根据野外径流试验及对流失土壤、径流样品分析，研究了渭北坡地苹果园在径流作用下磷素的流失、坡面磷素的分布、径流过程的影响及泥沙与磷素流失的关系，得到以下结论： 1、径流中颗粒态磷、总磷与径流中泥沙含量有着密切的关系，径流中泥沙的含量与总磷及颗粒态磷有着显著的线性关系。随着径流强度的增加，径流中颗粒态磷、总磷的浓度随之增大；颗粒态磷是坡地果园磷素流失的主要方式，径流初期是磷素流失最严重的时段。 2、径流强度对溶解态磷浓度并没有明显的影响，只是随着径流过程的延续，溶解态磷浓度逐渐增加，但是幅度不大，与溶解态磷浓度比较小有关。径流强度的大小对颗粒态磷的浓度有影响，径流强度大，颗粒态磷浓度较高。 3、坡面上磷素浓度从坡顶到坡底呈现逐渐增加的趋势，其原因是上游径流流速小，侵蚀强度不大，下游形成了股流，侵蚀比较强烈，径流的携沙能力强，所以磷含量比较大。 4、土壤总磷的流失率（RLR）与距坡顶距离（d）有线性关系，其拟合方程为： RLR＝-0.0202d + 0.4723，（R2＝0.7336）。RLR与d存在着负相关关系，从坡顶到坡底，土壤总磷的流失有减弱的趋势。 5、总磷输出速率在径流最初阶段最大，其变化呈对数曲线分布，随着径流过程的延续，总磷的输出速率先期下降比较快，后期相对变化幅度不大。溶解态磷输出速率则呈现逐渐上升趋势，其变化趋势没有总磷那么明显。在磷素累计输出量变化中，径流前期增加速率较快，后期较平缓。

According to the analysis of the field experiments, drains doil and the runoff sample, this research was concentrated on the losing of Phosphorus, the distribution of Phosphorus on the sloping orchards, the influence of runoff and the relations between the silt and losing of Phosphorus on the apple sloping orchards around the north Wei River. It has been concluded in the following aspects. 1. It was demonstrated that in the runoff the capacity of silt and sand was closely connected with the concentration of total phosphorus (TP) and particular phosphorus (PP), And it has a linear relations between them. The more intensive the runoff was, the more quantity of the TP and PP increase, and the losing of PP was the majority form of Phosphorus losing in this area. It is the most important time that the Phosphorus losing, it has a very remarkable linear relations between the capacity of silt and the TP and dissolved phosphorus (DP). 2. The intensity of runoff was less obviously affecting the concentration of DP, it is just increasing on the runoff, and it is related with the slowing DP. But, the intensity of runoff was obviously affecting the density of DP and TP, the moe intensity of runoff, the more density of PP, the less intensity of runoff, the less density of DP. 3. The density of Phosphorus on the sloping was gradually increasing from the Upside of the slope to the Lower part of the slope. Because the rate upsid is small, and the intensity of corrosion is low. On the downside, it becoming the Stock class, and the intensity of corrosion is big, and the runoff carries the more silt. So, the content of Phosphorus is biger. 4. It has the linear relations between the losing rate of slope soil (RLR) and the distance from the valley to the peak (d), that the fitting equation was: RLR = -0.0202d + 0.4723, R2 = 0.7336, and its pertinence was really notable. The losing rate of slope soil (RLR) was minus realated with the distance from the valley to the peak (d), up the slope to down the slope, the losing of TP of the Soil was down. 5. Finally, the diversified curves of the cumulating output capacity between the total Phosphorus and dissolved Phosphorus were all logarithm distributed. By the increasing of the time of runoff, the output of TP is down more fast first, and then the change scope is slowly. But, the output of DP is gradually riseing, and it’s tendency is not obvious as the TP. On the accumulation output of Phosphorus, the rising rate of the beginning of runoff is faster, and on the end of the runof , it becomes slower.