Water is one of the most important factors influencing crop production in rainfed cropping systems. In tropical regions, supplemental irrigation reduces the risk of yield losses associated to water deficit due to insufficient rainfall. The negative effects of water deficit in regions with irregularities in rainfall may be minimized with the use of supplemental irrigation, a technique based on the application of water at amounts below the crop's evapotranspiration (ETc). We investigated the potential of supplemental irrigation as a strategy to increase yield of maize grown under tropical conditions. We used the CSM-CERES-Maize model of the Decision Support System for Agrotechnology Transfer (DSSAT) to simulate irrigation strategies of maize in six counties in the state of Minas Gerais, Brazil. Our results indicate significant differences on simulated crop yield in response to water. Our results also indicate improves on water productivity in some locations with 10% and 15% less water than that from full irrigation.