Computer control system for spatially varied water and chemical application studies with continuous-move irrigation systems

A microcomputer driven open-loop digital control system for implementing spatially variable water and chemical application from center pivot and linear-move irrigation systems is described. The control system is comprised of readily available commercial components and provides an effective means of implementing variable rate water and chemical application in crop production studies for evaluating potential benefits. The control system was implemented on a three-span 100 m linear-move irrigation system and on a 39-ha commercial center pivot irrigation system. Water and chemical application were monitored to document control system performance. The results show that spatially varied water and chemical application was achieved with the same accuracy as that of conventional uniform application. This paper provides details on the control system hardware and software and documents field performance. (C) 1999 Elsevier Science B.V. All rights reserved.