Regulation of soil physical environment and erosion characteristics of farmland by amendments in the black soil region of Northeast China

The unique climatic conditions of the Northeast China’s black soil region drive the annual alternation of multiple erosive forces, which damage soil structure. Humic acid (H), lignosulfonate (L), and polyacrylamide (P) are commonly used amendments. However, the mechanism by which amendments regulate erosion under the additive action of freeze-thaw, wind, and rain remains unclear. This study aimed to elucidate how H, L, and P regulate soil hydrothermal dynamics, structural stability, and erosion under compound erosion. Using a self-designed wind tunnel-rainfall simulator, we tested the effects of amendments on aggregate distribution, soil temperature (ST), liquid volumetric water content (LVWC), and sediment yield. The results showed that, compared with control (CK), H, L and P significantly increased the proportion of large and medium-sized aggregates and improved structural stability, thereby enhancing the upper limit of LVWC and ST. When the concentration of L and P increased to 2.0 %, the soil structure became more solid, and the ST fluctuation range decreased by 5.7 %–8.7 %. The cumulative sediment yields of the L and P were reduced by 30.3 % and 99.2 %, respectively, compared with CK. However, the application of H degraded soil physical environment and reduced soil stability as the dosage increased. Compared with the CK, the cumulative sediment yield increased by 28.5 %. Using principal component analysis, we compared the comprehensive improvement effects of different amendments and application rates, and determined that the 2.0 % concentration of P was optimal. These findings provide scientific support for erosion control in Northeast China’s black soil areas.