Agricultural non-point source pollution is one of the main factors contaminating the environment. However, the impact of rainfall on loss of non-point nitrogen is far from well understood. Based on the artificial rainfall simulation experiments to monitor the loss of dissolved nitrogen (DN) in surface runoff and interflow of vegetable field, this study analyzed the effects of rainfall intensity and fertilization scheme on nitrogen (N) loss. The results indicated that fertilizer usage is the main factor affecting the nitrogen loss in surface runoff, while runoff and rainfall intensity play important roles in interflow nitrogen loss. The proportion of DN lost through the surface runoff was more than 91%, and it decreased with increasing rainfall intensity. There was a clear linear trend (r² > 0.96) between the amount of DN loss and runoff. Over 95% of DN was lost as nitrate nitrogen (NN), which was the major component of nitrogen loss. Compared with the conventional fertilization treatment (CF), the amount of nitrogen fertilizer applied in the optimized fertilization treatment (OF) decreased by 38.9%, and the loss of DN decreased by 28.4%, but root length, plant height and yield of pak choi increased by 6.3%, 2.7% and 5.6%, respectively. Our findings suggest that properly reducing the amount of nitrogen fertilizer can improve the utilization rate of nitrogen fertilizer but will not reduce the yield of pak choi. Controlling fertilizer usage and reducing runoff generation are important methods to reduce the DN loss in vegetable fields.

中文翻译：

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河北省模拟降雨试验下菜地氮素流失

农业面源污染是污染环境的主要因素之一。但是，降雨对非点状氮损失的影响尚不清楚。在人工降雨模拟试验的基础上，监​​测菜田地表径流和土壤间流中溶解氮（DN）的损失，分析了降雨强度和施肥方案对氮素损失的影响。结果表明，肥料用量是影响地表径流氮素流失的主要因素，径流和降雨强度在流际氮素流失中起着重要作用。通过地表径流损失的DN比例超过91％，并且随着降雨强度的增加而降低。有明显的线性趋势（r ²> 0.96）之间的DN损失和径流。硝酸盐氮（NN）损失了超过95％的DN，这是氮损失的主要组成部分。与常规施肥（CF）相比，优化施肥（OF）施氮肥减少了38.9％，DN损失减少了28.4％，但白菜根长，株高和产量却降低了。分别增长了6.3％，2.7％和5.6％。我们的发现表明，适当减少氮肥的用量可以提高氮肥的利用率，但不会降低白菜的产量。控制肥料的使用并减少径流的产生是减少菜地DN损失的重要方法。