中文摘要：

为了揭示农业面源污染的机理及其成因，选取我国南方典型灌区——湖北省漳河灌区，在野外试验结果分析的基础上，开展了农田排水氮素流失的影响因子及其规律研究．试验结果表明：降雨是影响农田排水中N流失量的最主要因素；作物叶面积指数等生理生态指标对N的流失起着非常关键的作用；节水灌溉对农田排水径流量和渗漏量有明显抑制作用；不同土地利用类型改变了植被和土壤水肥状况，影响N的流失；地形地貌会对降雨侵蚀量、降雨径流特征入渗和养分流失产生一定影响．

英文摘要：

On the basis of analysis of field experiments, the laws of nitrogen losses from agricultural fields are studied. In order to reveal the mechanisms and causes of agricultural non-point source pollution, the Zhanghe Irrigation District in Hubei Province, which is a typical irrigation district in south China, is selected to conduct experiment on the influencing factors and laws of nitrogen losses in the agricultural drainage water. The experimental results show that： rainfall is the most important factor influencing the losses of N from farmland; crop growing indexes such as leaf area index have a strong relationship with the losses of N; water-saving irrigation can decrease the runoff and percolation loadings in the drainage water; different land-use types change the losses of N; topography and landscape have impacts on soil erosion, rainfallrunoff characteristics and infiltration processes.