Soybean yield in response to soil erosion under different dry and wet conditions

Soil erosion leads to reductions in soil thickness and fertility, threatening global agricultural productivity. However, the influence of different erosion degrees on crop yield under varying rainfall conditions remains unclear. This study collected 122 soil thickness samples across croplands of different grades to examine the relationship between black soil thickness and soybean yield. The observed soybean yield data (2011-2019) and simulated yields (1951-2019) using the ALMANAC model were used to assess the impact of soil thickness on yield under varying rainfall conditions. Results showed that the middle regions of hillslopes with the steepest gradients experienced the most severe erosion and had the thinnest black soil at 31.9 cm, whereas the bottom regions, as sediment deposition areas, had the thickest black soil at 47.8 cm. Contour tillage effectively reduced erosion, yielding soil thickness 1.5 and 1.3 times greater than those under up-and downslope and cross-slope tillage areas. A significant linear relationship existed between soybean yield and black soil thickness, with a 10 cm reduction in thickness corresponding to a yield decrease of approximately 8.0%. Climate change increase the risk of soybean yield reductions. Compared with typical years, extreme dry and wet years resulted in yield reductions of 14.3% and 5.0%. Thick black soil presented the highest soybean yield in normal and dry years, followed by medium black soil and thin black soil, but this trend was reversed during wet years. The higher clay and lower sand content in thick black soil improved water retention under dry conditions but increased the risk of waterlogging during wet conditions. In contrast, soil erosion led to thinner black soils with higher sand and lower clay content, which reduced waterlogging risk and resulted in higher yields under extreme wet conditions. These findings can contribute to improved land management and soybean production strategies.