Soil nutrient redistribution in sloping farmland of dry–hot valleys in the upper Red River

Dry-hot valleys (DHVs) play a crucial role in plateau-specific agriculture in Southwest China. Sloping farmland, which constitutes the primary type of arable land in DHVs, frequently encounters severe soil erosion and nutrient depletion, significantly limiting crop yields. Despite this, there remains a lack of comprehensive scientific understanding regarding the impact of soil erosion on soil nutrient redistribution in DHVs slope farmlands. To address this research gap, we conducted a study in Yuanjiang DHV by selecting 12 sloping farmlands that employ traditional sloping tillage with corn as the main crop. We evaluated the distribution characteristics of soil organic matter (SOM), total nitrogen (TN), active phosphorus (AP), and active potassium (AK) at different slope positions (upper, middle, and lower) and soil layers (surface layer of 0–10 cm, middle layer of 10–20 cm, and bottom layer of 20–30 cm). Our findings indicated that the SOM, TN, AP, and AK contents in the lower slope are significantly higher than in the upper and middle slopes. This highlights the substantial influence of slope positions on soil nutrient redistribution. Using partial least squares (PLS) analysis, we observed varying degrees of influence of soil physical properties and pH on soil nutrient redistribution. TN exhibited the most pronounced response to slope position variations in slope on the sloping farmland in the Yuanjiang DHV. These findings suggest the crucial need for strategic planning and implementation of water-soil conservation measures in the DHVs to ensure sustainable and high-quality development of regional plateau agriculture, as traditional downslope farming significantly contributes to increased nutrient loss from the DHVs soils.