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The Upper Floridian Aquifer (UFA) is the main source of water for irrigation in the states of Florida and Georgia. Changing land use, crop management practices, increasing water demands for irrigation, and nutrient leaching can potentially affect the sustainability of agricultural production across the states. A wide variety of models can be used to determine loads of nutrients both in surface and groundwater as a result of crop management practices and irrigation. However, selection of a particular model depends on the level of detail required, the user needs and familiarity with the model, the model efficiency, and how intuitive is the calibration process. In this study, we summarize the main components and characteristics of three of the most widely used models for the prediction of nutrient leaching and crop yield. The Soil and Water Assessment Tool (SWAT), the Decision Support System for Agrotecnology Transfer (DSSAT), and the Agricultural Policy Environmental Extender (APEX) will be evaluated based on their effectiveness in predicting crop yield and soil water variables, such as, runoff, infiltration, potential evapotranspiration, soil and plant evaporation, and root water uptake. For the prediction of nutrients we will evaluate mineralization, immobilization, nutrient leaching, nitrification and denitrification variables. Preliminary results show that although all models have similar theoretical basis to calculate crop yield, soil water, and nutrient transport, DSSAT is more detailed in the representation of the plant physiological processes, SWAT emphasizes soil-atmosphere hydrological processes, and APEX is more detailed for the estimation of erosion processes and movement of nutrients from livestock. We expect the results of this preliminary study to be the baseline for watershed modelers and stakeholders to select the most appropriate model for nutrient leaching prediction at farm and watershed scale. |
