稻-鱼系统的发展与未来思考

耕地和淡水是保证全球食物可持续供应所必不可少的资源,如何有效利用有限的水土资源、在保障食物供给的同时降低农业生产过程对资源环境的负面影响,是当今世界农业面临的重大挑战。稻-鱼系统(本文的"鱼"是水产生物的统称)是通过有效利用水土资源同时产出稻谷和水产品的重要农业方式,对保障区域食物供给和保护当地资源和环境有重要作用。近几十年来全球稻鱼-系统迅速发展,至目前全球六大洲的稻作区共28个国家都有了稻-鱼系统的分布;在中国稻-鱼系统也正由原来传统、规模小、养殖单一的模式逐渐发展为规模化、专业化、机械化和养殖多样化的模式。大量研究表明,稻-鱼系统可实现水稻产量稳定和获得水产品,稻-鱼系统同时具有化肥农药减量和农业面源污染降低等效应;稻-鱼系统也有助于解决水产单一养殖而产生的面源污染。虽然全球1.63亿hm2稻田面积90%以上具有发展稻-鱼系统的潜力,但目前稻-鱼系统的比例仍很低,我国稻-鱼系统面积也仅占稻田面积的4.48%。因此,保障稳产高效可持续的稻-鱼系统发展,需要对不同稻作区发展稻-鱼系统的生态经济可行性和适应性进行评估,同时必须建立新的技术体系(田间设施、种养结合技术、农业机械等),并适当扩大规模和创建品牌以增加农民收益。

Development of rice-fish system: Today and tomorrow

Land and freshwater resources are essential for ensuring global sustainable food supplies. The world agriculture currently faces great challenge on how to secure food supply with scarce land and freshwater resources without negatively impacting the environment. Rice-fish system (where 'fish' denotes a wide range of aquatic animals including fish, prawn, shrimp, crabs, soft shell turtles, etc.) is one of the successful models for producing both rice and fish by efficient use of land and freshwater resources. Rice-fish system has contributed to local food security, poverty alleviation and environmental conservation. In the last decades, rice-fish system experienced a fast development in the world. Recently, rice-fish system is practiced in 28 countries (including Japan, Egypt, India, Indonesia, Thailand, Vietnam, Philippines, Bangladesh, Myanmar and Malaysia). Rice-fish system has a long history in China and has played an important role in providing rice and fish for local consumption. Over the last 60 years, Chinese rice-fish system has steadily developed and changed from small-scale traditional farming to large-scale modern farming with specialization and commercialization to ensure sustainability. Studies have shown that rice-fish system can have high yields of rice and fish and thereby optimizes the benefits of scarce land and water resources as a result of complementary and synergistic interactions between fish and rice. Rice-fish system also decreases pesticide use due to lowering the incidence of diseases, insect pests and weeds in rice fields. Meanwhile, rice-fish system reduces nitrogen fertilizer application through complementary use of nitrogen by rice and fish, and enhances soil nutrient availability for rice crop. Rice-fish system also resolves certain problems induced by freshwater aquaculture because nutrients in effluents resulting from fish production are absorbed by rice crops and are therefore not wasted or would not become a pollution source. Although most areas of global rice fields are suitable for developing rice-fish system, the adoption rate and scale of rice-fish system in the world remain low. In China, there is only 4.48% of the total well-irrigated rice paddies co-cultured with fish. Therefore, to ensure sustainable development of rice-fish system, more efforts are needed. These efforts include: 1) potential assessment of rice paddy for rice-fish system (e.g. water supply and water quality in rice fields), evaluation of new fish species for rice field culture and selection of rice varieties for rice-fish co-culture; 2) development of technology packages for culturing rice and fish, optimization of fertilization rates and fertilization methods for rice and optimum feeding rates and methods for fish; 3) developing field configurations for rice culture and aquaculture; 4) optimization of rice planting patterns for rice-fish farming, determination of the carrying capacity and optimization of stocking densities; 5) development of suitable machines for rice-fish system; and 6) assisting farmers to create identity product brands acceptable to consumers and society.