Study on surface soil grain size and nutrient characteristics under different land use types

To investigate the effects of different land use types on surface soil texture and nutrient content, this study focused on four land use types (cropland, grassland, forestland, and bare land) in the agro-pastoral ecotone of Wuchuan County, Inner Mongolia, China. The mechanical composition and nutrient characteristics of the topsoil (0–2 cm) were analyzed. The results showed that the contents of silt, very fine particles, and fine particles in cropland, grassland, and forestland were significantly higher than those in bare land, while the contents of sand, coarse sand, and very coarse sand were markedly lower, indicating a general trend toward finer soil texture. Among the land types, forestland and grassland exhibited better sorting, whereas cropland and bare land had poorer sorting, with significant differences observed (P<0.05). In terms of nutrients, the organic carbon and total nitrogen contents in the surface soil of cropland, grassland, and forestland were significantly higher. Grassland showed a significant increase in total phosphorus content, while no significant changes were observed in forestland or cropland. For total potassium, grassland had significantly lower levels compared to bare land, while forestland and cropland showed no significant differences from bare land (P<0.05). Overall, the surface soil quality was ranked as follows: Grassland > forestland > cropland > bare land. These findings suggest that converting bare land to other land use types can effectively improve soil quality. Human agricultural activities and vegetation play a crucial role in enhancing surface soil quality in the agro-pastoral ecotone.