Linking the Unified Plant Growth Model (UPGM) with the Agroecosystems-Watershed Model (AgES-W).

Agricultural models and decision support systems (DSS) for assessing water use, land use, and management are increasingly being applied to diverse geographic regions at different scales.   The AgroEcoSystems-Watershed (AgES-W) model is a component-based model for simulating soil-plant-water-nutrient processes in a spatial context of multiple hydrologic response units (HRU’s) that are simulated simultaneously.  AgES-W requires a plant growth model that can simulate many common and alternative crops for each HRU, however, very few plant growth models are available that can “easily” do this.  One option available is a suite of plant growth models based on the original plant growth model used in EPIC (Environmental Policy Integrated Climate Model).  Various versions of the original EPIC plant growth model have been used in other agroecosystem models such as the Soil and Water Assessment Tool (SWAT), Wind Erosion Prediction System (WEPS), Water Erosion Prediction Project (WEPP), ALMANAC, and the Great Plains Framework for Agricultural Resource Management (GPFARM) DSS.  While these versions are quite similar, slight improvements and changes have been made for specific model objectives.  Unfortunately, improvements to individual models have generally not been incorporated into the other models and several process algorithms need improvement to better simulate diverse environments and management practices.  This paper first discusses efforts to develop the Unified Plant Growth Model (UPGM) as the platform for incorporating different versions of the EPIC-based plant growth models and then improve specific sub-modules (e.g., phenology, seedling emergence, canopy height) for improved overall model performance.  Then progress linking UPGM with the AgroEcoSystems-Watershed (AgES-W) model, as a replacement of the currently used SWAT-based plant growth model, is discussed.