Millet cultivation mitigates soil erosion in sloping farmland by regulating near-soil surface traits
Abstract
Introduction Crop growth induces seasonal variations in the near-soil surface traits, including vegetation features, root systems, and soil properties. However, the influencing mechanisms of variations in the near-soil surface traits on soil erosion remain unclear in sloping farmland. Methods Rainfall simulation experiments with slope gradients of 5.24%, 8.75%, 17.63%, and 26.79% were carried out on bare soil control (CK) and millet cultivation plots at different growth stages. Near-soil surface traits such as soil bulk density (BD), aggregate mean weight diameter (MWD), soil cohesion (Coh), soil organic matter (SOM) content, soil crust thickness (CT), critical shear stress (τc), rill erodibility (Kr), root mass density (RMD), root surface area density (RSAD), root length density (RLD), plant height (PH), and leaf area index (LAI) were measured. Results The results indicate that time-dependent dynamics of the near-soil surface traits exhibited seasonal variations with weak to strong variability. The initial runoff generation time (TR) was gradually advanced with the slope gradient and was delayed with millet growth. The mean runoff rate (RR), sediment rate (SR), and infiltration rate (IR) ranged 0.32–0.92 L m−2 min−1, 0.64–6.16 g m−2 min−1, and 0.43–1.09 mm m−2 min−1, respectively, during the entire growing season in the millet cultivation plots. The runoff reduction benefits (RRB) and sediment reduction benefits (SRB) ranged from 4.16% to 64.79% and from 17.35% to 93.18%, respectively. The interaction effects of soil properties, root system, and vegetation features accounted for the variations in the total runoff volume of 76.76%, sediment yield of 82.61%, and total infiltration of 85.71%. The sediment yield decreased with the improvement of the soil properties and the development of the root system as exponential or linear relationships. Conclusion The results demonstrate seasonal variations in the near-soil surface traits induced by crop growth and provide reliable support for soil erosion control and sustainable development in cropland.