Effect of rice-azolla-fish system on soil environment of rice field.

The basic technique of rice-azolla-fish system(RAF) is to combine azolla and fish into traditional rice farming system, and thus to realize the artificial management of the ecosystem via a throughout controll of azolla and fish in paddy field. Under the comprehensive reaction of various practices, the fish yield in rice-azolla-fish sys-tem maintains 4.0 to 9.8t/hm2, and its rice yield has increased to compare with the traditional farming system in the condition which decreased 50%-60% chemical fertilizer and 30%-50% pesticide. The result of long-term determination demonstrated that, organic matter, total N and P in ecosystem accumulated year by year, being 15.6%-38.5% higher than that in the traditional farming system. The pest and disease of rice were decreased by 40.8%-99.5%, the methane emission was decreased by 34.6%, the paddy field eco-environment was improved.