表层土壤容重对黄土坡面养分随径流迁移的影响

Effect of Soil Bulk Density on Soil Nutrient in Runoff from Loess Slope

农田化学物质随地表径流迁移的问题,既是农业问题,又是水环境问题。地表土壤容重是影响土壤溶质随径流迁移的重要因素之一。通过室内模拟试验,研究了降雨条件下土壤容重对黄土区坡面土壤氮、磷和钾随径流迁移过程的影响。结果表明,随着土壤容重增大,初始产流时间提早,径流系数增大,土壤流失量增多,土壤磷和钾流失量也随之增大。径流养分浓度变化对土壤容重响应程度的大小次序是:NO3--N>PO43--P>K+。径流养分流失率过程曲线存在“峰值点”,它是土壤容重、溶质理化特性以及土壤水文参数综合作用的结果。通过数学模拟,进一步证实了幂函数是模拟黄土区非饱和水流条件下养分流失过程的最佳模型。本研究为深入理解黄土坡面径流溶质迁移机理提供了参考。

The release and transport of soil chemicals in surface runoff is not only an agricultural issue, but also a problem of the quality of surface and ground waters. Soil bulk density is one of the important factors affecting soil chemicals transportation with runoff. The characteristics of soil nitrogen, phosphorus and potassium transport with surface runoff on two types of soil from Loess Plateau were studied by simulating rainfall indoor. Results indicated that, when soil bulk density increased, the runoff initiation time shortened, runoff coefficient increased, soil erosion became heavy, and soil phosphorus and potassium loss increased. The sequence of extent of soil bulk density influencing on chemical concentration in runoff was NO3ˉ-N〉PO4^3- -〉K^＋. There was one peak during the chemical loss from runoff. The characteristics of peak, including time arrived peak to spend and quantity of peak value, was results from the synthetical interaction of soil bulk density, physical and chemical characteristics of chemicals and other hydrologic parameters. By simulating results, it was further confirmed that power function was the optimal model to fit the process of runoff chemical concentration under unsaturated condition and without rill erosion on the loess section. The study offered a reference for understanding the mechanism of soil nutrient in runoff transport of the loess slope.