1965 Volume 26 Issue 4 Pages 249-254,235
This paper reports the conclusion of studies on the available uses of pan-breaker. The studies were conducted to find out the lasting effect of pan-breaking for 3 to 4 years at the three regions (East Hokkaido, Middle Hokkaido, and North Kyu-shu). Kind of soils are volcanic ash soil, clay loam soil and hard clay soil respectively.
The items of experiment are operating test, resistance of soil penetration, soil physical properties, and crop growth and yields. The troubles at each regions are reducing of crop yields by the soil freezing, the drainage, and soil compaction etc.
(1) The rate of operating. Two implements are trail behind 3 chisels (beet wings attatched) and rear mounted 1 chisel (no wings). The drawbar horse power of tractor are 80hp (crawler type) and 50hp (wheel type) respectively. The draft is 3.8 ton at the depth of 50cm, and operated area per hour is 35 to 45 ares at the speed of 0.7-0.8m/s.
(2) Soil penetration. The cone type penetrometer is a useful tool to sound the hardness of soil profile in field investigations. Equi-penetration curve is always used to find out the lasting effect. By the use of one square inch cone, the limited resistance is 40kg for crop root growth. The lasting effect of operating is three or more years at least. However, it is important things that the lasting effect will be reduced by the traffic of heavy duty implements.
(3) Soil physical properties. The looseness of soil can be compared by the apparent density and porosity. The apparent density at treated plot is 0.1-0.2 less than untreated plot. Porosity increases 5 to 10 per cent at the treated plot.
(4) Soil freezing. It has been resulted into the formation of plane structure, the soil errosion, and the reducing of fertility of soil. The profile of frozen soil is shown in Fig. 2 a, b. At the pasture land, ice pillars have been formed at the depth of 5 to 15cm below the soil surface. The hard pan at the crop field, ice crystals are found mainly at the lower layer in the frozen soil, and the amount of ice crystals are little by the double treatment (60cm and 30cm). At the pasture land, they are distributed to the over-all layers of the frozen soil and concentration of ice are little.
(5) Crop growth and yields. Any crops at the low swampy land did not grow before treatment, but considerable amount of sugar beets was yielded after the treatment. This is due to drainage effect. The height of dent corn is higher than untreated plots. The yields of potato and sugar beets at the deep treated plot are increased. At the hard clay soil, the yields of wheat is about two times of the rate at the untreated plot. Especially, the wheat above the subsoiling shows better cropping than the others.
