心土破砕機の利用拡張に関する研究 (第5報)

昭和35年度根釧試験地における調査結果 (1)

抄録

This paper reports results of the investigation which have been carried out in 1960 at TOKOTAN region in KONSFN, HOKKAIDO, to study on the lasting effects of pan-breaking for the first year after the treatment. In these plots, the pan-breaking was practised in last fall, and the results for the first period of the study, concerning to the physical properties of soil before and after the pan-breaking, were reported in Journal of the Society of Agricultural Machinery, Japan, Vol. 22, No. 3, 1960. The results in 1960 are as follows;
1. Pasture land
1) The peak resistance of the soil penetration appears itself at the depth of about 10cm below the soil surface. It may be able to guess that these peaks are caused by both the developed roots of grasses and the plane structure which has been formed by the freezing action of volcanic soil.
2) At both the untreated plots and the unaffected strips in the treated plots where subsoil has not been loosened by the pan-breaker, the peak resistances of the soil penetration are observed in their subsoils. It can be guessed that these peaks in the subsoil in dicate the hard pan which has been formed by the freezing action only. However, at the treated plots where subsoils were loosened, above mentioned hard pan has disappeared and not been regenerated during a year after the pan-breaking.
3) Roots of grasses in the treated plots are able to develop deeply than the untreated plots, and penetrate to the bottom of the loosened soil.
2. Crop field
1) Even in the treated plots, the hard pan which has been formed by the freezing action appears at the upper layer of the subsoil. However, the hard pan has been formed by traffic of tractor at the depth of 10-20cm below the soil surface.
2) The lasting effects upon the subsoil which has been loosened are observed evidently for the first year after the pan-breaking.