农田地表径流总磷流失特性

Characteristics of total phosphorus loss into surface runoff from farmland

为了阐明农田地表径流引起的磷流失的过程和特征,在上海市青浦区一试验田采用不同的施肥方式,通过模拟降雨试验研究地表径流不同阶段中总磷流失状况.结果表明,在降雨-径流-土壤系统中,随着稳定强降雨的持续,总磷在径流前期阶段迅速流失而后期阶段流失较慢,前者的流失强度约为后者的3倍;虽然径流前期总磷流失强度大,但由于其持续时间远小于后期阶段,故后期反而有更大的总磷流失量,约为前期的1.5倍.经计算总磷流失量与径流量相关性系数接近于1,可见二者相关性显著,总磷流失量受径流量影响较大.不同施肥方式下总磷流失状况不同,顺着径流方向施肥会使土壤中的磷素更易于流失,其径流中总磷的峰值浓度约为垂直径流方向施肥时的2.5倍.研究结果对有效控制农田磷流失及相应的水体面源污染具有重要的参考意义.

To characterize phosphorus loss in surface runoff from farmland,simulated rainfall experiments were performed in a test field in Qingpu District of Shanghai. Different methods of fertilization were implemented to study the total phosphorus loss at different stages of runoff. The results show that phosphorus loss was more in the early runoff stage than that in the late runoff stage with stable heavy rainfall,and loss rate of the former is almost three times than that of the latter. However,it takes a much longer time of the late runoff stage,so the mass of phosphorus loss will be large in the late runoff stage,whichis approximately 1. 5 times than that of the early run off stage. Moreover,the total mass of phosphorus loss has a notable correlation with runoff volume where the correlation coefficient is close to 1 by computation,so runoff volume has a great effect on the mass of phosphorus loss. On the other hand,different applications of fertilizer also affect the bulk of phosphorus loss. The soil phosphorus would be easier to lose if the direction of fertilizer application is parallel to the direction of surface runoff flow,compared to the perpendicular flow. The peak value of total phosphorus concentration in the former condition is almost 2. 5 times than that in the latter condition. The results provide a significant reference for the reduction of phosphorus loss and the corresponding non-point source water pollution.