Abstract:The artificial simulation rain experiment in field was designed to study the influence mechanism of polyacrylamide (PAM) on the process of runoff and sediment in four typical red soil slopes derived from different soil parent materials of South China under the condition of 140mm/h shortduration heavy rainfall. The experimental treatments included two kinds of PAM application rate of 2g/m2 and 10g/m2, which were expressed as PAM1200-2 and PAM1200-10, respectively. The results showed that the total runoff, unit sampling time runoff coefficient, cumulative sampling time runoff coefficient in each slope were increased significantly (p<0.01)， and the runoff with elevation order was quaternary red soil slope, red sandstone red soil slope, purple soil slope and granite red soil slope. The increase efficiency of runoff in the treatment of PAM1200-10 was more than that in PAM1200-2 treatment in different soil slopes except granite red soil slope. The increasing order of steady flow time was quaternary red soil slope (12min), red sandstone red soil slope (15min), granite red soil slope (24min) and purple soil slope (24min). There was no significant difference between the two kinds of PAM application rate (PAM1200-2 and PAM1200-10) in raising runoff yield. There was a significant decrease (p<0.01) in the total sediment, unit sampling time sediment concentration and unit sampling time sediment of each slope, the sediment reduction rate was the most remarkable in quaternary red soil slope with both of the two kinds of PAM application rate, there was slight difference in sediment reduction in red soil slopes derived from other three types of parent materials. The sediment reduction rate of PAM1200-10 was greater than that of PAM 1200-2 in different soil slopes, except purple soil slope. Among them, the sediment reduction rate of PAM1200-2 was more volatile than that of PAM1200-10. The sediment reduction rate of PAM1200-10 was relatively stable except the purple soil slope. In granite red soil slope, the effect of the sediment reduction of PAM1200-10 was significantly improved than that of PAM1200-2 (p<0.01).
