PAM application method and electrolyte source effects on plot-scale runoff and erosion

Previous research has indicated that polyacrylamide (PAM) soil amendments can be effective in reducing runoff and soil erosion by reducing soil sealing and stabilizing soil structure. Furthermore, the application of a multivalent electrolyte (Ca++) in addition to PAM has been shown to further reduce runoff volume and sediment yield on some soils. A field study was conducted using simulated rainfall to test the effectiveness of the method of PAM application (dry or in solution) and the effectiveness of two sources of Ca++ electrolytes. Treatments using an application of a liquid PAM solution that was allowed to dry on the soil surface were the most effective in reducing total runoff (62% to 76% reduction compared to control) and total sediment yield (93% to 98% reduction compared to control). Spraying of PAM in solution was significantly more effective in controlling runoff and erosion than was the dry granular application for the rainfall events simulated in this study. The slope of regressing sediment yield rate on runoff rate was used as a measure of erodibility. Sprayed PAM treatments dramatically reduced erodibility compared to the control. Dry PAM application also reduced soil erodibility compared to the control, but not as dramatically as the sprayed PAM. For intense rainstorms on initially dry soil, we recommend using a sprayed application of PAM for the best erosion control. More research is needed to determine whether this holds true for less intense storms under different field conditions.