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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.
Taking Yixing City in southern Jiangsu Province as an example, the evolution of farmland soil nitrogen balance and its main influencing factors at county scale in rapid urbanization are revealed through the calculation of income and expenditure.The results show that, since 1985, And the decrease of organic fertilizer use, the total amount of nitrogen input in farmland of Yixing City decreased. The nitrogen surplus decreased from 131.7kg / hm2 in 1985 to 5.0kg / hm2 in 2008, and the income and expenditure tended to balance gradually. Reduce the accumulation of nitrogen in farmland ecosystem, and reduce the harm of non-point source pollution.However, the reduction of human and livestock excretion can reduce the surplus of farmland nitrogen to a certain extent, but increase the direct discharge to the water body, Consideration is not conducive to the improvement of regional water quality.