|Perry, C - UNIVERSITY OF GEORGIA|
|Stephenson, D - UNIVERSITY OF ARKANSAS|
|Tacker, P - UNIVERSITY OF ARKANSAS|
Submitted to: Asian Crop Science Conference
Publication Type: Proceedings
Publication Acceptance Date: June 30, 2007
Publication Date: August 2, 2007
Citation: Vories, E. D., C. Perry, D. Stephenson, and P. Tacker. 2007. Site-specific irrigation in the USA. Proc. 2nd Asian Conf. on Prec. Agric. (ACPA). Aug. 2-4, 2007, Pyeongtaek, Korea. [unpaginated CDROM]. Interpretive Summary: Farms in the USA are typically larger than in many parts of the world and the combination of large farms and a small labor force have led U.S. farmers to operate on a larger scale than their counterparts in many other countries. An example of large-scale irrigation equipment is the center pivot, and the objective of this research is to monitor a variable-rate system installed on a center pivot at the Judd Hill Plantation in northeast Arkansas. The research will determine the potential for water and energy savings and the economic feasibility of the technology. Instrumentation added to the center pivot system will determine if the system performed as intended, whether excessive pressure developed, and whether energy savings resulted from the modifications. Variable-rate water application will complement other precision-agriculture practices currently being used by US producers and lead to more efficient use of irrigation water.
Technical Abstract: Farms in the USA are typically larger than in many parts of the world. The combination of large farms and a small labor force have led US farmers to operate on a larger scale than their counterparts in many other countries. An example of large-scale irrigation equipment is the center pivot system, which consists of a series of self-propelled towers with irrigation sprinklers or spray heads mounted on a rigid pipe between the towers. One end of the system is stationary and the rest of the system revolves around the pivot point. A typical system is 400 m long (50 irrigated ha). With the exception of rice, practically all US-grown crops can be produced with center pivot irrigation. Although US producers have access to equipment for variable-rate application of most inputs, some of the potential benefit of precision agriculture may be masked by uniform application of irrigation water. While variable-rate water application is difficult with surface irrigation systems, center pivot systems can be adapted for variable rate water application. A system was developed at the University of Georgia to modify an existing center pivot system for variable-rate application, and water savings of more than 15% have been observed relative to the previous practice. The system was installed on 41 US center pivots at the time of this report, with one on a 400-m long system at the Judd Hill Plantation in northeast Arkansas (35° 36’ N, 90° 31’ W). The system was installed to demonstrate the technology to area farmers and allow study of the suitability of the technology on a working midsouthern US cotton farm. The objective of this research is to monitor the system to determine the potential for water and energy savings and the economic feasibility of the technology. The variable rate system divided the 400 m length into 24 independently controlled portions, such that the system can be divided into as many as 4,320 individually controlled management zones. To investigate the system, a replicated large-plot study was initiated in 2007 based on soil mapping units defined in the Soil Survey. Application rates were based on the farmer's practices, with one treatment being the farmer's application (typically 19 mm) and the others being 80% and 120% of the farmer's amount. The field will be harvested with the farmer's spindle-type cotton picker equipped with a yield monitor. Analysis of the yield monitor data will show whether the farmer would be better served to increase or decrease his water application rate. Instrumentation added to the center pivot system will monitor its performance to determine if the flowrate varied as it should, whether excessive pressure developed when portions of the system were turned off or pulsed, and whether the adaptations to the system resulted in energy savings. Variable-rate water application will complement the other precision-application practices currently being used by US producers and future studies are planned to investigate variable rate nitrogen application through the irrigation system and to address the economic feasibility of variable rate irrigation and/or chemigation.