Submitted to: Irrigation Association Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/18/2013
Publication Date: 11/2/2013
Citation: Sui, R., Fisher, D.K. 2013. Evaluation of a center pivot variable rate irrigation system. In Proceedings of Irrigation Show and Education Conference.Irrigation Association Conference Proceedings. pp. 9.
Interpretive Summary: Application of variable rate irrigation (VRI) technologies has great potential for farmers to optimize crop yield and minimize environmental impact. The accuracy and uniformity of a VRI system are essential for the success of precision irrigation management. USDA-ARS scientists at Crop Production Systems Research Unit, Stoneville, MS evaluated a center pivot VRI system with both constant application rate and variable application rate. Under a constant application rate, a uniformity coefficient of 86.5% was observed, and the difference between the desired application amount and actual amount applied was 5%. The variable rate application test was conducted with five different application rates between 0 and 100%. The system performed well in zone control, and in general, the applied water depths followed the desired rate pattern. However, the effect of application rate on uniformity was significant. The variation in application rates between adjacent control zones was a gradual process instead of an ideally rapid change. This study was preliminary and more comprehensive evaluations on the VRI system performance are needed.
Technical Abstract: Uniformity of water distribution of a variable rate center pivot irrigation system was evaluated. This 4-span center-pivot system was configured with 10 water application zones along its 766 ft-long lateral. Two experiments were conducted for the uniformity tests. In one test, a constant water application rate (100%) was applied, and in the other, variable application rates (0%, 30%, 50%, 70%, and 100%) were assigned to each zone. To catch water applied, multiple water collectors were placed in two straight lines perpendicular to the pivot travel direction. Three control collectors with known amounts of water were placed at the test site to account for water evaporation losses during the tests. Water caught in the collectors was measured, and the center pivot coefficient of uniformity (CUH) was calculated. Results showed a CUH of 86.5% for the constant application rate test. The effect of application rate on CUH was significant, with higher application rates providing higher CUH values.