Technical Abstract: Agricultural models and decision support systems are becoming increasingly available for a wide audience of users. The Great Plains Framework for Agricultural Resource Management (GPFARM) DSS is a strategic planning tool for farmers, ranchers, and agricultural consultants that incorporates a science simulation model with an economic analysis package and multi-criteria decision aid for evaluating individual fields or aggregating to the entire enterprise. As GPFARM is being expanded to include tactical planning, improvements are needed in the plant growth model, particularly for improvements responses to limited water. This paper presents the plan and approach for improving the crop and rangeland plant growth models. Six areas for improvements have already been identified: seedling emergence, phenology, biomass generation, biomass partitioning, root growth, and plant stress factors. Status of work on these areas are presented.