快速城市化背景下县域尺度农田氮素平衡状况的演变 ——以江苏省宜兴市为例

以苏南宜兴市为例,通过收支计算,揭示快速城市化背景下县域尺度农田土壤氮素平衡的演变及其主要影响因素.结果表明,自1985年以来,由于化肥施用量的大幅度下降和有机肥使用的减少,宜兴市农田氮素输入总量减少,氮素盈余由1985年的131.7kg/hm2减少至2008年的5.0kg/hm2,收支逐渐趋于平衡.这一变化有利于减少农田生态系统氮素的积累,从而降低非点源污染的危害.然而,人畜排泄物利用的减少虽然能够在一定程度上降低农田氮素的盈余,但增加了向水体的直接排放,从全局考虑不利于区域水环境质量的改善.

County-level changes in nitrogen budgets in agroecosystems against the background of rapid urbanization: A case study of Yixing Municipality in Eastern China's Jiangsu Province

Nitrogen budgets in agroecosystems in the year 1985,2003 and 2008 were calculated for Yixing Municipality in Eastern China's Jiangsu Province.Nitrogen surpluses on farmland was as high as 131.7 kg/hm2 in 1985,but had dropped sharply in recent years.By 2008,it had reached a well balanced nitrogen supply due to a remarkably lower input and the surplus was only a 5.0 kg/hm2.Reduced application of chemical fertilizers was the main explanation for the decreasing nitrogen input.Another major reason for the lower ...