Modeling maize production under growth stage-based deficit irrigation management with RZWQM2

Farmers are challenged to maintain yield and economic productivity with declining water resources and climatic variability in semi-arid regions worldwide. Growth stage-based deficit irrigation has been suggested as a feasible approach to maintain yields with less water. Experiments were conducted in 2012, 2013, and 2015 in which maize (Zea mays L.) was irrigated under twelve treatments with varied levels of deficit irrigation during the late vegetative (Lveg) and maturation (Mat) growth-stage periods in Northern Colorado. The Root Zone Water Quality Model 2 (RZWQM2)-CERES-Maize model was used to simulate the effects of growth stage-based deficit irrigation on maize production and yield components. The results showed that RZWQM2 could simulate the impact of temperature on maize phenology but did not simulate the impact of water stress on maize maturity. Both simulated and observed aboveground biomass, grain yield, and kernel weight decreased with the decrease of irrigation water amount during Lveg and Mat periods. In general, the simulated aboveground biomass and grain yield showed larger errors in terms of root mean squared error (RMSE), relative RMSE, and Nash-Sutcliffe efficiency, than those reported in the previous modeling studies where deficit irrigation was applied uniformly throughout the growing seasons in the same field. Future efforts to improve the effects of deficit irrigation on kernel development will likely make RZWQM2 a better tool for optimizing irrigation management in semi-arid regions.