関東州内の Terra rossa に就て

抄録

The chief results are here summarised as follows : - 1. The authors described about the formation and the properties of Mediterranean terra rossa according to the literature to compare with Manchurian terra rossa. 2. The author described about the climate, topography, geology, structure of profiles, weathering of dolomitic lime-stone and the productivity of the terra rossa of Kuantung-Chou, South Manchuria. 3. The climatic conditions of the region are as follows : -[table]According to the above results, the Lang's rainfactor and the Mayer's N-S quotient are a little higher than those of Mediterranean region, but it is almost same to have an important factor of alteration of wet and dry seasons. 4. The mother rocks of the region consist of various dolomitic lime-stone of upper archaean or under cambrian period and the terra rossa occurs only on the various dolomitic limestone, not on other rocks. 5. The upper horizon (A) of profiles consists of clay-loam, loam or sandy loam with gravels and iron concretion, but the under horizon (B) consists of clay and rich in mineral colloids. The characteristics of upper horizon are less humus and its dull yellowish brown color, which originated during the process of soil formation through the natural weathering. The characteristics of under horizon are its strong water holding capacity and its color (from red-brown to brownish red or purple red) and do not exhibit the acid reaction not with standing unsaturation soil to the alkaline bases. 6. Anothers characteristics of the soil are its low value of molecular ratios of SiO_2/Al_2O_3 and SiO_2/R_2O_3,dissolved in strong HCl (specific gravity 1.15). The calculated molecular ratios are described by the author as follows : -[table]These show an approximate ratios as those of Mediterranean terra rossa. 7. These soils stained indigo blue by methylene blue and light redish brown by acid fuchsin. These soils absorbed 4.1-4.9 c. gms. of methylene blue and 0.35-1.05 c. gms. of acid fuchsin per gram of soil. This fact explains that the soil contains both positive and negative colloids. The quantity of aluminium extracted by Dr. Seki's method (boiled for 5 minutes with 10% of Na_2CO_3 solution) are very much than silica and the value of its molecular ratio are 0.3-0.6,which correspond to about 1/4 of those of strong HCl extract. According to the results, the authors assume that the main part of colloids are consisted of colloidal clay and less quantity of free aluminium, because the amount of silica occuring in 10% Na_2CO_3 solution seems insufficient to hold as a silicate combination. 8. The value of SiO_2/Al_2O_3 and SiO_2/R_2O_3 ratios of the products of weathered dolomitic limestone, dissolved in strong HCl, are almost same as those of the soil. 9. The authors assumes that the structure of the profiles, physico-chemical properties and the mode of formation of the soil are almost same to those of Mediterranean terra rossa. From these reason, these Manchurian soils are called by tbe authors as terra rossa. 10. These soils are poor in content of available nutrients, and have very high absorption power of nitrogen and phosphorous. According to the results of culture experiments by the authors, these soils have strong requires of available nutrients, especialy in phosphorous and nitrogen. In this soil, one part of the fertilizer applied will be converted into unavailable form.