Studies on the Available Uses of Pan-breaker (X)

Abstract

This paper reports results of studies on the relations between the lasting effects of pan-breaking and the freezing action of soil, which were carried out on the 22nd-24th of March, 1961, at TOKOTAN region in Konsen, Hokkaido. In these plots, the pan-breaking was practised in the year before last (1959) and the last year (1960). The results are as follows;
1) Generally the depth of the frozen soil in the treated plots seems to be deeper than the depth in the untreated plots.
2) In the treated plots, the distribution of ice crystals in the frozen soil is comparatively sparse. While in the untreated plots, they are rich and the considerable parts of them appear themselves near the soil suface.
3) However, both in the treated and untreated plots, ice plates or pillars have been formed at the depth of about 5-15cm below the soil surface. Consequently, it can be thought that the hard pan will be formed just above and below the layer of ice pillars.
4) On the observation of ice distribution in the frozen soil, it became clear that, even in the treated plots, if the penetration was deep (depth 60cm) the permeability of rain water through the layer at 20-35cm depth was inferior to the shallow penetration (depth 30cm). In the double treated plots (60cm and 30cm depth), the permeability was adequate from the surface to the bottom.