Crop simulation models have been recognized as useful tool for crop management. However, the application of models under drought condition has not been extensive because of the failure of models to accurately simulate plant growth and yield under these conditions. Such failure is mainly due to simplified simulation of soil water, heat transport and canopy energy partitioning processes. With advanced computer technology and improved understanding of soil-crop-atmosphere system, it is feasible to develop mechanistic models that could be used under wider range of climatic and soil conditions. The overall objectives of this research are: 1) to develop a comprehensive model of soil water, heat transport and canopy energy balance; 2) to couple this model with the existing crop growth model in ICEMM (Integrated Crop Ecosystem Management Model); 3) to calibrate and validate simulations of soil water and heat transport, and energy partitioning processes, and the whole coupled crop growth and yield model by field experiments. In this paper, the development of the soil dynamics and energy partitioning processes model is described, and some preliminary results are presented. The numerical method used to solve the governing equations is Alternative Direction Implicit (ADI) finite difference scheme. Simulation results show that the model can simulate leaf water potential, leaf temperature, transpiration and soil water and heat transport reasonably well. This more mechanistic approach of the simulation of plant water status will improve the simulation of photosynthesis and organ elongation rate, thus leading to a better simulation of crop growth and yield. Further model development and validation will be conducted during the 1993 and 1994 growing seasons at Texas A&M Agricultural Experiment Station at Corpus Christi.