有机农业能否养活中国?——氮肥供应获得的启示

Can organic agriculture feed China?Implications from the nitrogen supply

近年来,有机农业在全球得到了较快发展,然而对于其在农业中的定位和作用以及发展策略,尚存在较大争议。本研究从氮素供应角度,评估不施用化学合成氮肥对于中国粮食生产和消费的影响,以期为我国现代农业发展特别是氮素管理提供支撑。研究以中国整体农业生态系统为对象,基于共生固氮数量、农产品贸易对氮素供应影响以及粮食生产,分析在不同粮食消费水平情形下,有机农业能够养活的人口数量。研究发现,如果全部耕地按照有机方式管理,中国每年共生固氮量为15.41×10^(6)t。在不施用化学合成氮肥情形下,1979年和2018年粮食总产量分别为381.96×10^(6)t和420.72×10^(6)t。不考虑蔬菜和水果,分别能养活0.81×10^(9)~1.24×10^(9)人和0.50×10^(9)~0.77×10^(9)人,即中国耕地全部转化为有机农业方式,在当前耕地面积和科学技术条件下,难以养活全国人口。将进口农产品考虑在内,2018年实际人均粮食(折纯,不包括蔬菜和水果)消费量达689.35 kg·a^(-1)。减少食物浪费、调整食物结构和增加粮食特别是豆类进口,是解决中国粮食问题的重要举措,进口大豆等农产品对于中国化肥减量起到了重要作用。化学合成氮肥对中国粮食生产做出了巨大贡献,但氮素利用率仍有较大提升空间。有机和生态农业强调整体、协调、循环和再生,是引领中国农业可持续发展的理论基础和技术保障,在全国范围内应通过种养结合等措施促进养分的循环利用,降低资源浪费和环境污染。在政策和法律法规层面,可以通过生态补偿和种养循环等举措,提高氮素利用效率,实现粮食数量和质量安全以及生态安全等农业的多重目标。

In recent years,organic agriculture has been rapidly developed in China and throughout the world.However,the position and role of organic agriculture in overall agriculture and the corresponding development strategy of organic agriculture are still debated.From the perspective of nitrogen(N)supply,this study attempted to evaluate the effects of not using synthetic fertilizer N on foodstuff production and consumption and to provide technical support for N management in China.The study selected the whole agroecosystem in China and quantified the symbiotic N fixation,the impact of agricultural product on N supply and grain production,and the population fed under different levels of foodstuff consumption.The annual N fixation capacity of leguminous crops in China was 15.41×10^(6)t·a-1 if organic agriculture was adopted for all agricultural land.If no chemical N fertilizer was applied,the total agricultural product output in 1979 and 2018 was 381.96×10^(6)and 420.72×10^(6)t,respectively.These agricultural products(excluding vegetables and fruits)could feed a population of 0.81×10^(9)-1.24×10^(9)and 0.50×10^(9)-0.77×10^(9),respectively.Thus,if all agricultural lands were completely operated with organic agriculture principles and under the current acreage of agricultural land and science and technology levels,it would be difficult to feed the entire population of China.With consideration of the imported agricultural products,the actual per capita grain consumption(converted to standard grain,excluding vegetables and fruits)was 689.35 kg·a^(-1)in 2018.Reductions in food waste,adjusting the food consumption structure,and increasing grain imports are key measures for resolving the food security issues in China.The importation of soybeans and other agricultural products has played an important role in reducing fertilizer usage in recent years in China.Chemical N fertilizer has made a great contribution to grain production in China,but there is still room for improvement in N fertilizer efficiency.Organic and ecological agriculture emphasizes the principles of holistic,coordination,circulation,and regeneration,which is the theoretical basis and technical guarantee to promote sustainable agriculture that will play a dominating role in agricultural development.The integration of cropping with livestock production should be disseminated and implemented throughout China to reduce resource waste and environmental pollution.At the policy and legislative levels,ecological compensation,and crop integration with livestock production may increase N utilization efficiency and achieve multiple goals of agricultural development,including food security,food safety,and ecological soundness.