Effect of Raindrop Splashes on Topsoil Structure and Infiltration Characteristics

Raindrop splashing causes pore blockage in topsoil and reduces its infiltration capacity. In this study, simulated rainfall and infiltration tests were used to analyze the relationship between differences in the topsoil structure and the infiltration capacity of Lou soil on the Loess Plateau under different raindrop splashing conditions. The results show that, compared with soil existing under no raindrop splashing, the structure of the disturbed topsoil was altered, and the number of aggregates (A) and the three-dimensional fractal dimension (FD) degree were significantly increased (P < 0.05). At the same time, the pore volume (V-P) and macroporosity (P-L) were significantly reduced (P < 0.05). Aggregates splashed by 4.05 mm diameter raindrops were the most severely disturbed, and the pore clogging rate (CR) reached as high as 46.40%. After the broken aggregates blocked the pores, a dense and low permeable crust was formed on the topsoil, and it decreased the cumulative amount of infiltration and the infiltration rate. With increasing splash frequencies and raindrop diameters, the topsoil infiltration rate decreased gradually, and the soil infiltration reduction effect (IR) increased significantly. Three splashes later, the IR effect reached 94.21%. The study reveals the processes and mechanisms driving changes in soil infiltration characteristics from the perspective of changes in topsoil structure caused by raindrop splashing.