北京市农田生态系统氮素养分平衡与负荷研究——以密云县和房山区为例

为揭示北京市农田生态系统氮素养分平衡与负荷状况,利用物质流分析中"输入=输出+盈余"的物质守恒原理,以氮素养分为介质建立农田生态系统氮素平衡模型.根据北京地区密云、房山2007年统计资料和文献查询获取的参数,估算了密云、房山氮养分输入、输出以及养分盈余,并分析了养分产生的环境效应.结果表明,2007年损失进入大气和水体环境中的养分总量分别为4 255.26 t和7 728.95 t,盈余在农田生态系统土壤中的养分总量分别为7 320.51t和14 566.64 t,通过损失途径进入环境和盈余在农田生态系统中的单位面积耕地氮养分负荷高风险地区集中在密云、房山的东部地区.通过对比研究.分析氮养分损失态和盈余态负荷基本趋势,找到了污染潜势产生原因.提出了促进农出氮平衡与降低氮养分负荷相应的调控对策和措施.

Nitrogen Nutrient Balance and Load in Agro-ecosystem of Miyun Fangshan County in Beijing

N nutrient is important indicators of soil fertility, then excessive N fertilization in intensive agricultural areas of China has resulted in serious environmental problems because of atmospheric, soil, and water enrichment with reactive N of agricultural origin. N nutrient balance and load in Agro-ecosystem of Miyun Fangshan County in Beijing were studied in this paper. Based on the theory of conservation of substance "input = output + surplus" in substance flow analysis (SFA )method, N nutrient balance model of agro-ecosystem was built. Data obtained from Miyun and Fangshan statistical report in 2007 and parameters acquired from recent references. Input, output and surplus of N nutrient in agro-ecosystem were estimated for appraising environmental effect. The result indicated: N loss enters in atmospheric and the water environment were 4 255.26 t and 7 728.95 t in 2007, N surplus were 7 320.51 t and 14 566.64 t in agro-ecosystem, and high environmental risk arose by these two county of N nutrient existing in east regions. Meanwhile, comparing the research between two area, the dynamic changing tendency of N loss and surplus was analyzed. The reason of the potential tendency of pollution was excessive N fertilization pactices , and the regulating ways relevant was given. A better N balance can be achieved without sacrificing crop yields but significantly reducing environmental risk by adopting optimum N fertilization techniques, controlling the primary N loss pathways, and improving the performance of the agricultural Extension Service.