Abstract
Many erodible and unstable bare soil slopes were exposed under rainfall during the tidal flat reclaimed to be farmland in the coastal provinces of China. There is an urgent need for erosion control methods that are not only efficient and effective long term but also economical and environmentally friendly for slopes with saline-sodic soils. A combination of rock fragment cover (RC) and polyacrylamide (PAM) might be a potential choice. We investigated the synergistic effect of RC and PAM amendment rates on infiltration, runoff, and erosion processes for slopes of 15° with saline-sodic soils that were subjected to two 60-min simulated rainstorms with an intensity of 60 mm/ h under laboratory conditions. Nine treatments with three RC (0%, 15%, and 30%) and three PAM applied rates (0, 0.4, and 1.0 g/kg) in the upper soil layer were all exposed to two sequential rains of deionized water, and these two rainfall events (E1 and E2) were 4 h apart. The results showed that the embedded rock fragment cover decreased the infiltration rate (IR) and increased the runoff rate, which increased sediment yield rate (Rs) in rainfall E1. In E2, RC had a significant (P < 0.05) negative impact on the sediments yield rate by blocking the runoff in the rill. The PAM amendment significantly (P < 0.05) increased the IRs for both rainfall erosion processes, but the IRs were reduced with the PAM application rates increasing from 0.4 to 1.0 g/kg. PAM significantly (P < 0.05) decreased the soil loss in E1 and E2. The positive effect of RC on mean Rs in E1 was restrained as the PAM application rates increasing to 1.0 g/kg. An application rate of 0.4 g/kg was recommended for improving infiltration and controlling erosion because the increased infiltrated water could dissolve soil salt and transport it to drainage ditch though the underground pipes. The optimized combination formula had a PAM application rate of 0.4 g/kg and RC of 15% after taking the two sequential rainfall events into account.
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