Clay mineral composition of Akahoya soils [in southern Japan]
1993
Nagatomo, Y. (Miyazaki Univ. (Japan). Faculty of Agriculture) | Tamai, M.
Clay mineral compositions of Akahoya soils collected from eighteen representative profiles in Kyushu and Tanegashima districts were investigated to know the relationship between the depth from the land surface and the clay mineralogical properties of Akahoya soils. Akahoya soils were divided into three types of group (Type I, Type II and Type III) by the depth from the land surface. The results obtained were as follows. 1) All Akahoya soils contained large amount of allophane-like material, allophane and imogolite and small amount of montmorillonite and montmorillonite (or vermiculite) chlorite intergrades. Very small amount of illite and kaolinite were present in most of Akahoya soils. Gibbsite was also found in some of the Type I Akahoya soils. 2) Large amount of halloysite was present in the A horizon of the Type II akahoya soils in which silicas especially accumulated. 3) Allophane and imogolite coexisted in all Akahoya soils. The degree of formation of imogolite and imogolite/allophane ratio decreased in the order of Type I Type II Type III with increasing ratio of SiO2/Al2O3. 4) Content of allophane-like material was greater than those of allophane and imogolite in a horizon of Akahoya soils which accumulated larger amount of organic matter, on the other hand content of allophane-like material was smaller than those of allophane an imogolite in B and C horizon of Akahoya soils
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