A Historical Perspective of VR Water Management for Improved Crop Production.

Variable-rate water management, or the combination of precision agriculture technology and irrigation, has been enabled by many of the same technologies as other precision agriculture tools. However, adding variable-rate capability to existing irrigation equipment design, or designing new equipment with built-in capability, posed a number of challenges and opportunities. Technical hurdles included design of variable-rate nozzles, nozzle flow rate and uniformity control, matching variable frequency drive controllers with irrigation pump systems, input from distributed sensors to inform control, and added system and management complexity. Economic benefits were not always apparent. Prototype variable-rate irrigation equipment was developed at a number of research locations represented in the author list, with substantial advances in research equipment during the 1990’s and early on-farm and commercial equipment during the first decade of the 2000’s. Much of the development and adoption paralleled the adoption of broader precision agriculture technology. This presentation will summarize technological developments in this field, provide examples of factors which steered the need for variable-rate irrigation, and summarize results from research on agronomic, economic and environmental outcomes. It will also provide an overview of the current state of the commercial art for variable-rate irrigation.