【摘要】 采用田间试验、定位监测和参与式农户调查等方法,研究了农林复合系统氮素平衡和非点源污染特征。结果表明,目前旱地和整个农田子系统氮素略有盈余,水稻田和复合系统有少量亏缺,林地亏缺较大。而20世纪60年代农田氮素严重亏缺,水土流失是产生亏缺的主要原因。模型评价表明,旱地和水稻田目前的氮素平衡基本合理,但化肥施用的剧增已导致农田气态氮素释放以及地表水和地下水非点源污染风险的增加。研究显示,林地极大地减轻了系统水土流失,促进了氮素在各系统间的合理分配。合理施肥、保护林地、实施水保耕作和完善养分管理政策体系是减少农业氮素非点源污染的重要途径。更多还原

【Abstract】 Field experiments; inspections and participatory rural appraisal were adapted to study on nitrogen balance and non- point source pollution in a typical agro- forestry ecosystem. The results showed that there was a little nitrogen surplus in croplands and in farming system; but a little deficit in paddies and in the catchments nowadays. In addition, the forest system showed more deficits. However, the recorder in 1960s showed a great N deficit mainly because of heavy erosion. The nitrogen balances of croplands and paddies were relatively reasonable by a mathematical appraisal model. Unfortunately, a great increase of N chemical fertilizer applications had already led to more non- point pollution risks of gas N emissions and - N concentration in water surface and groundwater. It has been clear that the forest was playing a great role in reducing erosion and improving the nitrogen distribution among different ecosystems. Logical fertilizer applications, forest protection, no- tillage farming and nutrient management policy were the important ways in reducing non- point resource pollutions of agricultural N.更多还原