Regulation pathways of physical crusts on seasonal dynamics of soil detachment capacity under different ridging patterns

Abstract

Soil detachment capacity (D_c) is a critical factor in soil erosion, yet seasonal dynamics of crust soils and their impacts on D_c remain inadequately understood. To address this gap, seasonal dynamics of physical soil crusts (PSCs) and their spatiotemporal interactions with D_c were investigated using two experimental plots (10 m × 3 m) with longitudinal and contour ridging under natural conditions from May to September 2023. Herein, PSCs were further categorized into structural and sedimentary crusts, respectively. D_c was measured through hydraulic flume experiments with a fixed slope (5°) and constant flow discharge (10 L·min⁻¹). Results showed that contour ridging facilitated organic matter accumulation, increased surface roughness and increased crust thickness by 0.028 cm compared to longitudinal ridging. However, it also disrupted soil aggregate stability in structural soil crusts, resulting in a 5.5 % reduction in the geometric mean diameter (GMD) and an increase of 12.03 % in clay content. In contrast, longitudinal ridging improved shear strength (19.93 kPa) but exhibited a more pronounced particle sorting effect. Bulk density of crusts increased 6.89 % and decreased 5.22 % under contour ridging and longitudinal ridging, respectively. Silt was enriched in the crust layer under both ridging conditions. D_c decreased by an average of 78.57 % within the progression of crust development from May to September. Compared to longitudinal ridging, D_c of structural crusts and sedimentary crusts under contour ridging increased by 125.45 % and 69.75 %, respectively. Duration of crusts development controlled the evolution of D_c by regulating key parameters such as crusts thickness. Among these, Crust thickness and GMD emerged as crucial parameters to evaluate the soil properties in rill erodibility modeling. Contour ridging demonstrated the potential to mitigate soil erosion and water loss by promoting PSCs formation and intercepting sediment in furrow. Re-ridging was recommended during the initial stage of contour ridging, whereas soil and water conservation measures should be seasonally adapted under longitudinal ridging.