Selection of end gun and optimization of water distribution under a center pivot irrigation system

When a center pivot irrigation system is adopted in a square field, its four corners cannot be irrigated. Therefore, an end gun is often installed at the end of the system to expand the irrigated area; as such, proper selection of the end gun and optimization of water distribution are essential. In this study, we assessed the water distribution characteristics, application accuracies and uniformities under a three-span center pivot with an overhang and end gun without a boost pump. Two typical low-pressure sprinklers of Nelson R3000 and D3000 at two common operating pressures (0.15 and 0.20 MPa) and three representative nozzle diameters (8.73, 10.32, and 11.91 mm) of the end gun (Nelson P85A impact sprinkler) were considered. Additionally, the effects of various factors on the water distribution uniformity and accuracy were evaluated, and the optimal operating parameters of the center pivot with the end gun were proposed. Regardless of whether the end gun was on, the water application uniformity and accuracy of center pivot with R3000 sprinklers were highly significantly (P0.05) inversely proportional to the operating pressure. Taken together, the end gun nozzle diameter of 11.91 mm at an operating pressure of 0.15 MPa under the center pivot with R3000 sprinklers was recommended. This study provides a scientific basis for the optimal design of a center pivot with an end gun for a square field.