Abstract
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.
