A geographic information system was used to demonstrate a methodology for assignment of best management practices that integrate land capability and crop suitability zoning on an agricultural watershed on St. Lucia. Primary parameters used in determining land capability included slope steepness and soil stability. Land capability classes were delineated, and recommended agricultural, agro-forestry and forestry prescriptions were assigned across the watershed. Crop suitability over the watershed was analyzed for selected tree crops, using fiizzy-set membership to represent variability in slope, rainfall and soil parameters in crop growth. The procedures developed in this study will contribute to a spatially-based decision support system toward conservationoriented agricultural and forestry land planning on St. Lucia. The study demonstrates the effectiveness of GIS in the application of spatial modelling procedures in rapidly evaluating watershed management strategies.