Abstract: Studies of soil structure and soil fertility in ridged paddy field and ridged piscicultural paddy field were carried out in comparison with traditional waterlogging paddy field in Sichuan province in 1987.Results showed increases in 0.01mm water-stable microaggregates and aggregation coefficient of 0.01mm soil particles. There was a tendency towards increase in mineral-cemented aggregate and deerease in soil potential fertility in ridged paddy field,but in ridged piscicultural paddy field, a significant increase in organic matter and a higher nutrient content and availability were observed because of the increase cf organic material-cemented aggregates,in which,Fe Al-humus cemented aggregates were dominant. With lime application and field sunning after fishing, high yield of rice could be reached without or with little fertilizer application.

Key words: Transgenic crops, Ecological risk assessment, Soil ecosystem, Soil microorganism, Soil fauna