山口県秋吉石灰岩台地の赤色土

抄録

This pepar deals with the morphological and chemical characteristics of the red soil developed on the limestone plateau of Akiyoshidai, Southwestern Honshu (see Tables 1 & 2). From the following features the writers have recognized the soil as a non-podzolic red soil. 1. The soil does not show any evidence of bleaching or fading in the lower part of the A horizon, and it gives a bright reddish brown color in the B_2 horizon. Textures are heavy clayey throughout the profile. 2. The soil is characterized by a strongly acid reaction and an extremely low base status throughout the profile. The degrees of base saturation in the upper horizons are less than 15 per cent, and that of the B_2 horizon is about 20 per cent. 3. Since exchange reactions {pH_u(w)-pH_u(s")}throughout the profile 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. 4. Silica alumina ratios of the colloidal clay fractions range 2.2 to 3.0,and silica sesquioxide ratios are about 1.8. The molecular ratios of the clay resembles those of the re〓oils of Northern Kyushu and South China. 5. The soil of Akiyoshidai closely resembles in many respects the red soils of South China and other parts of Japan.