ARS | Publication request: Does Deficit Irrigation Give More Crop Per Drop?

Submitted to: Proceedings of the Central Plains Irrigation Conference
Publication Type: Proceedings
Publication Acceptance Date: February 1, 2010
Publication Date: February 24, 2010
Citation: Trout, T.J., Bausch, W.C., Buchleiter, G.W. 2010. Does Deficit Irrigation Give More Crop Per Drop?. Proceedings of the Central Plains Irrigation Conference.

Technical Abstract: DOES DEFICIT IRRIGATION GIVE MORE CROP PER DROP? Deficit irrigation can be an effective way to maximize economic returns when water supply is the limiting resource. The ARS Water Management Research Unit is conducting field studies to determine the water production functions for 4 crops common in the High Plains – corn, wheat, dry beans, and sunflower. Water production functions show the yield:water relationship, and thus the marginal productivity of water used for crop production. Two years of corn data indicate that the marginal productivity of irrigation water is fairly low (1.3 kg grain per cubic meter water) near full irrigation but increases with deficit irrigation, indicating the economic benefit of deficit irrigation. However, when the production function is based on consumed water or evapotranspiration, the marginal value of water is fairly high (3 kg/cubic meter) and fairly constant as the deficit increases. This implies that, in terms of consumed water, there is no economic advantage to deficit irrigation and farmer profits would likely be higher fully irrigating a portion of a field rather than deficit irrigating the whole field. Thus, it’s critical that water production functions be developed based on the relevant “unit” of water. When costs are based on irrigation water supply costs, irrigation application is the relevant unit. However, when farmers wish to sell or transfer water to other purposes, the relevant unit in the western U.S. is water consumed.