DSSAT is a microcomputer software program combining crop soil and weather data bases and programs to manage them, with crop models and application programs, to simulate multi-year outcomes of crop management strategies.

We have published a link between DSSAT and SimRoot 4. You can find the article in this book:

Response of Crops to Limited Water By L. R. Ahuja, L.R. Ahuja, V.R. Reddy, S.A. Saseendran, and Qiang Yu, Editors, Crop Science Society of America, Soil Science Society of America, American Society of Agronomy

More information about the DSSAT model program