Calibrating RZWQM2 model for maize responses to deficit irrigation

Parameterizing a system model for field research is a challenge and requires collaboration between modelers and experimentalists. In this study, the Root Zone Water Quality Model-DSSAT (RZWQM2) was used for simulating plant responses to water stresses in eastern Colorado. Experiments were conducted in 2008, 2009, and 2010 in which maize (Zea Mays L.) was irrigated to meet a certain percentage (100%, 85%, 70%, 55%, and 40%) of the estimated crop evapotranspiration (ETc) demand during a growing season. The model was calibrated with both laboratory-measured and field-estimated soil water retention curves (SWRC) and evaluated for yield, biomass, leaf area index (LAI), and soil water content under five irrigation treatments in all three years. Simulated results showed that field-estimated SWRC provided better model responses to irrigation than laboratory-measured SWRC. The results also showed that there were multiple sets of plant parameters that achieved acceptable simulations when only one irrigation treatment was used for calibration. Model parameterization can be improved when multiple treatments and multiple years of data are included. The parameterized RZWQM2 model was capable of simulating various irrigation treatments in all years and could be used to schedule irrigation based on ETc requirement.

► Field-estimated soil water retention curves are better than laboratory-measured ones in simulating crop response to irrigation water.
► Multiple treatments and multiple years of data should be used for model parameterization.
► RZWQM2 is capable of scheduling irrigation based on crop ET requirements.