Short-term effects of polyacrylamide application on soil detachment capacity in rills of deforested hillslopes: A flume experiment

Very few studies have explored the effectiveness of polyacrylamide (PAM) application on soil in mitigating rill erosion, especially in deforested environments. This study has measured the soil detachment capacity (Dc) on samples of deforested soil (untreated or treated with PAM). Dc has been estimated by flume experiments under three bed slopes (6.9 %, 17.2 %, and 18.2 %) and five flow discharges (0.078, 0.096, 0.116, 0.138, and 0.154 L·s−1) together with three key soil properties (cation exchange capacity, mean weight diameter of soil aggregates, and organic matter content). Compared to the untreated soil, Dc has significantly (p < 0.05) decreased on average by 38 % after the PAM application, while the cation exchange capacity, stability of soil aggregates, and organic matter content have increased (p < 0.001) by 50 % to over 100 %. However, Dc is weakly correlated to the latter soil properties (r < 0.33, p < 0.05). A clear discrimination between treated and untreated sites has been revealed by a multivariate statistical analysis. The soil erodibility parameter (Kr) and critical shear stress (τc) in rills have also been estimated through linear regressions on Dc for use in erosion models. Dc can be accurately estimated by linear equations using the stream power as a predictor (R2 > 0.77). Overall, the study has demonstrated that PAM is an effective soil amendment that reduces soil detachment in rills of deforested hillslopes by about 40 %.