日本火山灰土に関する研究 : 第2報熊本県黒石原台地の黄色型について

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This paper deals with the morphological, mechanical and chemical characteristics of the yellowish brown type of the Japanese volcanic ash soils found on the terrace land of Kuroishibara, Central Kyushu. 1. The soil is characterized by a thick, dark surface horizon followed by a yellowish brown subsoil, and has a slightly well-developed profile. The soil is clayey in texture, and the humus content amounts to about 30 par cent in the upper-most horizon. 2. The soil is characterized by a strongly acid reaction and an extremely low base status throughout the profile. The degrees of base saturation are less than 8 per cent. Since the exchange reactions of the electrodialyzed materials [pH_u(w)-pH_u(s'')] indicate the exchange neutrality or alkalinity, the fundamental weathering process of the soil may be considered the anionic solvation and eluviation, and consequently, it is not a product of podzolization. 3. A considerable amount of free silica and free alumina is found in the soil. Silica-alumina and silica-sesquioxide ratios of the colloidal clay fractions are less than 2,and in particular, those of upper-most horizon are less than 1. The clay may be suballitic or allitic in composition. This fact may be attributed to the original compositions of the fresh ashes with the low molecular ratios, and to the intensive leaching process of bases and silica.
社団法人日本土壌肥料学会の論文
1952-11-10