不同减量施肥条件下稻田田面水氮素动态变化及径流损失研究

采用过量施用化肥获得高产已成为近年来太湖地区的普遍现象，而由此引发的农业面源污染对水体生态环境恶化的贡献值也越来越大。通过对苕溪流域地区的田间试验，研究了8种不同减量施肥处理条件下，稻田田面水中氮素的动态变化特征和径流损失量，研究结果表明，（1）各处理铵氮浓度在施肥后迅速上升，1～3d达到最大值，而总氮在施肥后第1天便达到峰值，之后随时间变化逐渐下降，铵氮、总氮浓度在一周之后均降至较低水平。（2）田面水中铵氮／总氮比在施肥后3～7d达到峰值，之后逐渐下降。（3）田间任何1次的径流排水均会造成田面水氮素的流失，径流排水发生的时间与施肥时间间隔越小氮素的流失负荷就越大。（4）各减量化施肥处理年度累计流失负荷较常规施肥处理下降6％～53％，当季稻田氮素流失率在1．4％～2．6％之间。为减少农田氮肥使用量，降低氮素流失量，减缓农业面源污染提供理论依据。

Dynamics of nitrogen and runoff loss in ponding water of paddy field under different fertilization practices

Chemical fertilizers are intensively applied to agriculture in order to obtain high crop yield. However, the overuse of chemical fertilizers may cause agricultural non-point pollution. Therefore, in order to reduce N application and its runoff loss, this study investigated the dynamic changes of nitrogen and its runoff loss in pongding water of paddy field in Tiaoxi river catchment. The experiment consisted of eight treatments with different fertilizations and management practices. Our results showed that： （1） Application of N fertilizers sharply increased the concentrations of ammonia nitrogen （NH4~-N） and of total nitrogen （TN） in paddy ponding water. Their concentrations reached the peak in 1-3 days after fertilization and then descended to a low level in 7 days. （2） The ratio of NH4~-N/TN reached the maximum in 3 to 7 days after fertilization, and decreased later on. （3） The drainage from paddy field caused N loss, accounting for 1.4% and 2.6% of N applied. （4） The fertilizer reduction treatments decreased the N loss loading by 6%-53% as compared to the conventional treatment. This study provides some scientific knowledge and practical management for reducing the agricultural non-point pollution.