Water Supply: Yield Relationships Developed for Study of Water Management
2006
Stone, L.R. | Schlegel, A.J. | Khan, A.H. | Klocke, N.L. | Aiken, R.M.
The USA's west-central Great Plains is a semiarid region with irrigation largely from the Ogallala aquifer, which has experienced extensive water-level declines. Farmers respond to reduced water supplies with alternative management, irrigation equipment, and crops; and, it is imperative the economics of these changes be studied. Profit and risk in water management depend on the crop-water relationships. Our objective was to describe the development of, and tabulate, yield-water supply relationships for six primary crops of the region: alfalfa (Medicago sativa L.), corn (Zea mays L.), grain sorghum [Sorghum bicolor (L.) Moench], soybean [Glycine max (L.) Merr.], sunflower (Helianthus annuus L.), and winter wheat (Triticum aestivum L.). Soils were deep silt loams that developed from loess. Input weather data were long-term, daily means of air temperature, solar radiation, and precipitation. Crop growth patterns were consistent with full-season cropping. Yields modeled with the Natural Resources Conservation Service (NRCS) net irrigation requirement (NIR) for 80% chance rainfall ranged from 92 to 97% of the maximum yields. This illustrated that if net irrigation exceeds the recommended NIR, there will be no appreciable yield increase. These calculated yield vs. water supply results will aid in studying water resource optimization and the associated economics.
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