On-site soil dislocation and localized CNP degradation: the real erosion risk faced by sloped cropland in northeastern China

•Soil and nutrient redistribution caused localized land degradation.•The SOC and TN were halved on the sloped cropland compared to the nearby tree rows.•Atomic ratios of C:N:P differed as the slope curvatures diverted.•Minor geomorphic features govern localized biochemical cycling of major nutrients.•Topography-specific conservation practices must be integrated to local land use policy.