中文摘要：

采用室内人工降雨模拟试验的方法，研究了不同土壤前期含水量对壤土和砂黄土的坡面土壤硝态氮和磷素流失过程的影响．研究结果表明，淋失是土壤硝态氮流失的主要途径，仅在前期含水量高于20％时，才产生硝态氮大量径流流失；随着土壤前期含水量的提高，填土溶解态磷（DP）流失量与泥沙浸提态磷（SEP）流失量的比值呈减少趋势，砂黄土中该比值却呈指数函数增大趋势；2种土壤坡面径流SEP流失量与产沙量呈线性关系；通过坡面物质流失量（N03-N、SEP、DP和产沙量）与前期土壤含水量的二次多项式关系，获得了使黄土坡面物质流失量最小的最优前期含水量值，其中壤土为10．21％～11．37％，砂黄土为8．97％～13．39％．

英文摘要：

Antecedent moisture content is one of the important factors affecting runoff, as well as sediment and nutrient losses from slope-land. In this work, the effects of the antecedent moisture contents of the soil on the loss of Nitrate-N and phosphorus from the slope-land were investigated through indoor artificial rainfall experiments. The results show that NO3^- -N leaching plays a key role in the NO3^- -N loss of the soil, and the NO3^- -N in the soil transports into surface runoff when the antecedent soil moisture exceeds 20%. The ratio of dissolved phosphorus （DP） loss to sediment extractable phosphorus （SEP） loss decreases for the clay loam soil as the antecedent moisture increases, but increases exponentially for sandy soil. The amount of SEP loss was significantly positively correlated with sediment yield,and the relationships among the losses of NO3^- -N, SEP, DP and sediment losses and antecedent moisture contents may be described by a quadratic equation. In addition, the optimal antecedent moisture contents corresponding to the least losses of the nutrients were estimated based on the quadratic equation, and the optimal antecedent water content was 10.21% - 11.37% for clay loam soil and 8.97% -13.39% for sandy soil.