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

Abstract

This paper reports results of the investigations which were carried out in 1961 at Tokotan region in Konsen, Hokkaido, to study on the lasting effects of pan-breaking. 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. Pasture land.
(1) The layer of which the soil resistance of penetration has come to 30-40kg exists at the depth of about 5-10cm below the soil surface. However the roots of grasses have developed in this layer. In and after summer, the hard pan of which the soil resistance of penetration has come to 50-60kg appeared itself just under the hard layer mentioned above. It may be able to guess that such a hard pan has been formed by the freezing action of the soil.
(2) In the treated plots where the pan-breaking was practised 2 years ago, roots of grasses have developed move deeply than in the untreated plots and penetrated through the bottom of the loosened soil. These distributions of roots show that the vertical development has continued stillmore for 2 years after the pan-breaking
(3) At the treated plots, mentioned above, the lasting effects in subsoil are able to be observed evidently near the penetrated traces of the chisels and standards. Especially at the upland, the soils which have filled up the passages of the chisels are very soft. However, at the lowland, the filled up soil has been compacted slightly, and the soil resistance of penetration has come to about 10kg.
2. Crop field.
(1) Even in the treated plots, the hard pan has been formed at the upper layer of the subsoil not only by the freezing action but also by traffic of tractor.
(2) The lasting effects upon the subsoil which has been loosened are observed evidently in the 2 nd year after the pan-breaking. Especially the soils which have filled up the passages of the chisels are very soft, and the soil resistances of penetration are only 0-10kg.