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Performance Evaluation of a Center Pivot Variable Rate Irrigation System

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131620776,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   Arndt Gossel, Allen L Thompson, Kenneth A Sudduth, Joseph C Henggeler
Keywords:   Variable Rate Irrigation Center Pivot Uniformity VRI

Abstract. Variable Rate Irrigation (VRI) for center pivots offers potential to match specific application rates to non-uniform soil conditions along the length of the lateral. The benefit of such systems is influenced by the areal extent of these variations and the smallest scale to which the irrigation system can respond. In this study, the VRI control system of a Valley 6000 center pivot was tested for uniformity and desired application. The purpose was to validate the ability of the concept rather than to conduct an exhaustive set of comparisons. Application collectors were spaced at uniform intervals of approximately 3 m along five to seven radial lines. The pivot was equipped to vary water depth in up to six separate application zones along the lateral. Uniformity tests were conducted in accordance with ASABE Standard S436.1. Wind speed was measured during all tests. Sprinklers were Nelson 3000 Spinners with wetted diameters of approximately 9 m. Suspended drop tubes positioned sprinklers approximately 2.5 m above the ground. Solenoid rates were varied from 40% to 100% in 20% increments. Results indicate that the system was capable of uniform application, though it was calculated with lower uniformity for the VRI tests than that of non-VRI tests. There was a gradual change of application depth along the lateral rather than an abrupt change between adjacent zones, reducing the uniquely managed areas. As expected, uniformity of application near towers was diminished.

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