"Dual character" of rice-crayfish culture and strategies for its sustainable development

Rice-crayfish culture has been greatly developed in China in recent years due to its high comprehensive benefits. Especially, rice-crayfish culture has been rapidly developed in Hubei Province, where has a large area and proven technique of rice-crayfish culture, and developed the "Qianjiang Mode". In this paper, we introduced the characteristics and the development of rice-crayfish culture, and studied the production and ecological effects of rice-crayfish culture in Hubei Province by investigation, demonstration and long-term experiment. And the "dual character" of rice-crayfish culture was illuminated. The "dual character" of rice-crayfish culture was mainly reflected by the following phenomena. (1) Rice-crayfish culture stabilized food synergy, but favored crayfish over rice. Rice yield of rice-crayfish culture was increased by 4.63%-14.01% compared with conventional rice culture, and the rice quality was improved. But sometimes the rice yield was decreased due to the poor management for rice. (2) Rice-crayfish culture improved the soil fertility, but aggravated the soil gleization. The contents of readily oxidizable organic carbon (ROC), total N, total P and total K in soil of rice-crayfish field were higher than those of conventional rice field, but soil color was darker, structure was tighter, the gleization was obvious. (3) The rice-crayfish culture conserved water, but in some cases increased water consumption. The water use efficiency and water conserving capacity in field with high groundwater level were higher, but water consumption was increased by 50%-80% in field with low groundwater level. (4) The rice-crayfish culture decreased fertilizers and pesticides application, increased water nutrient con-centration, but also increased the risk of water eutrophication. The costs of fertilizers and pesticides were decreased by 79.5% and 50.0%, respectively. The total N, total P, nitrate-N and ammonia-N concentrations were higher in the surface water of rice-crayfish field. (5) The pests amounts were deceased, but some disease occurrence increased and biodiversity changed in rice-crayfish field. The lepidoptera pests were decreased, but the basal rot was heavier, and the biodiversity was decreased firstly, then increased by years in rice-crayfish culture. Finally, we made some suggestions for improving the rice-crayfish culture, such as adjusting managements to local conditions and decreasing blindness, standardizing development, optimizing pattern and regulating water and fertilizer utilization, and scientific control of disease, pests and weed. These suggestions may ensure the sustainable development of rice-crayfish culture.