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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Production Systems Research » Research » Publications at this Location » Publication #293557
Title: Field test of a center pivot irrigation system

Author
item Sui, Ruixiu
item Fisher, Daniel

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2014
Publication Date: 3/9/2015
Citation: Sui, R., Fisher, D.K. 2015. Field test of a center pivot irrigation system. Applied Engineering in Agriculture. 31(1):83-88.

Interpretive Summary: For sustainable water use in agriculture, increasing water-use efficiency in agricultural production has become a serious issue. Compared to furrow-irrigation method, a sprinkler variable rate irrigation (VRI) system may significantly improve water-use efficiency by using precision irrigation technology. However, water application accuracy and uniformity of a VRI system are essential for the success of precision irrigation management. Currently there is no standard method for testing the uniformity of a VRI system. The scientists at USDA-ARS Crop Production Systems Research Unit, Stoneville, MS evaluated water application accuracy and uniformity of 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%. In the variable-rate test, 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. Uniformity of a control zone could be influenced by the overlap of sprinkler coverage between the adjacent control zones. The sprinkler coverage and spacing should be considered in establishing irrigation management zone. Results and knowledge gained from this study could be useful in development of a standard method for evaluation of center pivot VRI system, and benefit VRI research.

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 233 m-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. In variable rate test, the highest CUH of 89.2% was obtained in the zone with 100% application rate. Effect of application rate on CUH was significant, with higher application rates providing higher CUH values. The uniformity of a control zone could be influenced by the overlap of sprinkler coverage between the adjacent control zones.