中国种养系统的氮流动及其环境影响

利用集成完全氮平衡模型和农业污染清单的中国种养系统氮流动模型(nitrogen flow model for farming-feeding system in China,NFM-FFS),研究了2003年中国种养系统中的氮流动及其环境影响.结果表明,2003年中国种养系统土壤虽然氮素表观盈余,但实际亏损623.9×104t,平均亏损13.7 kg/hm2,土壤整体面临含氮量减少和退化的风险.由于中国氮素投入(肥料和各类有机肥)主要集中于耕地系统,对牧草地的投入很少,耕地系统的氮素盈余了1 761.9×104t,平均盈余142.8 kg/hm2,中国牧草地系统氮素亏损2 385.7×104t,平均亏损90.7 kg/hm2.因此平衡耕地和牧草地的氮素投入既可减少农业生产对水环境的影响,又可有效控制牧草地退化.2003年,中国种养系统中总氮损失为2266×104t,其中随径流进入地表水的495.8×104t和淋洗进入地下水的102.4×104t最终沉积在河流、湖泊和海洋中,很少有机会再进入种养系统循环.耕地的肥料施用是中国种养系统向地表水和地下水最主要的氮输出源,应是农业污染控制和管理的重点.

Nitrogen Flow in Farming-Feeding System and Its Environmental Impact in China

By applying Nitrogen Flow Model for Farming-Feeding System (NFM-FFS) which integrates soil full nitrogen balance model with inventory analysis for agricultural pollution, nitrogen flow in China farming-feeding systems and its environmental impact are analyzed. In 2003, although surface nitrogen surpluses, nitrogen deficit in agricultural soil system in China is estimated to be 623.9×104t, and 13.7 kg/hm2 averagely, which implies that soils in China farming-feeding systems are at the risk of nitrogen content decline and potential soil degradation as a whole. With a intense nutrient input in arable land and no extra fertilizer input in grassland in China, there is a nitrogen surplus of 1761.9×104t, averagely 142.8 kg/hm2, while grassland has a deficit of 2385.7×104t, averagely 90.7 kg/hm2. As a result, existing negative impact of cropping activities on water environment as well as grassland degradation may be effectively abated by balancing nitrogen input between arable land and grassland. Total nitrogen loss from China farming-feeding system is 2266×104t, including 495.8×104t exported into surface water by drainage and surface runoff, and 102.4×104t into groundwater by leaching. Lost nitrogen is to be deposited in rivers, lakes and marine system, and is less likely to return to farming-feeding system. Fertilizer should be the priority of rural pollution control and management because of its dominant contribution to nitrogen export into water environment from farming-feeding system.