Simulation for Irrigation Management of Corn in South Texas

Interest is growing in applying simulation models for the South Texas conditions, to better assess crop water use and production with different crop manage-ment practices. The Environmental Policy Integrated Climate (EPIC) model was used to evaluate its application as a decision support tool for irrigation management of corn (Zea mays L.) in South Texas of the U.S. We measured actual crop evapotranspiration (ETc) using a weighing lysi-meter, soil moisture using a neutron probe, and grain yield by field sampling. The model was then validated using the measured data. Simulated ETc using the Hargreaves-Samani equation was in agreement with the lysimeter measured ETc. Simulated soil moisture generally matched with the measured soil moisture. The EPIC model simulated the variability in grain yield with different irrigation regimes with r2 value of 0.69 and root mean square error of 0.5 ton ha-1. Simulation results with farm data demonstrate that EPIC can be used as a decision support tool for corn under irrigated conditions in South Texas. EPIC appears to be effective in making long term and pre-season decisions for irrigation management of crops, while reference ET and phenologically based crop coefficients can be used for in-season irrigation management.