface irrigation that uses ditches and furrows in many parts of the USA. Center pivots apply water more efficiently and use less labor than surface irrigation. In the Southern High Plains, center pivots are now used on more than 70% of the irrigated area and are used in production of corn, cotton, sorghum, soybean, winter wheat and other crops. But, decisions on when to turn on and off center pivot systems are still difficult and many farmers do not use the tools that are available for making these decisions either because they do not understand the tools or because use of the tools is too time consuming for the number of fields and crops that they manage. Due to rising energy prices and water scarcity, it is becoming more important to make these decisions well. For example, saving 1 inch of irrigation water can translate into savings of millions of dollars in pumping costs across the Southern High Plains. A system that automatically measures crop leaf temperature and turns the center pivot on and off was developed and tested on soybean. The automatic system produced crop yields as large as did a very labor intensive irrigation decision method that involved measuring soil water content to a depth of several feet once a week at several locations. It also used water as efficiently as did the labor intensive method. The automatic irrigation system has the potential to simplify management and reduce labor costs while maintaining the yields of intensely managed irrigation.
Technical Abstract: A center pivot was completely automated using the temperature-time-threshold (TTT) method of irrigation scheduling. An array of infrared thermometers was mounted on the center pivot and these were used to remotely determine the crop leaf temperature as an indicator of crop water stress. We describe methods used to automatically collect and analyze the 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. The automatic irrigation system has the potential to simplify management while maintaining the yields of intensely managed irrigation.