香溪河流域坡耕地人工降雨条件下土壤氮素流失特征

Soil Nitrogen Loss From Sloping Farmland Under Artificial Rainfall in Xiangxi River Valley

采用人工模拟降雨条件下径流小区原位监测试验方法,对香溪河流域高风险输出源类黄棕壤坡耕地氮素随不同径流形式和泥沙的流失特征进行研究。结果显示,地表径流和壤中流的径流特征存在明显差异,次暴雨径流过程中,地表径流量约占总径流的68.44%,壤中流为31.56%。总氮、溶解态氮、NO3--N和NH4+-N的径流流失量分别为1.869、1.524、1.404和0.018 kg.hm-2,壤中流流失总氮、溶解态氮、NO3--N的贡献率均在70%以上;地表径流氮素流失以颗粒态为主,壤中流以溶解态为主。次暴雨径流过程中氮素总流失量为2.90 kg.hm-2,其中地表径流水相氮素流失量占14.56%,泥沙吸附态流失量占35.51%,壤中流流失量占49.93%。提高土壤的保肥蓄水能力,控制壤中流养分流失,对非点源污染控制具有重要作用。

In-situ monitoring of runoff under artificial rainfall was performed in a runoff experimental field located at the Xiangxi River Valley to investigate characteristics of nitrogen loss with different patterns of runoff and soil loss in a sloping farmland of typical yellow-brown earth, which is highly susceptible to soil erosion. Results show that surface runoff differed sharply from interflow. During a storm event surface runoff accounted for 68.44% of the total runoff and interflow for 31.56%. The loss of TN, DN, NO3--N and NH4＋ -N with runoff was 1. 869, 1. 524, 1. 404 and 0. 018 kg ~ hm-~, re- spectively. All the forms of N, except NH4 -N, were lost with interflows, which contributed over 70%. The N lost with surface runoff was mainly interflow particulate N, while that with soluble TN. The total loss of total nitrogen with runoff during the rainstorm reached 2.90 kg · hm-2 of which 14. 56% was lost with the water in surface runoff, 35.51% with the silt in surface runoff and 49.93% with interflow. Therefore, it is critical to adopt cultivation practices that are capable of raising the soil capacity of holding water and nutrients and controlling nutrient losses with interflow in management of non- point source pollution.