Imogolite of Imogo-Layers in Kyushu

Abstract

A distinct, brownish yellow soil layer often intervenes between dark colored layers in the profiles of Ando soil in Kyushu, particularly in central east and southern Kyushu. The layer is called “imogo” in the Hitoyoshi district and “akahoya” in the Miyazaki district. The soil is characterized by a very low bulk density such as 0.4, and bears glassy particles in abundance, which are colorless and shard-shaped. It often displays exchange-neutrality or exchange-alkalinity. Plant roots are very few in the layer, and most roots are observed to make a bend along the layer surface, from perpendicular to horizontal. It seems that the plant root has trouble intruding the layer, probably because of its special structure (1, 2).