Simulating Soybean Water Stress Effects with RZWQM and CROPGRO Models

Abstract

The Root Zone Water Quality Model (RZWQM) and CROPGRO‐Soybean simulate soybean [Glycine max (L.) Merr.] growth, development, and yield. The models require calibration for soybean grown in the specific environmental conditions of the central Great Plains before any long‐term assessments can be made of dryland soybean yield potential under the highly variable precipitation patterns of this area. The objective of this study was to calibrate and test RZWQM and CROPGRO‐Soybean for soybean growth, yield, and water use under a range of water stress conditions normally encountered by dryland production systems in the central Great Plains. Data from five experiments, each with four levels of water availability (20 data sets), were used to evaluate leaf area, plant height, aboveground biomass, evapotranspiration (ET), soil water extraction, and yield of soybean. Data from one water level of one experiment was used to calibrate the models, and the other 19 data sets were used as evaluation data sets. Both models correctly predicted the time course of volumetric water content, leaf area development, and plant and height biomass increase although RZWQM more accurately simulated water extraction in the lower soil profile. The decline in ET that is a result of decreased water availability was generally predicted well by both models. The models generally estimated the yield to within 10 to 15% of measured values. The models should be useful tools in evaluating the potential for soybean as an alternative crop in dryland rotations in the central Great Plains.