SITE-SPECIFIC SPRINKLER IRRIGATION IN A WATER-LIMITED FUTURE

Available water supplies for irrigation are becoming more and more limited in the western U.S. and other locations around the world, and this downward trend is accelerating. These issues will force major changes to physical and managerial aspects as well as the design of water delivery and on-farm irrigation systems. Thus, a water- and energy-limited future will be the likely catalyst that finally brings many of the existing precision agricultural technologies together for irrigated agriculture. Resource conservation as well as achieving environmental benefits will probably require the adoption of non-uniform water applications, also known as site-specific irrigation, for many growers. The goal of site-specific irrigation is to conserve water by directing the amount and frequency of water applications according to established spatial and temporal crop water requirements. However, more than 20 years of private and public research on site-specific irrigation has resulted in very limited commercial adoption of the technology. The current state of the art of site-specific center-pivot and linear-move sprinkler irrigation is reviewed Several general barriers to adoption of the technology and various knowledge gaps are identified. The primary reason for the very low rate of commercial adoption appears to be the absence of a market for the technology and a low rate of return. Documented and proven water conservation strategies using site-specific sprinkler irrigation for crop production are quite limited, and its cost-effectiveness has not been demonstrated. Simulation studies comparing conventional and site-specific irrigation have reported water savings of 0% to 26% for well-watered crop production, and the greatest savings are most likely to occur in humid climates by spatially maximizing utilization of non-uniform growing season precipitation. In arid and semi-arid climates, the greatest potential water savings could come from highly managed deficit irrigation strategies in which spatial management of soil water deficit timing is used to maximize net return rather than yield Future research needs to focus on developing and documenting cost-effective site-specific water conservation strategies to support market development for these advanced and needed irrigation technologies.