|Peters, R - WASHINGTON STATE UNIV.|
Submitted to: Proceedings of the USCID Wetlands Seminar
Publication Type: Proceedings
Publication Acceptance Date: September 1, 2006
Publication Date: October 1, 2006
Citation: Peters, R.T., Evett, S.R. 2006. A fully automated center pivot using crop canopy temperature: Preliminary results. Ground Water and Surface Water Under Stress: Competition, Interaction, Solutions. A USCID Water Management Conference, October 25-28, 2006, Boise, Idaho. p 139-148. Interpretive Summary: Center pivot irrigation systems are used on more than 70% of the irrigated land in the U.S. Southern Great Plains. These irrigated lands produce more than 60% of feed grains on only 20% of the farmed lands in the region and are crucial to supporting the region’s economically key cattle feeding industry. However, declining water tables and well yields are reducing farmers’ ability to irrigate, and more efficient irrigation management is needed. The center pivot is itself an efficient method of irrigation application; but the scheduling of irrigations is often done by eye and intuition, leading to common over-irrigation of crops. This results in water wastage and reduced yields as fertilizer is lost to deep percolation of the applied water. The Soil and Water Management Research Unit of the USDA-ARS at Bushland, Texas has developed a method and system of sensors, electronic control hardware and software that completely automates a center pivot. Results show that the automated system applies irrigations when needed by the crop and produces yields and water use efficiencies that are as good as the best scientific irrigation scheduling method. The latter method involves weekly measures of soil water content throughout a field and is not used by farmers because it is labor intensive and expensive. The automated system senses crop leaf temperatures and identifies when the crop is water stressed, then starts the pump and center pivot automatically. The system reduces farmers’ management time and labor and is fully compatible with the control panels on current center pivot irrigation systems.
Technical Abstract: It has been shown that the temperature-time threshold (TTT) method of automatic irrigation scheduling is a viable alternative to traditional soil water based irrigation scheduling in the Southern High Plains. This method was used to fully automate a center pivot in the panhandle of Texas. An array of 16 infrared thermocouple thermometers (IRTCs) were mounted on the pivot and connected to a datalogger also mounted on the pivot. A separate array of IRTCs were located in stationary position in the field and connected to a separate datalogger. Two different spread spectrum (900 MHz) radios were connected to a desktop computer located nearby that queried both dataloggers, got pivot status information, and sent commands to the center pivot control panel. Using scheduled data collection intervals, this computer was able to collect the data, analyze it, determine the need for an irrigation event, and issue control commands to completely automate the center pivot. The field under the pivot was divided into pie slices with every other pie slice an automatic treatment. The pie slices in between served as the control and these were scheduled manually to refill the soil water content to field capacity on a weekly basis using neutron probe soil moisture measurements. The preliminary results from this experiment are presented and the statistics showing the differences between the two methods are given.