Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2017
Publication Date: 4/8/2017
Publication URL: http://handle.nal.usda.gov/10113/5725425
Citation: Trout, T.J., DeJonge, K.C. 2017. Water productivity of maize in the U.S. high plains. Irrigation Science. 35(3):251-266.
Interpretive Summary: Water shortage in arid and semiarid regions constrains irrigated crop production. Maximizing productivity per unit water use is critical to maintain food production and rural economies. USDA-ARS carried out crop water productivity trials between 2008 and 2011 at the Limited Irrigation Research Farm in the U.S. Central High Plains near Greeley Colorado. Corn yield declined with deficit irrigation, but the relationship was curvilinear with decreasing marginal productivity with increasing irrigation amount. This implies that although full irrigation that meets crop water requirements will provide maximum yield, crop water productivity (yield per unit water applied or consumed) may increase with deficit irrigation. Management decisions on area to plant and irrigation water to apply depends on economics including costs of production, costs of water, and how irrigation return flows are valued.
Technical Abstract: Maize water production functions measured in a 4 year field trial in the U.S. central High Plains were curvilinear with 2.0 kg m-3 water productivity at full irrigation that resulted from 12.5 Mg ha-1 grain yields with 630 mm of crop evapotranspiration, ETc. The functions show decreasing yield but relatively constant water productivity up to 25% ETc reduction. Water productivity declined rapidly with ETc reductions greater than 25% and was zero at about 40% of full ETc because about 250 mm of ETc was required to produce the first unit of grain yield. Although deficit irrigation may result in increased irrigation water productivity when irrigation application is restricted, reduction in irrigated area will often provide higher net returns if water consumption in terms of ETc is restricted. Water productivity should be based on ETc rather than irrigation water applied. Water balance techniques adequately estimated ETc when precision irrigation was carefully scheduled and seasonal precipitation was low.