Abstract
The particle-size fractionation followed by the densimetric fractionation using the bromoform-ethanol systems of ultrasonicated soil sample from A horizon of acidic volcanic ash soil, clay minerals of which was dominant in montmorillonite, was carried out, The silt-size complexes were dominant in amorphous matter and iron oxide. And the inorganic part of the clay-size complex was mainly consisted of montmorillonite, but small amount of amorphous matter and iron oxide. These results show the heterogeneity of the organo-mineral complexes in soils.
