Designing for Deficit Irrigation

Deficit irrigation is the practice of deliberately under-irrigating a crop. This practice may be preferable to full irrigation when water supplies are limited or irrigation costs are high. This paper investigates the merits of deficit irrigation for a farm in eastern Oregon. Two distinctly different irrigation systems were designed, one for full irrigation, the other for deficit irrigation. The costs and performances of these two systems are compared. It is determined that the system designed for deficit irrigation could lead to increased farm income while substantially reducing energy, water and capital requirements. These advantages would be gained by designing the deficit irrigation system for long intervals between irrigations and for low soil moisture uniformity. It is concluded that deficit irrigation can offer significant benefits under some circumstances, these benefits may be largely dependent on system design, and a comprehensive economics analysis is required to accurately assess the merits of a deficit irrigation scheme.