Zhong Linying, a farmer in Qixing, practiced monoculture of nile tilapia in a late ricefield and produced 3200 kg of fish per hectare. In 1986, this production system was extended in Dongshang Township. In 1987, results were obtained from five households in Dongshan Township. In contrast, an adjacent field that was the same size but had no fish had an output that was 3.15 times lower in value. The rice fish system is an artificially controlled ecosystem in which rice and fish coexist, depend on, and promote each other.
Fish play several roles in the system.
Weed control and preservation of soil fertility. In the ricefield, weeds compete with rice for nutrients, land, water, space, and sunlight. As a result they greatly affect the growth of the rice plants. In the rice fish system, weeds are eaten by grass-eating fish and their waste becomes a field manure that helps conserve and enrich soil fertility. Huang Xinlian, a farmer of Shuiyan Township in Shangyou County, adopted the rice fish system with a ditchpond for 3 years.