中国农牧系统养分管理研究的意义与重点

中国由于农牧分离和不合理的养分管理方式导致了农田硝酸盐淋失、水体富营养化、氨挥发和温室气体排放等环境问题日益严重。研究中国“土壤-作物-畜牧业”生产系统（即农牧系统）养分流动特征，通过优化农牧系统养分管理，保持养分合理流动与循环，减少各个环节的养分环境排放，提高系统利用率是农牧业可持续发展的关键，也可为“化肥减施”、“有机肥替代化肥”、“畜禽养殖废弃物资源化利用”和“面源污染阻控”等国家行动提供科学依据。本文对中国农牧系统养分投入、利用率和环境排放等特征、国内外农牧系统养分管理研究进展进行了分析，提出中国农牧系统养分管理研究重点。目前中国农牧系统养分流动特征是过渡依赖化肥养分投入提高粮食和饲料产量，进而支持集约化畜牧业发展；而农牧分离的生产方式导致了农牧系统养分流动效率低，环境排放高；都市圈及其周边是排放的热点区域。国际研究经验表明，农牧结合是可持续集约化农业的必然出路，农牧结合的核心是通过改善畜禽粪尿管理，减少养分的损失和提高养分在农田循环的比例和数量。兼顾提高农牧业生产力和保护环境的“土壤-作物-畜牧业”系统养分管理已经成为全球关注的焦点。未来，中国农牧系统养分管理研究应包括：（1）典型农作系统“土壤-作物-畜牧”系统养分流动规律和环境效应的定量研究；（2）有机肥替代化肥机理与调控途径研究；（3）畜禽粪尿养分循环利用机理和减排技术研究；（4）高产高效“土壤-作物-畜牧”系统设计研究。

Significance and Research Priority of Nutrient Management in Soil-Crop-Animal Production System in China

With a rapid development and decoupling between crop and animal production, China already faces serious groundwater pollution by nitrate leaching, eutrophication of surface waters, as well as air quality degradation caused by over-fertilization and manure discharge. It is important to (1) quantify nutrient flows in “soil-crop-livestock” production system, (2) optimize nutrient flows and recycling by coupling crop and livestock systems, and (3) mitigate nutrient losses and improve nutrient use efficiency. These studies provide a scientific basis for national action (e.g. reduction of chemical fertilizer application, replacement of chemical fertilizer by manure, resource utilization of livestock waste and mitigation of non-point source pollutions). The objectives of this study are to review the published studies on nutrient management in crop and animal production, analyze the characters of nutrient inputs, use efficiencies and losses of crop and animal production in China in the past decades, and to prospect research priority of nutrient management in soil-crop-animal production systems in China. For increasing productivities of grain, overuse of chemical fertilizer is common, lack of manure recycling. The biggest challenge facing China today is de-coupling crop and animal production. The nutrient use efficiency of crop and animal production decreased and nutrient losses increased dramatically in the past decades in China. The highest emissions are estimated in or around big metropolitans. Coupling crop and animal production is the main solution of sustainable intensive agriculture. According to the international research experiences, research should focus on improving manure management, mitigation of nutrient losses and increasing nutrients recycling rate of agricultural wastes. The integrated nutrient management of the soil-crop-animal production systems has become the focus of global concern. Key research topics of nutrient management in crop and animal production include (1) quantifying nutrient flows and environmental impacts of ‘soil-crop-animal’ production systems, (2) strategies of chemical fertilizer replacement by manure, (3) mitigation options of manure management from ‘feeding-housing-storage-treatment-application’ chain, and (4) farming system design for achieving high productivities and nutrient use efficiencies in crop and animal production.