Effect of Weathering Intensity on Physical and Chemical Properties of Typical Benggang Profile in Granite Red Soil Area of Southeast Guangxi

[Objective] The weathering intensity of granite red soil profile is closely related to the formation of Benggang, which promotes the development and expansion of Benggang. Studying the mechanism of weathering intensity and physicochemical properties on Benggang can provide a theoretical basis for the scientific prevention and control of granite Benggang. [Methods] The typical Benggang profile of granite red soil areas was selected as the research object, the oxide content and physicochemical properties of different soil layers were measured, and the influence of weathering intensity on the physicochemical properties of granite red soil was analyzed. [Results] (1) The major element oxides in the soil profile were mainly composed of SiO2, Al2O3 and Fe2O3. The weathering crust of granite showed the process of desilication and iron-rich aluminization. The weathering intensity decreased with the increase in the depth of the soil profile, which was in the stage of high weathering. (2) The physical and chemical properties of the soil profile exhibited heterogeneous. The surface layer was characterized by high organic matter, cation exchange capacity, clay content and saturated hydraulic conductivity, with strong cohesiveness and water holding capacity; whereas the lower layer had high sand content, loose structure and strong water permeability. (3) The results of correlation and path analysis indicated that weathering intensity was positively correlated with non-capillary porosity, organic matter, cation exchange capacity, clay content, saturated hydraulic conductivity and boundary water content. Fe2O3 had the strongest comprehensive determinative ability for clay content, sand content and boundary water content. (4) The surface weathering intensity was high, with a high proportion of clay, strong water adsorption capacity, strong cementation between soil particles, and good soil stability. The lower layer had a low of weathering intensity, with low content of cementing materials and boundary water content, poor soil corrosion resistance. When the soil was exposed or subjected to water erosion, it easily collapsed, forming Benggang. [Conclusion] The weathering intensity of soil profile has an impact on the physicochemical properties, which is an important factor to promote the formation of Benggang.