Soil physical properties and structures of the tissue in the peat layer (O1 layer) beneath the dressed mineral soil layer (approximately 10 cm in thickness) and the peat layer (O2 layer) just beneath the O1 layer were investigated in two grassland fields of 3 and 16 years after reclamation (3 yr. field and 16 yr. field). Both fields consist of peat layers with depths greater than 1 m. 1) The thickness of O1 layer plus O2 layer is about 25 cm. Alhough the major plant species of the O1 layer and O2 layer in both fields was Middendorf Sedge (Carex middendorffii Fr.Schm.), the decomposition degrees by von Post method of the O1 and O2 layers in the 3 yr. field were H2 and H3 respectively, while those both in the 16 yr. field were H6. This indicates that decomposition of peat in 16 yr. field proceeded more than that of 3 yr. field. 2) Although the tissue structure of the O1 layer of horizontal direction in the 3 yr. field showed compressed whole plant tissues in a stratified appearance, that of the 16 yr. field showed materials like the fibers of hemp palms and black glossy materials among the fibers. 3) Although the bulk density of the O1 layer in the 3 yr. field was 0.14 gcm^<-3>, that in the 16 yr. field was 0.22 gcm^<-3> ; 1.5 times greater than the 3 yr. field. The solid ratio of the O1 layer in the 16 yr. field was 0.11 cm^3cm^<-3>, more than twice as much as the level (0.05 cm^3cm^<-3>) observed in the 3 yr. field. The distribution of the volume of each pore-size of the O1 layer in the 3 yr. field was largely different from that of the 16 yr. field. 4) The ignition loss of the O1 layers in both fields were approximately 0.85 gg^<-1>. Fiber content of the O1 layer in the 16 yr. field was clearly less than that of the 3 yr. field. This indicates that the decomposition of O1 layer in 16 yr. field proceeded more than that of 3 yr. field, and coincided with the results of the decomposition degrees by von Post method. 5) Soil moisture suctions in the 16 yr. field at the soil survey were higher; namely, soil was drier than in the 3 yr. field. 6) The above mentioned matters indicate that not only shrinkage with dehydration but also decomposition of the 01 layer in 16 yr. field proceeded more than those in 3 yr. field.

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The effect of tillage pan formation on the growth of sugar beet was studied in the fine-textured Brown lowland soils with texture of SiC or SiCL. Chemical and physical properties of soils, soil water potential and sugar beet root distribution in the early, middle and latter growth periods were measured for each soil type of fine-textured Brown lowland soil with texture of SiC or SiCL, medium-textured Brown lowland soil, Andosol and Wet Andosol. Physical properties of soils were favorable in the order of medium-textured Brown lowland soil, Andosol, Wet Andosol and fine-textured Brown lowland soil. On the other hand, chemical properties of soils were favorable in the order of fine-textured Brown lowland soil, medium-textured Brown lowland soil, Andosol and Wet Andosol. It was clarified from the changes in soil water potential and percentage of gaseous phase that the movement of soil water in the fine-textured Brown lowland soil was controlled to a larger extent by the percentage of the pore filled with gravitational water than that in the other soils. Therefore, the decrease in the percentage of pore filled with gravitational water due to the formation of tillage pan is considered to influence to the deterioration of drainage and to the restriction of water uptake by the crop root. Root penetration in the early growth period showed no significant difference among soil types, where the root was distributed in the plowed layer. In the middle growth period, the root penetrated to the plowed layer and middle layer in the fine-textured Brown lowland soil. In the other soils, the root was distributed below the middle layer. In the latter growth period the root in the fine-textured Brown lowland soil penetrated below the middle layer. The growth and yield of sugar beet were the worst defective in the fine-textured Brown lowland soil. The growth in the middle growth period influenced the growth in the latter growth period. It is considered that, in fine-textured Brown lowland soil, soil water environment was deteriorated and the root penatrartion was restricted due to the formation of tillage pan. Therefore, the water uptake by root was suppressed until the middle growth period due to the deteriorated soil water condition. As a result, it is considered that the formation of tillage pan is responsible for the inferior growth and yield of sugar beet in the fine-textured Brown lowland soil.

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We investigated several properties of water-stable soil aggregates giving special attention to macroaggregation (>0.25 mm), using 3 volcanic (group A) and 3 non-volcanic (group B) ash soils. 1) The contents of organic C (C), hydrolyzable carbohydrate (HC), readily hydrolyzable hexose (RH), and dithionite-citrate-bicarbonate soluble Al and Fe in the bulk soils and the aggregate size fractions were much higher in group A than in group B. 2) Among the macroaggregate size fractions of group A, the contents of the organic components such as C, HC, and RH generally increased with increasing aggregate size. The Al tended to be concentrated in the 0.25 to 1.0 mm size fractions. On the other hand, in group B, the organic and inorgaic components showed decreasing tendency with increasing aggregate size. 3) In group A, larger amounts of C, HC, RH, Al, and Fe were distributed in the macroaggregate than in the microaggregate size fractions. No such trend was observed in group B. 4) The degree of macroaggregation was much higher in group A than in group B. In group A, the higher the RH and Al contents, the higher the degree of macroaggregation. No such relationship was observed in group B. 5) From the results obtained, it was suggested that active Al and microbial polysaccharides merit close attention as the factors in the macroaggregation of group A, although the significant factors in group B remained unclear.

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The pumice layer was derived from the northwest fringe of Taal Volcano somma in Kaybagal, Tagaytay City in the Philippines. It has a gravel diameter of 3 to 5 centimeters (cm). The pumice gravel has a yellow surface color and a black inner color. These were observed using an optical microscope and scanning electron microscope (SEM). The chemical and mineralogical constituents were determined using a electron probe micro analyzer (EPMA), and X-ray diffraction apparatus. The results obtained from the optical microscope and SEM showed bubbles in the black or inner part of the pumice, while the surface showed weathered fine particles. Some of the bubbles observed were also partly weathered. The X-ray diffraction pattern showed smectite as the predominant mineral in the yellow surface layer, while amorphous materials were predominate in the black inner part. We speculate that smectite of the pumice may result from the weathering of amorphous glass in the inner part of pumice.

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"Classification of Cultivated Soils in Japan, third approximation" was examined to be applied to soil maps of cultivated field in which the second approximation was used for mapping. The existing soil profile descriptions and soil analysis values in Hokkaido and Toyama Prefecture were also used for examination. On the way of applying the third approximation to the soil maps, there occurred some problems, e.g. all item did not answer the card of soil profile descriptions, the differentiating criteria were different from the third approximation, and the soil analysis values were not accurate. It could be solved considerably by using the existing data as much as possible, and adding presumption and prediction. Moreover, soil maps were already different from the current state because of the change of the soil which was mainly caused by the farm land consolidation. Farm land consolidated can be comparatively easy to be specified, and the soil can be classified through using a simplified soil survey method. The third approximation had also some problems; 1) Some soil name of the second approximation was changed, for example, Andosols to Lowland soils or Volcanogenous Regosols. This is a result from using the quantitative definition and "keyout" method, which is unavoidable for a precise and objective classification, 2) As for dressed peat soils, the limit of the inorganic surface would be too thin, 3) Shapes of mottle used for definition of the hydromorphic soils such as Lowland soils is difficult to say to generalize. The definition of shape would be popular by means of publishing such a manual, 4) A quantitative boundary of the upland and the mountain is not definite, 5) It is necessary to examine parent materials quantitatively, and to treat properly the pumicious flow and the pyroclastic flow deposit, 6) The subsurface soil is not defined when it consists of two or more layers, 7) It is necessary to eliminate the contradiction on a soil code, and on the names of soil subgroups and soil series groups. It is necessary to organize the committee that authorizes the modification of the system of the cultivated soil classification systematically.

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