Effects of soil internal forces on splash detachment and transport of aggregate fragments in Mollisols of Northeast China

Abstract

Soil internal forces can affect aggregate breakdown, and then impact splash detachment and transport of aggregate fragments. However, currently, the processes of soil splash detachment and transport under different soil internal forces are still not fully understood. Thus, to determine the effects of soil internal forces on the splash transport process, two soils (Binxian soil and Keshan soil) in the Mollisols (black soil) of Northeast China were selected to analyse the detachment and transport characteristics of aggregate fragments under different splash distances (0-10, 10-20, 20-30, 30-40 and 40-50 cm) through simulated rainfall experiments. Different concentrations of KCl electrolyte (from 1 to 10 À5 mol L À1 ) were employed as rainfall materials to regulate soil internal forces. The results revealed that the net pressure of soil internal forces and splash amount presented the same trend with decreasing electrolyte concentration, that is, increased initially (from 1 to 10 À2 mol L À1 ), followed by levelling off (from 10 À2 to 10 À5 mol L À1 ). The splash amount and net pressure had an exponential relationship (p < 0.01). Under the same electrolyte concentration, Binxian soil had a higher net pressure and splash amount than Keshan soil. The splash amount for the two soils was mostly distributed at a splash distance of 0-20 cm, and it exponentially decreased with increasing splash distance (p < 0.01). An empirical expression in our study was developed to predict the splash amount (M) based on the net pressure (N) and splash distance (S). The size distribution of splashed aggregates could be affected by the net pressure of soil internal forces, the greater the net pressure, the smaller size aggregates splashed. At each splash distance, the highest mass percentage was observed for the fragments <0.053 mm and accounted for 35.5% to 82.1% of the total splash amount. This study provides valuable information to better understand the processes and mechanisms of rainfall splash erosion in the Chinese Mollisol region.Ren-tian Ma and Weizhen Guo contributed equally to this work.