Pedologist

The ESR-signal intensity of fine quartz in the silt fraction, and the clay mineral composition were examined, in order to investigate the influence of eolian dust on the parent materials in two fine-textured soils developed on the Plestocene plateaus in the western part of Shizuoka Prefecture, Central Japan. The results were summarized as follows: The eolian dust brought with the winter NW-monsoon from the Precambrian area in the northern part of Asia Continent during the MIS2 (24-11 thousands years ago) in the Last Glacial Maximum was influenced severely on the parent materials in these soils, while the Pleistocence sediments which are autochthonous materials in the bed rocks of these soils were also influenced on their parent materials. Moreover, the Tephras such as Aira (A-Tn) were admixed into these soils.

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Paddy soils (166 points) in northern part of northeastern Japan were classified according to clay mineralogical composition. Smectitic and semi-smectitic paddy soils were dominant in Tsugaru Plain, western part of Aomori Prefecture. Amorphic volcanic ash soils were widely distributed in Sanbongihara terrace, eastern part of Aomori Prefecture. Smectitic and semi-smectitic paddy soils were observed in valley bottom lowland of rivers between Sanbongihara terrace. In Iwate Prefecture, paddy soils were diverse in clay mineralogical composition type in river terraces of Kitakami River (mixed type, smectitic etc.). Mixed type and semi-smectitic paddy soils were observed in alluvial lands of Kitakami River. Amorphic volcanic ash soils were distributed in northern part of Iwate Prefecture. In Akita Prefecture, semi-smectitic and chloritic paddy soils were observed in alluvial lowlands of Yoneshiro River. Smectitic paddy soils were observed in Hachirogata reclaimed land. Paddy soils were diverse in clay mineralogical composition type in Yokote basin (mixed type, chloritic, smectitic and dominant in 2:1-2:1:1 intergraded minerals). Tertiary sedimentary rocks or tuffs were distributed in upper reaches of many alluvial paddy soils, which contain substantial amount of smectites.

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Three sites located in Tokachi district, Hokkaido, Japan, were selected in this study. Soils of these sites were classified as Low-humic Andosols, Cumulic Andosols and Haplic Brown Lowland soils. From each site, one pair of cultivated upland soil and adjacent uncultivated virgin soil was selected to investigate differences in soil profile morphology, soil physico-chemical properties, and thickness of layer induced by cultivation and soil management among the soils in each site. (1) From the comparison of soil profile morphology of virgin and upland soils in each site, movement or loss of soil mass by cultivation and soil compaction by heavy machinery were observed. (2) Solid ratio and bulk density of the soil core samples increased and total carbon contents of the bulk soil samples decreased by cultivation and soil management in the cultivated upland soils. These results suggested that the cultivated soils were affected by soil management particularly by the use of heavy machinery resulting in soil compaction and increased soil disturbance resulting in the decrease in the soil organic matter content. (3) Judging from the differences in the soil profile morphology and soil physico-chemical properties, and statistical comparisons of phosphate absorption coefficient between the upland and virgin soils in each site, the thickness of layer in the cultivated soil profiles at each site was about 20-45cm thinner than that of the adjacent uncultivated soil profiles.

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The ESR-signal intensity of fine quartz in the silt fraction and the clay mineral composition were examined, in order to investigate the influence of eolian dust on the parent materials in a fine-textured soil developed on the Pleistocene plateau in the northern foot of Mt. Sarukura (354m), Sarukura Ohsawano, Toyama city. The results are summarized as follows: It was considered that the eolian dust brought with the winter NW-monsoon from the Precambrian area in the northern part of Asia continent during the M1S2 (24-11thousand years ago) in the Last Glacial Maximum was influenced severely on the parent materials in this soil. The autochitonous Pleiocene rocks were also considered to be influenced slightly on the parent materials in this soil. Moreover, a small amount of the tephras such as "AiraTn" was admixed with in this soil.

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