土壌構造に関する研究(第2報) : 日野土壌の物理的性質に就いて

抄録

In this paper the authors studied the differences in chemical and physical properties of the Hino-soils (Shiga prefecture). These soils were from various fields as crop plant field planted with or without perennial grasses (Leguminous and Others) and uncultivated field. By chemical methods, pH, CaCO_3,exchange acidity, exchangeable calcium, C/N ratio, iso-electric point, sedimentation volume in water amount of soluble aluminum, humus of various types, effects of drying soil on the amount of ammonium, were determined, and by physical methods, volume weight, porosity, aggregate factor, limit of plasticity, max. moisture capacity, with these soils. The results were summarized as follows : 1) Chemical properties (Table 1〜5) : The most characteristic difference was found between the top-soil (2nd-layer) of the field with grass and that (1st-layer) of the field without grass : that is, in the former CaCO_3 evidently remained much, but in the latter CaCO_3 was leached out, base exchange properties and types of humus were better in the former than in the latter and drying effects on the amount of ammonium were less in the former than in the latter. From these results, the top-soil (2nd-layer) of the field with grass was alike to the soil of the chernozem type, and the chemical properties of this layer were better than the top-soil (1st-layer) of the field with grass and also that (1st layer) of the field without grass. 2) Physical properties (Table 6,7) : of the top-soil (2nd-layer) of the field with grass the aggregate factor was 64.6 and the max. moisture capacity (mass) was 38.2 : this layer contsituted the good aggregated structure, and its colloid was thought to be changed qualitatively. Of the top-soil (1st-layer) of the field with grass the aggregate factor was 37.7 and the max. moisture capacity (mass) was 31.3; its aggregated structure was broken down and connverted into the single grain structure owing to the reason that the soil was not long disturbed by the ploughing while the field was planted with grass. Of the field without grass, the aggregate factor was 39.1 and the max. moisture capacity (mass) was 30.0; its aggregated structure was broken down, and its physical properties were changed to be unexpectedly bad. The top-soil (2nd-layer) of the uncultivated soil constituted the fairly aggregated structure, though the chemical properties were bad. 3) By means of the method to cultivate the perennial grass on the field, where the soil structure had turned out bad, the structure were improved, and brought to have good chemical properties. From these facts, we could recognize the possibility to keep the field soil always in a young stage against the weathering action.