Performance of a Variable Rate Center Pivot System

US farmers have access to equipment for variable-rate application of most inputs, but some potential benefits of precision agriculture may be masked by uniform application of irrigation water. A system developed at the University of Georgia for variable-rate (VR) water application was installed on a 400-m long center pivot system at the Judd Hill Plantation in northeast Arkansas. The objective of this research is to monitor the system to determine the potential for water and energy savings. A replicated large-plot study was initiated in 2006 based on soil mapping units. Application rates were 13, 19, and 23 mm. No significant cotton yield differences were observed in 2006, probably due to rainfall at the site in July and August. Instrumentation installed in 2007 showed a slightly lower water flow rate and increased water pressure when the end gun was shut off, but the fuel flow rate did not change. The water flow rate decreased during the study period and an additional sensor will be added to test for changes in the water table depth. Future studies are planned to repeat the large-plot study of 2006, monitor the system under a wider range of operating conditions, and investigate possible variable rate nitrogen application through the irrigation system.