Instrumentation for Variable-Rate Lateral Irrigation System

Abstract

Crops in the Southern United States are generally produced in fields which are known tohave a high degree of variability in soil type, topography, water holding capacity and other majorfactors which affect crop production. Therefore, conventional, uniform-rate overhead irrigationsystems tend to over-apply or under-apply water to the crop. A variable-rate lateral irrigation systemwas developed for site-specific application of water to match crop needs. This system is able tomonitor and apply water based on the actual soil moisture content, pan evaporation data, or the U.S.Climate Reference Network (CRN) data. Information from the moisture sensors, evaporation pan andCRN is acquired using wireless technology. A GPS receiver is used to determine the position of thelateral irrigation system in the field. A variable speed control system allows the irrigation system tomove quickly over wet spots and slow down over dry spots. The lateral irrigation system is controlledby the nozzle-pulsing technique for variable-rate water application. The nozzle pulsing technique toadjust irrigation rate worked very well. The average water application rate error was less than 2%.There was a strong correlation between soil electrical conductivity (EC) and soil water holdingcapacity. Therefore, the EC measurements could be used for irrigation scheduling decisions.