SIMULATION OF VARIABLE WATER APPLICATION WITH LINEAR-MOVE IRRIGATION SYSTEMS

A linear-move irrigation system was recently installed at the Colorado State University Agricultural Research, Development and Education Center (ARDEC). This machine will be used for small plot studies emphasizing conjunctive management of irrigation water and chemicals for both protection of groundwater quality and optimizing production from limited water supplies. Because of the many small plots under the machine, it is necessary to control water and chemical applications both along the lateral line and in the direction of travel. Electrical solenoid valves are used to pulse the flow through sprinkler heads as a means of obtaining a wide range of application rates to plot areas. A simulation model for evaluating center pivot systems was adapted to simulate linear move systems operating under normal and pulsed conditions. Donut-shaped stationary water distribution patterns were added to the model to represent the distribution of low pressure sprinkler heads. The model was used to simulate the performance of the system under various pulsed conditions. Field evaluations were carried out to verify simulation results. A coefficient of uniformity exceeding 90% was obtained with a pulsing frequency of I cycle/min and a percent timer setting at less than 50%.