Economic Optimization of the Levels of Control in Variable Rate Irrigation (VRI)

Abstract

Abstract. Water scarcity and rising energy costs make variable rate irrigation (VRI) an appealing irrigation strategy. Center pivot irrigation systems can be equipped with different levels of VRI control including angular speed control and circular zone control. In this study, an economic optimization model was developed to determine the optimal level of VRI control to maximize the expected net return over the cost of irrigation for a specific crop production setting. To demonstrate the model‘s application, apparent soil electrical conductivity (ECa) and topographic maps of a 20 ha wheat field in Southern Alberta were used. The ECa map was used as a proxy of soil water storage potential (WSP), and field topography was used to impose the effect of water-logging on yield decline under surplus irrigation. Economic assessment of 62 irrigation management scenarios included: 1) no irrigation (NI), 2) uniform irrigation management (UM), 3) VRI speed control (SC) with two angular increments, i.e., 2° and 10°, and 4) VRI zone control (ZC) with a combination of two angular increments and a different number of independent irrigation rate zones, ranging from 2 to 30. This model showed that the most advanced VRI ZC with 2° angular increments and 30 control zones produced the highest profit over cost of irrigation. However, taking into account the cost of technology, 10 control zones along the center pivot irrigation system were found to be the most profitable option. The model inputs included ECa and elevation maps, boundary conditions for yield response to irrigation, cost of irrigation water, supply energy, crop, and irrigation system equipped with different levels of VRI control.