Large scale reclamations intended for agricultural land use in the south Kitakami massif have exposed low fertility subsoils onto the land surface, causing difficulties in the subsequent use of the land. In order to characterize these subsoils of various geological origins four sites, representing Paleozoic slate, Mesozoic granite, Mesozoic tuff and Tertiary tuff, were chosen. Except for weathered granite, generally these subsoils are clayey, compact, and low in permeability. They are also naturally low in organic matter, acidic with low base status, and low in CEC and buffering capacity. Thus, liming brings about a sharp pH rise. Low activity crystalline clays, sush as kaolinite, chlorite and chloritized 2 : 1 type minerals, are predominant in their clay mineralogy. To find out a means to improve the soil condition, effect of manuring was studied in a pot experiment, using leaf mustard as a test crop. Manuring in combination with liming and fertilization exhibited not only a remarkable positive effect on the crop growth, but also an improvement of the microbiological environment of the soil. In the Tertiary tuff plot the crop failed, when no manure was applied, presumably due to a nitrite accumulation, for no nitrite-oxidizing bacteria was detectable. Manuring is definitely effective in improving both chemical and microbiological properties of the poor geological subsoils.
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