Abstract: The aim of this research is to exploring the variation of soil disintegration rate with soil type and depth profile, as well as the regional heterogeneity of soil disintegration rate and its main impact factors in the upper and middle reaches of the Yangtze River. Hydrostatic disintegrating method was employed to test the disintegration rate of different types of soils and indoor physical and chemical analysis were carried out on the soil specimens. Results reveal that: the disintegration rate of sandy red soil is the largest, followed by sandy yellow soil, cinnamon soil, loam yellow soil, lime soil, purple soil, brown soil and loam red soil. The curves of disintegration rate variation along the vertical section can be classified into four types: descending, increasing,protruding and concave. The soil disintegration rate in the southern area of Shaanxi province and the mountainous and hilly areas in east Hunan and south Jiangxi are the highest, followed by the upper reaches of Jialing River, and the soil disintegration rate in Danjiangkou reservoir area, Three Gorges Reservoir area, Sichuan Basin and the Yunnan-Guizhou Plateau are relatively low. The water-stable aggregate content and organic content in weathered soil (>0.25 mm) are the main factors affecting the soil disintegration rate.

Key words: soil, disintegration rate, hydrostatic disintegrating method, regional heterogeneity, upper and middle reaches of Yangtze River