Effectiveness of Granular Polyacrylamide to Reduce Soil Erosion During Consecutive Rainstorms in a Calcic Regosol Exposed to Different Fire Conditions

Fire severity varies widely among and within wildfires. The objective of this work was to test the effectiveness of granular polyacrylamide (PAM) to reduce erosion in a Calcic Regosol exposed to different fire conditions. Three treatments were selected representing disturbances that coexist after a wildfire: unburned, low-moderate severity direct fire, and prolonged heating under moderate temperature [heated (HT)]. Granular PAM was spread on the surface of disturbed samples at two rates: (i) 0 (control) and (ii) 50 kg ha⁻¹. Additional application rates of 25 and 100 kg ha⁻¹ were tested in HT. Three 80-mm rainstorms were applied with an intensity of 47 mm h⁻¹, separated by drying periods. PAM reduced soil loss in all storms in unburned and direct fire, although runoff increased during the first storm due to increased runoff viscosity. In the highly stable HT, soil loss was reduced only with an application rate of 100 kg ha⁻¹ and after a drying period. In many cases, granular PAM could be effective to reduce post-fire erosion. In soils with high structural stability, a PAM dose should be selected to find a right balance between its stabilising effect on soil structure and its effect increasing runoff during the first storm.