Crop Water Production Functions of Grain Sorghum and Winter Wheat in Kansas and Texas

Abstract

AbstractProductivity of water‐limited cropping systems can be reduced by untimely distribution of water as well as cold and heat stress. The objective of this study was to evaluate the predictive accuracy of the Kansas Water Budget (KSWB) model for crop water use and grain productivity of grain sorghum and winter wheat grown in a range of crop sequences. The relationship of grain yield to crop water use, reported in several crop sequence studies conducted in Bushland, TX, and Colby and Tribune, KS, was compared against the KSWB modeling results. Field studies showed that the yield responses of grain sorghum to an increment of water use was generally 75% greater than that of winter wheat, as expected for crops with C4 and C3 physiology, respectively. The relationship of winter wheat yield to crop water use, simulated by the KSWB model, was comparable to relationships developed in four of five studies, with the exception of one study conducted in Bushland that suggested less crop water productivity. For grain sorghum, experimental yield response to an increment of water use was less than that calculated for three of five cases; for one study at Colby and Tribune, simulated and experimental yield response to water use were similar. Simulated yield thresholds were consistent with observed yield thresholds for both wheat and sorghum in all but one case. The KSWB model provides a useful analytic framework for distinguishing water supply constraints to grain productivity.