The GOSSYM-COMAX research team has developed software to simulate cotton growth and yield. The program is sufficiently well developed to be used by farmers for realtime decision support in planting date, water and nitrogen management, and defoliation timing. Near 150 farmers used the model in 1988 from California to North Carolina. USDA ARS and ES have chosen GOSSYM-COMAX as the initial crop simulation model to implement on the farm. Subsequent efforts to improve decision support in cotton and other enterprises are expected.