Yield–Water Supply Relationships of Grain Sorghum and Winter Wheat

Agricultural sustainability in the USA's west‐central Great Plains depends on efficient use of water—the primary yield‐limiting factor in the region. With perennially water‐short status, the efficient capture and storage of precipitation in soil, and the yield responsiveness of crops to water, are emphasized. Our objective was to quantify grain sorghum [ Sorghum bicolor (L.) Moench] and winter wheat ( Triticum aestivum L.) yield responses to stored soil water and precipitation by using data gleaned from research conducted from 1973 to 2004 near Tribune, KS on Ulysses silt loam (fine‐silty, mixed, superactive, mesic Aridic Haplustolls) and Richfield silt loam (fine, smectitic, mesic Aridic Argiustolls) soils. Soil water content was measured gravimetrically to the 183‐cm depth at crop emergence. Grain yield was related to available soil water at emergence (ASW e ) (increased 221 kg ha −1 cm −1 in sorghum and 98 kg ha −1 cm −1 in wheat). Grain yield was also related to in‐season precipitation (ISP) (increased 164 kg ha −1 cm −1 in sorghum and 83 kg ha −1 cm −1 in wheat). From response‐surface analyses, 63% (sorghum) and 70% (wheat) of variations in grain yield were explained by variations in ASW e and ISP. In data sorted by tillage, yield response to water supply (WS) was greater with no‐till than with conventional tillage in both crops (184 vs. 129 kg ha −1 cm −1 in sorghum; 138 vs. 86 kg ha −1 cm −1 in wheat). This finding supports the concept that less tillage and more residue lead to more efficient use during the growing season of ASW e and ISP.