Soil organic carbon in small watershed terraces and association with physical properties

The organic carbon, physical properties, and their relationship in terrace soil from Huanghuadian watershed in Inner Mongolia, China, were determined in this study. The soil organic carbon concentrated at the surface. The physical properties showed variations with the soil depth. The soil organic carbon contents were significantly correlated with contents of water, clay, bulk density, and sand, while non-significant correlation with silt and nutrient. Path analysis showed that the clay content was the major influence factor on the variation of soil organic carbon. The clay can hold water, then promotes plant growth and thus increase soil organic carbon.