Effects of antecedent soil moisture on the variability of soil erodibility in red soil

Abstract

Soil erodibility, as an intrinsic soil property, reflects the susceptibility of soils to water erosion. Based on the sub-processes of soil erosion, soil erodibility can be divided into soil dispersibility and soil scourability, which are caused by rainfall and runoff, respectively. Both processes are strongly associated with soil moisture. However, few studies have investigated the effect of the antecedent soil moisture content on soil erodibility. In this study, a rainfall splash test was conducted under four different antecedent soil moisture conditions (dry, semi-dry, semi-wet and wet) and five rainfall intensities (40, 60, 80, 100 and 120 mm·h⁻¹) to investigate the impact of the antecedent soil moisture content on soil dispersibility, and a runoff scour test was conducted at four antecedent soil moisture contents and five flow discharges (20, 40, 60, 80 and 100 L·min⁻¹) to examine how soil scourability responds to varying soil moisture levels. Pedotransfer functions were developed to predict soil dispersibility and soil scourability. The results revealed that (1) the soil dispersibility reached the lowest values at an antecedent soil moisture content of 14.46%–15.68% when rainfall intensities were 100 and 120 mm·h⁻¹. However, the soil dispersibility did not change significantly when the rainfall intensity was ≤80 mm·h⁻¹, regardless of the antecedent soil moisture content. (2) The soil scourability decreased and then increased with increasing antecedent soil moisture content under all flow discharges. The lowest values were observed at the antecedent soil moisture content of 24.54%–27.98%. (3) Soil dispersibility/scourability could be predicted by the antecedent soil moisture content and rainfall intensity/flow discharge using pedotransfer functions, with adjusted R² values ranging from 0.479 to 0.775, respectively. This study quantified the relationship between soil moisture and soil dispersibility/scourability, providing a theoretical basis for predicting soil erosion processes. Future studies could investigate the mechanism by which soil moisture influences soil erodibility.