Deficit irrigation strategies for the western U.S.

Authors: TROUT, T - COLLABORATOR; HOWELL, T - COLLABORATOR; ENGLISH, M - OREGON STATE UNIVERSITY; MARTIN, D - UNIVERSITY OF NEBRASKA

Submitted to: American Society of Agricultural and Biological Engineers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2020
Publication Date: 11/1/2020
Citation: Trout, T.J., Howell, T.A., English, M.J., Martin, D.L. 2020. Deficit irrigation strategies for the western U.S.. American Society of Agricultural and Biological Engineers. 63(6), 1813-1825. https://doi.org/10.13031/trans.14114.
DOI: https://doi.org/10.13031/trans.14114

Interpretive Summary: Deficit irrigation is widely considered a way to maximize net income for producers by irrigating less than the full crop water demand. In most cases, deficit irrigation reduces yield and gross income, so this income loss needs to be offset by the value of the saved water. This articles discusses a situation where the manager is trying to maximize net income, is aware of water supply limitations and value, and has flexibility to adjust irrigated area and production inputs under either "land-limited" or "water-limited" constraints. We found that when production costs are appropriate for anticipated yields, net income is less sensitive to deficit irrigation planning decisions. As a result, producers can adjust deficit irrigation strategies for other management objectives, such as risk reduction, without reducing net income. Deficit irrigation will become more important as irrigation water supplies continue to decline in the future. Net income analysis can assist growers in making rational deficit irrigation decisions.

Technical Abstract: Competition for, regulation of, and depletion of water supplies in the western U.S. has resulted in reduced water available for irrigating crops. When the water supply is expensive or inadequate to meet full crop water requirements, deficit irrigation (DI) may maximize net income (NI) by reducing use of expensive water or irrigating more land with limited irrigation supplies. Managed DI entails rational planning and strategic water allocation to maximize NI when water supplies are constrained. Biophysical and economic relationships were used to develop NI models for DI and determine water allocation strategies that maximize NI under three types of water supply constraints. The analyses determined that potential benefits of DI are greatest when water is expensive, irrigation efficiency is low, the water supply is flexible, and rainfed production is not economically viable. When production costs are appropriate for anticipated yields, NI is less sensitive to DI planning decisions. Deficit irrigation will become more important as irrigation water supplies continue to decline in the future. Net income analysis can assist growers in making rational DI decisions.