The illuviation of CaCO3 and the deposition of clay in cal-ustic Isohumisols

In order to understand the illuviation of CaCO₃ and the deposition of clay, we chose a plot of 700 m × 900 m in the Arid Agriculture Experimental Station (AAES) of Wu Chuan in Inner Mongolia of China to serve as the study area. The study area is located in the arid and semiarid region, CaCO₃ were widely exist in the soil profiles. 80 soil profiles were undertaken. We measured CaCO₃ contents and soil textures. The study indicates that soil CaCO₃ was mainly in sub-surface horizons. The range of CaCO₃ content was from 6.7 g kg^-1 (humus horizon) to 231.1 g kg^-1 (calcic horizon). The means of CaCO₃ contents varied in the order Bk >; C >; AB >; A, and there were same trend for clay fractions. The illuviation of CaCO₃ and the deposition of clay are concurrent and interactive. Usually, there is a higher clay fraction in the calcic horizon because of flocculation. Through the research, we can further study the association between CaCO₃ illuvation and clay deposition.