Study On Ecological Characteristic And Technique For Safe,Good Quality And High Benefit Of Rice-fish Culture

Rice-fish culture is a complex ecological agriculture mode which combines the culture of rice with culture of economic aquatic such as crabs, shrimps, fish, etc. Since 1990s, the rice-fish culture area has risen rapidly, and it has become an important part in the adjustment of agriculture industrial structure. As the development of other ecological agriculture hi China, although there were some advantages in production practice of rice-fish culture, most were still based on production experimence, it was still lack of normalized knowledge. The degree of scientific production and standardization was still lower. The quality of rice and aquatic products was not good and the production was not stable, which was not favorable to the further strengthening and development of technique and production. Therefore, to strengthen the scientific experiment and systematic study of eco-agricultural system in rice-fish culture and to set up theoretical and technique system for safe, good-quality, high-benefit rice-fish culture were becoming an urgent and important subject for the rice and fish researchers. Based on the survey of rice-fish culture status in Jiangsu Lixiahe area (Xinhua) where the rice-fish culture was the most concentrated and the biggest culture area, this research studied the characteristics and related technique system of the ecological environment, rice, crabs (shrimps, fish, etc.) in rice-fish culture. It put forward the optimized synchronizing mode for rice-fish culture. The technique benefit was also assessed and a preliminary criterion for safe, good-quality, high-benefit rice-fish culture has been set up. The main results were showed as follows:1. Compared with the conventional ecosystem in paddyfield and fishpond, the rice-fish ecosystem has the following ecological characteristics in systematic structure and function, physical and chemical property of water and soil, substance flow energy, etc.: the system showed the ecological diversity in horizontal and vertical structure, formed the water environment from rice farmland, deep down to farmland channel, surrounding channels and temporary channels. So that it provided crabs and shrimpswith the diverse ecological environment of growth and habitat, and the biological species were more abundant. The flow pathway of substance and energy increased and the food chain was strengthened toward more complexity. The resources could be fully used on different levels so that the efficiency of resources utilization was increased. Compared with the conventional paddyfield, the bulk density of rice farmland soil decreased, the soil saturation water content, field maximum holding water content and porosity increased, and the soil physical property improved. However, the soil redox potential could reduce, the alleviation of soil physical properties would be weaker with the year extension of rice-fish culture.The organic content and Nitrogen, Phosphorus, Potassium content rised, the soil fertility improved, and the alleviation effects could increase further with the extension of rice-fish culture. The supply of available N, P, K was better than that in the conventional paddyfield. The water temperature in the system varied with the season, diurnal and the vertical direction. The surface water temperature in farmland channels and rice farmland was lower than that in surrounding channels, it was a bit higher or close to that in the bottom level, and there was obvious vertical change in temporary and surrounding channels. The change was large during the day but small during the night, and it was not obvious in farmland channels and rice farmland channels. During the period of rice-fish culture, the temperature change hi rice-fish paddyfield was smaller than that in conventional paddyfield. The dissolved oxygen content in ecosystem was greatly influenced by solar radiation and oxygen generated by hydrophyte. Because of the weak sunlight and not much oxygen from plankton in the subsurface, it was significantly lower than that in surrounding channels, while hi deep water lay...