中文摘要：

以内蒙古乌梁素海流域为研究区,建立区域氮素流动模型,研究了2006年种-养系统中氮素的收支状况及其对区域环境的影响。研究结果表明,乌梁素海流域氮素投入主要来源于耕地系统,草地系统的投入量很少。耕地系统氮投入量大于支出量,氮素盈余4.03×104t,平均盈余85.0 kg.hm-2。草地系统氮投入量小于支出量,导致草地系统氮收支亏损,亏损额为593 t,平均亏损0.99 kg.hm-2。大量氮亏损是引起当地草场退化的主要原因。此外,该流域每年随地表径流进入地表水的氮总量达9.25×103t,给当地水环境带来了巨大压力。肥料施用是地表水最主要的氮素来源,因此,控制农业面源污染应是当地水环境控制和管理的重点。

英文摘要：

Nitrogen flow in farming is one of the most important factors affecting the human environment,especially water environment.A regional nitrogen flow model was established for analysis of nitrogen budget of the farming-feeding system in the Wuliangsuhai Lake watershed,Inner Mongolia Autonomous Region in 2006 and its influences on the local environment.Results indicate that input of nitrogen in the watershed mainly comes through the farmland system and only a little through the pasture system.In the former the input is much higher than its output,leaving a surplus of 4.03×104 t or 85.0 kg·hm-2,while in the latter the input is lower than the output,resulting in a deficit of 593 t or 0.99 kg·hm-2.The massive loss of nitrogen is a primary factor causing degradation of the local pastures.In addition,the surface runoff in the watershed brings as high as 9.25×103 t of nitrogen into the surface water every year,posing a great pressure on the local water environment.Fertilizer application in the farming system is the primary source of the nitrogen in the surface water.It is,therefore,recommended that the priority of the management of the local water environment should be laid on control of the agricultural non-point source pollution.