A six year's follow up monitoring program was accomplished on the fields in east Dongting lake. It was found that, at the same condition, for four main cropping systems had different effects on soil fertility.Rice rice system lead to low yield,a decrease and retrogression of soil fertility,Rice rice green manure system lead to yield increase to some extent and bring about good economical benefit. Under this system,soil fertility appeared an increasing and evolution trend.Rice rice wheat and Rice ric...