Japanese Journal of Soil Science and Plant Nutrition

In this paper the following subjects are given, the materials being taken chiefly from those of North-East India. 1. The general questions on the acidity and liming of tea soils. 2. The result of the experiment with heavy dressing of lime at Tocklai Experiment Station (Middle-Assam). 3. The necessity of liming for highly acid soils and for exceedingly plastic ones, asserted by the scientific workers at Tocklai. 4. The methods of adjusting and maintaining the soil acidity with acid-increasing and acid-decreasing nitrogenous fertilizers, recommended by the scientific workers at Tocklai. 5. The brief summary of the above-mentioned subjects. It seems to the present writer that the unfavourable effect of liming, even with a smaller dose, for the alluvial sandy soils of Assam is due to the comparatively low acidity of the original soils, and to the decreasing of acidity during dry season owing to the accumulation of bases from underground. The conditions are quite different from those of the majority of our tea soils, where the leaching of bases is predominating. In Assam there are great many cases, where the increasing of soil acidity is necessary, but in Japan the opposite cases are rather common. The adjustment and maintenance of soil acidity, recommended by the scientific workers at Tocklai give us the valuable suggestions for the rational treatment of our tea soils.

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The present paper deals with the experiment concerning the speed of digestion and the existence of loss of nitrogen by long digestion in Kjeldahl method, on oil cakes and carbonized manure, with 13cc sulfuric acid and 4.5 grams potassium sulfate for 1 gram sample, using yellow mercuric oxide, copper sulfate or selenium as the catalyst. The results obtained are as follows : - The appropriate amount of mercuric oxide is 0.2 gram, copper sulfate 0.5 gram and selenium 0.05 gram as the catalyst for each 1 gram sample. The digestion with mercuric oxide is complete in 45-60 minutes, with copper sulfate in 120-140 minutes and with selenium in 80-100 minutes, while permitting 1/100 error as to the standard, the digestion with copper sulfate and that with selenium is complete in about 60 minutes. According to the above results, as A. L. PRINCE and others reported, selenium has no advantage over mercuric oxide in saving time in the digestion for determination of nitrogen in fertilizers. Using selenium much less than 0.05 gram, the period of digestion becomes longer than that above mentioned, and if selenium is used more than this amount, the results is liable to become lower than that of the standard. Using the appropriate amount of these catalysts, and preventing the diminution of sulfuric acid and the bumping on long heating, it is observed that there is no danger of loss of nitrogen by this operation.

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1) With 70 kinds of fowl excrement obtained from several localities in Kagawa Prefecture the relation between the chemical composition and the market price was studied. The chemical constituents and the prices are tabulated as follows : [table]2) No relation was confirmed between the market price and the amount of nitrogen as well as that of phosphoric scid. The price for one kan of nitrogen was observed to be 2-3 yen.

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In this paper is dealt with the exchange capacity of soil colloidal clay (<1μФ) and the rate of its decomposition by HCl of 1.10 sp. gr., as related to the climatic soil types. The soils examined are : (1) Thirteen samples of three profiles in Manchuria. (a steppe-, a brown forest-, and a podzol soil) (2) Seven surface soils of different mother rock in North-Kyushu. (3) Nine surface soils of different mother rock in Okinawa island. (4) Three surface soils in humid tropics, -Hongkong, Johore in Malay and Colombo. The total exchange capacity was ascertained by leaching with slightly ammoniacal ammonium acetate solution (ca. N) and determining the absorbed nitrogen by distillation with MgO. The total exchange capacity is expressed as M.E. per 100 gram of dry colloidal clay. A weighed portion of colloidal clay was treated with HCl of 1.10 sp. gr. at room temperature and after standing over night, the residue was filtered off and washed. The other weighed portion was digested one hour with HCl of 1.1O sp. gr. at boiling temperature with reverted cooler, then the residue was filtered off and washed. The exchange capacity of these two residues was determined by ammonium acetate method. Both the average values of total exchange capacity and the reduction in exchange capacity of the acid-treated residues as percentage of the total, and also the silica-alumina ratio are recorded in table I. Table I. Average exchange capacity of colloidal clay and its percentage reduction by treatment with HCl. [table] From the data in table I the following summaries are given : 1) The exchange capacity of manchurian soil colloidal clay is extremely high and that of humid tropics is the lowest, and those of North-Kyushu and Okinawa island lie between them. 2) The exchange capacities of each soil colloidal clays are not much reduced by the action of hydrochloric acid at room temperature. 3) The exchange capacity of residue, boiled one hour with HCl.1.10 sp. gr., of manchurian soil colloidal clay is reduced to the highest degree, and that of humid tropics to the least degree. 4) The exchange capacity of residue itself, boiled with HCl, of manchurian soil colloidal clay is the greatest, and its magnitude is greater than that of total capacity of the tropics. 5) The presence of exchange complexes other than crystalline clay minerals, for example, , , mixed gels", appear to be responsible for a considerable portion of that of soil colloidal clay, and the proportion of mixed gels contented, is the highest in manchurian soil colloidal clay and the lowest in that of the humid tropics.

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