Variable Rate Irrigation: A Long‐Term Simulated and Field Data Analyses of Irrigation Practices, Field Variability, Economic Feasibility and Profitability

ABSTRACT

Long‐term economic analyses of variable rate irrigation (VRI) strategies were performed compared with uniform irrigation management (UIM) in a reference production field using the AquaCrop model. Five strategies to trigger irrigation were as follows: (Field Capacity‐VRI, Driest Soil Trigger‐VRI, Water Mining‐VRI, Conventional Uniform Irrigation Management (CUIM) and field‐averaged uniform method (Aggregated Uniform Irrigation Method, AUIM). Thirteen field distribution models were developed by varying the reference field's soil textures (the reference field had four different soil textures) to model field variability. Analyses were based on three cost factors (100%, 75%, and 50% of the current costs of VRI). Costs, feasibility, and profits were calculated considering irrigation strategies and field soil distributions. VRI was not feasible at present costs because an average annual irrigation reduction of 2.4% was not able to justify the 4% yearly loss as compared with CUIM, considering capital and operational costs. AUIM is a feasible strategy and showed $2907 annual savings with CUIM. VRI was effective in the field areas where water mining is practical, that is, fields with variability in high water holding capacity soils covering at least 60% of the field. A reduction of at least 25% in the initial costs was considered essential for VRI to be economically beneficial.