Compensating inherent linear move water application errors using a variable rate irrigation system

Abstract

Continuous move irrigation systems such as linear move and center pivot irrigate unevenly when applying conventional uniform water rates due to the towers/motors stop/advance pattern. The effect of the gear drive/cart movement pattern on linear move water application is larger on the first two spans, which introduces errors on site-specific irrigation. Therefore, the objectives of this study were to model the linear move irrigation system cart movement and to develop an algorithm to compensate for unintended variable irrigation (application errors). The cart advance/movement modeling considered terrain attributes, average nozzle travel speed, and high frequency DGPS (differential global positioning system) cart positioning readings. This paper describes the use of an irrigation monitoring and control system, DGPS, GIS, and statistical analysis utilized in the modeling and compensation processes. The irrigation monitoring and control system was composed of a single board computer, a relay board controller, DGPS, electric solenoid valves, wireless ethernet bridge units, high frequency spread spectrum radios, as well as in-line and in-field sensor networks. This technology allowed for continuous, real-time data acquisition and irrigation system management through the internet. This study has shown that irrigation application errors were reduced from over 20% to around 5%, in the subsequent irrigation event.