Use of a System Model for Irrigation Scheduling and Crop Water Stress Simulation in a Corn Field.

It is desirable to have an irrigation tool that is based on system modeling using actual soil and weather information. In this study, we evaluate the ability of the Root Zone Water Quality Model (RZWQM2) in scheduling irrigation based on crop reference evapotranspiration (ET) and in simulating crop water stress conditions under different irrigation treatments for corn. The experiment was conducted in 2008 in a field close to Greeley, Colorado with six irrigation treatments based on crop ET requirement. The model was calibrated for the full ET treatment and evaluated for the rest (85%, 70%, 55%, and 40% of crop ET). The model was also evaluated with both field and laboratory measured field capacity, two crop water uptake routines, two different crop water stress assumptions, and two crop growth modules in RZWQM2. Initial results show that RZWQM2 has the ability to schedule irrigation and to predict crop water stress once it is calibrated for the local conditions.