LAUSR

Abstract A calibrated and validated Decision Support System for Agro-technology Transfer – Cropping System Model (DSSAT-CSM), CERES-Maize, was used to (1) evaluate maize (Zea mays L.) yield and water productivities (WP) under various irrigation frequencies (IRF) triggered by different plant available soil water (PASW) on three soil types, and (2) assess the optimum IRF and PASW triggers for maximum yield and water productivity on three different soils (with a depth of 1.2 m) in Finney County, Western Kansas. The treatments were four IRF (2, 4, 7, and 9 days), four PASW (5%, 25%, 50% and 75%) irrigation trigger and three soil types with a total of 48 combinations. The model was set to automatically apply 25 mm irrigation at selected day intervals when certain irrigation triggering PASW conditions were met. This study showed that maintaining higher PASW up to 75% or above might result in too many irrigations per season, which could be costly. IRF-9 showed substantially lowest yield under most PASW tested in this study. The highest yield was simulated at irrigation amount of 400–450 mm and ET of 650–800 mm depending on soil types. The highest irrigation water productivity (IWP, 30–33 kg/ha/mm) was simulated when triggered by 25% and 50% PASW for Ulysses silt loams. Overall, IRF-4 under 50% PASW threshold provided the maximum maize yield and WP for all soil types.