The Black Forest Soils derived from andesitic volcanic ashes, are widely distributed on uplands, hills and mountains in Japan. They are characterized by a thick and black A horizon which is rich in humus. Though the former is not just the same as the latter, the Black Forest Soil closely resembles the Ando Soil, Black, which is recently named by some American pedologists, in many respects. Normal profiles of the soil in well-drained area consist of four or five horizons, and their, morphological characteristics observed are as follows : 1) A_0 layer (about 3〜5cm in thickness) Thin leaf litters with dark grayish brown organic substances partially decomposed. In grasslands, the layer is heavily matted with grass rootlets. 2) A_1 horizon (15〜40cm in thickness) Black or brownish black loam to silt loam, rich in humus. Very loose. soft and mellow in consistency, and floury feel between fingers. Fine granular structure weakly developed. Crumbs are very friable. 3) A_2 horizon (20〜50cm in thickness) It resembles the upper horizon in various respects, although the former is more compact and blackish than the latter. Loam to clay loam in texture and coarse or very coarse nuciform structure weakly to moderately developed. Lumps are very friable. The horizon gradually merges into the lower horizon and does not show any tendency of bleaching. In Onji type found in Eastern Kagoshima (in the vicinity of Kanoya City), a thin pumice layer occurs in the lower part of the A_2 horizon or in the upper part of the B_1 horizon. 4) B_1 horizon (15〜30cm in thickness) It is a transitional horizon. Dark brown loam to clay loam with some humus transported into the horizon from the upper part. Coarse or very coarse blocky structure moderately to strongly developed. Lumps are fine porous and friable. The boundary between the B_1 and the B_2 or B_2C horizons is somewhat wavy or tonguelike, though clearly defined. 5) B_2 or B_2C horizon The colours of the horizon, closely resembling those of the parent materials, range from very light yellowish brown to brown. It is obvious that colour by itself cannot be used as a criterion in soil classification, but when considered in connection with other morphological characteristics of the Black Forest Soils the difference in colour of the B_2 or the B_2C horizon is of extreme importance in the subdivision of the Black Forest Soils. Fine sandy loam to clay loam and moderately or strongly developed blocky structure. When dry, this horizon gives very coarse prismatic structure as usually seen in loessial regions. Lumps are very porous and friable. Compact and non plastic. In Onji type, the subsoil is saw-dust like in appearance. There are many minute fragments of glassy substances throughout profile. In Brown and Yellowish Brown types found in Kanto Plain, some small reddish brown lapilli occur in the B hofizon. From the results of the field observation carried out by the writer, it can hardly be doubted that the Black Forest Soils with developed profiles, as has already been stated by Thorp, are ABC soils, whereas their younger members belong to AC soils. In considering their morphological and chemical characteristics and origins, with considerable possibility we may say that the Black Forest Soils belong to one of the intrazonal soil types. Some of them have one or more buried profiles. Examples of these buried soils found in southern Kyushu are shown in Figures 1 and 2. According to the provisional classification based on their morphological characteristics and reactions, the Black Forest Soild as now recognized are classified into the following sub groups : 1) Onji type, 2) Brown type. 3) Light Yellowish Brown type, and 4) Yellowish Brown type. Main characteristics and distribution of these types are given in Table 5. Some Japanese pedologists have called them the Black Soils or the Prairie-like Brown Forest Soils. The Ando soils mean dark soils in Japanese language.

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In this study we have planned to investigate the influence of three manurial ingredients on silica contents of the rice plant, especially on silica-cell formation in leaves. Rice plants are water cultured with different concentration of NP, and K respectively as shown in Table 1. Plants thus cultured are used for the determination of ash- and silica-contents after harvest, and data are given in Table 3. And at the same time density of silica-cell at middle part of the last leaf of the main stem are measured microscopically at pre-earling stage. The results are given in Table 2. Judging from these date we obtained the following results. a) The higher the Nitrogen concentration of culture solution is, the lower are the silica content of ash and the density of silica-cell in the leaf. b) In the case of Phosphorus, there is the same tendency as in the case of Nitrogen. c) The silica content of ash and the density of silica-cell rise to a certain degree, with the increase in concentration of Potassium in the culture solution, and then it seems to maintain constant. d) The SiO_2 content of the plant is about 5% at normal condition. And it may be considered that SiO_2 in sol condition in the sap of the leaf-cell becomes unstable and precipitates itself in the form of silica-cell.

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In this paper the Authors investigated the manual value of Aluminium and Magnesium nitrides for rice plants and wheat plants by the pot experiment. These nitrides were produdced by heating the metal aluminium and magnesium wich nitrogengas in the silica glass tubing at 800〜1000℃. The results may be summarised as follows. Magnesium nitride and Aluminium nitride were observed to be less effective than sulphate of ammonia for rice plants aud wheat plants. Especially Aluminium nitride were not available for rice plants.

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Authors measured the ζ-Potential of the soil colloids in the following four states by the electro phoresis, using the normal and aged paddy soils. A) Soil colloid, made from the air dry soils. B) Soil colloid in the reductive state. C) Soil colloid in the unstable oxydative state. D) Soil colloid in the oxydative state. measured results are as follows. i) Every sample were negative colloids. ii) In B state electro phoretic velocity of the normal paddy soils are larger than that of the aged paddy soils, and Electrossmotic velocity of water against the glass the former become very small, but does not in later. iii) The Order of the electrophoretic velocity of every soils are As follbows. (C)>(A)>(D)>(B) iv) Ferrous ion were detected in the (B) state soil solutions, but in the (A)(C)(D)states.

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Of late, manganese has used as fertilizers. Both the volumetric and the gravimetric method of the determination of manganese in the separation of Mn and Fe need the double and triple precipitation. So we studied the method that mangane is measured polarographically with the separation of iron, and manganese in fertilizers was possible to estimate in 0.2 n KCN. This method is rapid in time and simple in process and accueate. 1) E.T. Vertier ; Anodic oxidation of Mn-tartratete and its analytical application. Collection, 11 (1939) 233. 2) E.T. Vertier ; The electrodeposition of Mn from Cyanide solutions, Collection, 11(1939), 216. On the determination of iron by polarograph, fluoride, mannitol, complex cyanides, thiocyanate, citric acid, tartaric acid, oxalic acid, etc. have been examined. And although oxalic acid is most ideal of all on the form of the wave, it precipitates calcium in phosphate rocks. On this point malonic acid COOHCH_2COOH does not precipitate it and the form of its wave is as ideal as oxalic acid. So malonic acid was examined on the determination of iron in phosphate rocks and a desirable result was brought. 5c.c. of the solution of a calculated phosphate rocks decomposed with aqua regia is brought into 25c.c measuring flask and diluted to the mark with 1 mol malonic acid-solution neutralized with KOH to pH ca. 5.0 and the cathodic wave from ferric complex to ferrous was measured polarographically in comparison with it of a known iron solution, the content of iron in phosphte rocks was determined directly. This method is rapid in time and simple in process and small in error in comparison with gravimteric or volumetric procedures. With small percentages of iron, the method is inherently accurate and also it is able to determine each of ferric and ferrous ion at the same time.

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In this papers the author investigated the change of chemical properties, above all the nitrogen fertility, in the maturing process of newly reclaimed soils, Mikatagahara Sizuokaken, under cultivation. The results are summerized as follows : (1) In the process of cultivation, the nitrogen fertility without reference to the period of cultivation. The type of comsuming process of nitrogen fertility is closely similar to the case of the soils, Koibuchimura Ibaragiken. (2) In the process of cultivation, and there is scarcely change in the amount of total nitorogen, but total carbon decreases gradually, and C/N ratio becomes near 10,that is the ratio of humus. (3) After reclamation the amount of exchangeable calcium increases, and acidity neutralized in proportion to the time of period in which the soil is cultivated.

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In the degrated paddy soils, the free iron oxides in the fallow soils were leached during the waterlodged periods, and were accumulated at the lower layers. In this paper the authors investigated the leaching mechanisms of the free iron oxides. The results are summerised as follows. In the reductive layers of the paddy soils, H_2S (S") are formed from the sulphates and organic substances which contain the sulpher, and F^<・・> are formed from the free iron oxides. In the case of the normal paddy soils F^<・・> predominate over S", But in the case of the degrated paddy soils S" predominate over F^<・・>, so that the formed FeS-gel change to the sol and then with the percolate-water the FeS-sol are leached from the fallow soils to the lower layers.

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The writer isolated and purified several humic acids from black soil and humus volcanic ash soil respectively. Some their properties were studied and the following results obtained. 1.In humus volcanic ash soil a kind of humic acid with high degree of black color tone exists, which is similar to grey humic acid isolated from black soil with respect to the action for alkali solution. 2.But this kind of humic acid seems to be diferent from grey humic one judging from its chemical composition, color degree and process of humification. For this reason the writer should like to give it the name of "Black humic acid".

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Colorimetric determination of Potassium with Na-Dipicrycaminate was performed by using the stufenphotometer. The principle of this determination is identical to Amdur's method. But the stufenphotomter was used in the place of electrophotometer. Therefore, the most convienent, condition for Stufenphotometry was investigated. The result was as follows (see fig 1. 2. 3.) ○The filter : - S 47 ○Thickness of solution : - about 20 mm ○Concentration of reagent : - O.3〜0.8% solution of Na-dipicrylaminate was suitable for the determination of 0.1〜0.9 mg K. ○Concentraton of solution for colorimetry : - 0.3cc of supernatant liquid of excess Na-dipicrylaminate soln/100cc of dislilled Water. The effects of foreign ions on this method were discribed below. Na, Ca, Mg does not interfere the determination of potassium with the exception of large amounts of them. Using 0.5mg K the author determind the potassium with accuracy of ±2.5% in the presence of 10mg Na, Ca, Mg (see Table 1 and 2) By this method the determinations of potassium in the plant tissues were made, and their errors were also within ±2.0% (see Table 3). This method can be applicable for the Duboscq colorimeter. The stufenphotometer reading (I/I_0×100) is substituted with the reading of Duboscq colorimeters scale which indicate the depth of 0.02% potassium bichromate solution when both halves of the field appear equally bright. The depth of Na-dipicrylaminate solution for making standard curve is fixed about 1.0〜1.5cm. S. 47 filter is more convenient for this colorimetry. The data were described in table 4 and fig. 4.

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