As a contribution to a long—term evaluation of the sustainability of agro—ecosystems in the Yuanyang rice terraces, this paper reviews the bio—physical environment of the terraced landscape in a small catchment around Qingkou village and assesses soil fertility in the village crop growing area. A soillandscape organization pattern was developed using a geomorphopedological approach. Anthropogenic, climatic and topographic factors were identified as the main soil forming factors. Soil capability and associated edaphic constraints were assessed and the main soil types were identified and classified using FAO protocols. Spatial patterns of soil fertility appear quite homogeneous. Soils are acid and cation exchange capacity and nutrient reserves are generally low. The agro—ecosystem has largely been developed by the Hani population. This agro—ecosystem has succeeded in maintaining a relatively dynamic nutrient circulation system. Current research is focusing on: (i) the evaluation of the representativeness of the studied area compared to the whole terraced system in the Yuanyang terraced landscape; (ii) measurements of nutrients flows at the field scale! (iii) the effects of soil properties on crop yields; and (iv) up—scaling field levels results to larger spatial units.