Estimating irrigation water use for maize in the Southeastern USA: A modeling approach

Increased crop production and expansion of irrigated acreage in the southeastern USA have increased agricultural water use during the past two decades. To optimize irrigation water use, it is important to know when to irrigate and how much water should be applied. The objectives of this study were (1) to evaluate the Cropping System Model (CSM)-CERES-Maize model with measured data of the amount of water required for supplemental irrigation and (2) to apply the CSM-CERES-Maize model for estimating irrigation water use for maize in the southeastern USA. The CSM-CERES-Maize model was evaluated for 2000–2004 for five counties that represent the dominant maize production regions in South Georgia. For each county, historical daily weather data, three representative soil profiles, and specific crop management recommendations were used as input for the model. The simulated results were then compared with observed data obtained during the same period. The amount of water required for irrigation for each growing season was simulated for 58 years using historical weather data from 1950 to 2007 for 88 selected counties that corresponded to the most important agricultural production region in Georgia. Both monthly and annual water demand for maize was determined for each county. The total seasonal amount of water required for irrigation across counties and years ranged from 136 to 281mm, with an average of 227mm. The irrigation requirements among months varied from 10 to 79mm, with the highest amount required for May. The results from the evaluation showed that the model was able to simulate the amount of water required for maize irrigation in good agreement with the observed data. This demonstrated the potential application of the CSM-CERES-Maize model as a tool for estimating water demand for irrigation. The estimated water requirements for supplemental irrigation can be used by both policy makers and local farmers for planning the amount of water required for supplemental irrigation as well as for improvements in irrigation management for water conservation.