Abstract:The soil particle composition in 14 soil profiles(0-100 cm)of red soil hilly region’s farmland slope was analyzed in this study and combined with the related datas, such as soil erosion. The objectives were to clarify the spatial distribution characteristics of soil sand, soil silt and soil clay under the slope scale, and to reveal the migration law of soil partical composition in the vertical and horizontal directions under natural conditions. Results showed that under the slope scale sand, silt and clay exhibited moderate spatial heterogeneity, the variation coefficients were in the range of 17.6%-23.2%, 10.7%-18.8% and 13.5%-17.0%. The soil particle composition of 14 soil profiles(0-100 cm)in red soil hilly region was investigated along a slope. The spatial distribution of soil particle composition in both horizontal and vertical direction was analyzed combining with the related data, e.g. soil erosion. The objectives of the present study were to clarify the spatial distribution characteristics of soil sand, soil silt and soil clay under the slope scale, and to reveal the migration law of them in two directions under natural conditions. Results showed that sand, silt and clay contents exhibited moderate spatial heterogeneity, with coefficient of variation changing between 17.6% and 23.2%, 10.7% and 18.8%, 13.5% and 17.0%, respectively. Due to the deposition of coarse particles, higher sand content was observed in bottom slope than top and middle slope in both peanut and citrus orchard land (P< 0.05). The clay content in bottom slop was, however, significantly lower than other slop position (P< 0.05). Soil sand content decreased whereas the clay content increased with increasing soil depth (P < 0.05) for both vegetation types, mainly due to the movement of more clay particles with the infiltration process of soil water. The silt content did not change significantly in both horizontal and vertical directions. Sand content had stronger variation among slope positions and soil depths than silt and clay contents. In addition, the distribution of soil particles were also affected by vegetation types and cropping systems. The migration of soil sand along the slope was more significant in peanut land than in citrus orchard. The migration rate of clay in the vertical direction was stronger for citrus land than peanut land. However, vegetation types and cropping systems had little effects on the distribution of soil silt content.