Abstract
In this paper anthers investigated on colloid-chemical properties of field soils in Mikatagahara (Shizuoka). The results obtained are summarized as follows : 1. Electrophoretic velocity (u) of soil colloids from sub soil increase simply with the change of pH value, and the amounts of soluble aluminium from this soil increase remarkably in acidic solution, pH of which becomes smaller than 4.0. 2. Soil colloids of uncultivated soils have a mininum value of electrophoretic velocity at pH 5.8 ; and the same tendency of aluminium solubility is observed in top soils as well as in sub soils. 3. Soil colloids of well cultivated top soils have remarkable minimum point at pH 5.8 on the pH-u curve ; and amount of soluble aluminium is very small even at pH 3.6. These results indicate the cultivated top soils maintain stable equilibrium against the change of pH in natural environment ; and monotonous pH-u curve of sub soil indicate that the soil colloids are not stable against the change of pH and they have tendency of being hydrolyzed by derease of pH.
