Abstract
The soil behavior of grazing grassland was investigated from 1973 to 1980 in Shikoku Karst mountain area. The grazing grassland was developed using an unplowed method in August, 1973. In this paper, annual changes in soil dry density in situ (ρd: Mg/m3) are discussed as the typical property representing the soil behavior. The results obtained are summarized as follows.
1) ρd increased during the grazing season. A positive correlation is recognized between the amount of the increase and the population of grazing stock in case of surface soil. In the beginning of the grazing period (1974, 1975), the cattle hoofs seem to remarkably influence the surface soil causing an increase in its dry density.
2) On account of the freezing and thawing action, the soil became loose and a decrease in ρd occurred in spring. The amount of this decrease is nearly directly proportional to the freezing index. And it shows an annual reduction with an accumulation of the compaction effect as a result of the cattle hoofs. In the first winter season just after the development into grassland, grasses such as mischanthustype with a height of about 1 meter had been removed and the sowed grasses grew insufficiently. Because of such a change in the ground surfacecondition covered uithgrasses, it seem to reeluce the dry dencity remarkably.
3) It was thus found that the ρd of the grazing grassland changed cyclically. It seems to be due to grazing (increase) and the freezing and thawing action (decrease). And it was found that the compaction effect by the cattle hoofs accumulated in the soil and brought about a slight increase in the soil dry density on the surface soil, annually.
