Rainfall intensity and inflow rate effects on hillslope soil erosion in the Mollisol region of Northeast China

Soil erosion in the Mollisol region of Northeast China is increasingly severe and directly affects national food security and sustainable development. However, few attempts have been made to create a clear distinction between the effects of rainfall and inflow on hillslope soil erosion. A laboratory study was conducted to discuss the roles and contributions of rainfall intensity and inflow rate to hillslope soil erosion and to fit equations based on variations of rainfall intensity and inflow rate (RI + IR) for soil erosion. A soil pan (8 m long, 1.5 m wide and 0.6 m deep and with an adjustable slope gradient of 0A degrees-35A degrees) was subjected to designed rainfall intensities (0, 50 and 100 mm h(-1)) and inflow rates (0, 50 and 100 mm h(-1)). The results showed that the effects of RI + IR treatments on hillslope soil loss were significantly greater than those on runoff. Furthermore, the effect of rainfall intensity on hillslope soil loss was significantly greater than the effect of inflow rate. Under the same total water supply, an increase in rainfall intensity resulted in greater average soil loss rates and stronger fluctuations in soil loss than an increase in the inflow rate. The occurrence of rill erosion significantly increased sediment transport capacity on the hillslope, which resulted in an increase in soil loss. Utilizing rainfall intensity and inflow rate, runoff and soil loss equations were generated and validated, and the performances of the two equations were satisfactory. Furthermore, it was determined that both equations are most applicable to the prediction of hillslope soil erosion under long rolling hillslope conditions. For the Mollisol region of Northeast China, the key factor affecting soil erosion on hillslopes is soil particle dispersion caused by rainfall. Therefore, taking measures to cover the soil, such as corn straw mulching, would effectively reduce rainfall erosivity and have significant positive effects on soil erosion prevention and control.