Efficacy of granular polyacrylamide on runoff, erosion and nitrogen loss at loess slope under rainfall simulation

The chemical control of runoff, sediment and nutrient losses is one of the main measures of soil and water conservation and ecological improvement. A simulation experiment was conducted to investigate the effects of polyacrylamide (PAM) application rates (0, 0.5, 1, 2 and 4 g/m2), rainfall intensities (30, 60 and 90 mm/h) and the applied positions (top, middle and bottom with application rate of 2 g/m2) on runoff, soil and total nitrogen (TN) losses at loess slope. Overall, the results showed that PAM application rate of 1–2 g/m2 reduced runoff compared with no application of PAM on runoff. PAM application rate of 4 g/m2 reduced sediment losses most, but it increased the amount of runoff and TN losses in runoff. The PAM application rate of 2 g/m2 reduced runoff and nitrogen losses significantly. Soil and TN losses in sediment of PAM application position of the middle slope were significantly (p < 0.05) smaller than that of other PAM application positions. Considering the runoff, sediment and TN losses, PAM application rate of 2 g/m2 on the middle slope was the most feasible and beneficial mode for PAM application in the loess region.