Abstract
A parametric crop water use and yield model was applied to a transect spanning the North American Great Plains to investigate the evapotranspiration demand on grain corn and the associated irrigation water applications needed for optimal crop production. The transect consisted of four sample stations, covering 25 degrees of latitude. 124 climate change scenarios for each of the transect stations, were created by systematically changing air temperature, precipitation, and incident solar radiation in terms of positive and negative departures from the normal, long-term record. This paper reports how grain corn evapotranspiration and irrigation water amounts would respond to climatic changes inherent in the scenarios if there were no changes in agricultural technology. Among the results, the seasonal response of evapotranspiration (ET) totals to air temperature perturbations was greatest in the higher latitudes and least in the lower latitudes. This impact of changing temperature was also greatest under sunny compared with cloudy conditions, and for fully irrigated in contrast to rainfed conditions. Changes in precipitation amounts caused greatest responses in rainfed fields under sunny conditions. The middle latitudes (e.g., Kansas City) were most sensitive. Perturbing solar radiation caused greatest evapotranspiration changes with irrigated conditions particularly in the middle latitudes. Percentage changes in solar radiation (or cloudiness) were of considerably greater importance than comparable precipitation changes. In the absence of temperature perturbations, the relative precipitation and solar radiation changes caused similar trends in amount of irrigation water applied. For temperature changes, the resultant irrigation watering responses were largely non-linear. A consecutive paper will report on the response of maize yield to the introduced climatic changes and associated irrigation schedules.
Published Version
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