Development of Clemson variable-rate lateral irrigation system

Crops in the Southern United States are generally produced in fields which are known to have a high degree of variability in soil type, water holding capacity, infiltration rates, and other major factors which affect crop production. In these fields, the ability to turn irrigation water on or off or apply variably to different segments of the field is advantageous over the conventional uniform application. A variable-rate lateral irrigation (VRLI) system was developed for site-specific application of water to match field variability. The system consists of solid-state relays controlled by custom software, air-actuated diaphragm valves, a forward speed control system and a GPS receiver. The Clemson VRLI system applies variable-rate water utilizing the nozzle-pulsing technique and variable speed control system. This system could monitor and apply water based on the actual soil moisture content, pan evaporation data, or the U.S. Climate Reference Network (CRN) data. Uniformity tests show that the system is able to control the irrigation rate from 0 to 2.5 cm of irrigation water and can control the forward speed between 145 and 29 m/h. The pulsing technique to deliver variable amounts of irrigation had little adverse effect on system uniformity and nozzle flow rate with an average application error of less than 2%.