Variability in rill morphometry, surface runoff and erosion with soil conservation techniques (application of polyacrylamide and rice husk biochar and hydromulching) in deforested hillslopes under simulated rainfall

This study analyzed the effects of very intense rainfall (98 mm/h for 30 min) on soil left bare or treated with polyacrylamide, rice husk biochar and hydromulching. Rill morphometry, surface runoff and soil loss were measured in plots (100 cm × 50 cm) with three longitudinal slopes (10%, 17% and 28%). On the basis of these measurements, runoff and erosion were predicted via multiple linear equations for the experimental conditions. The effects of polyacrylamide application on surface runoff, soil loss and rill formation were not significant. In contrast, decreases in runoff generation and soil loss ((−40%)–55%) as well as rill widening and elongation ((−45%)–75%) were observed after the application of rice husk biochar and hydromulching. A multivariate statistical analysis revealed significant relationships among the soil hydrological, erosive and morphometric variables, as shown by coefficients of correlation greater than 0.78. Bare soils and plots treated with polyacrylamide on one side and those treated with rice husk biochar and hydromulching noticeably differ in their hydrological and morphological responses to intense rainfall. The multiple linear equations were accurate (R2 > 0.90) in predicting surface runoff and soil loss under all soil conditions. This study has several limitations (e.g., plot scale, simulated rainfall, and specific soil conditions). However, the results indicate the most suitable soil conservation techniques for specific rainfall intensities and conditions (excluding ecosystems subjected to deforestation). Moreover, this study provides multiple linear equations as hydrological tools to predict flood and erosion hazards in these areas.