The made lands brought about by Agricultural Development Programs are said to be one of causes of runoff soils owing to the soil erosion. It is an urgent need in Okinawa island to study the cause and process and the efflux of soils, and to prevent and remove runoff soils. The objective of this study was to investigate the physical properties of the surface soils and the runoff soils of the made land of Okinawa island. Samples of surface and runoff soils were collected from ten selected sites. The collected samples were known in Okinawa dialect as: "Kunigami Mahji" (red and yellow soil or the other stone soil, strong acidic); "Shimajiri Mahji" (dark red soil or Ryukyu-limestone soil, neutral to weakly acidic); and "Jahgaru" (grey upland soil or mudstone soil, alkaline). The results are summarized as follows: 1) The value of the clay, dispersion ratio and erosion ratio of all soil samples were higher than each of criteria for the erodibility; 2) A positive high correlation between dispersion ratio (Dr) and/or erosion ratio (Er) was observed the content of the soil particles (CSP) dispersed by distilled water alone. It seems possible to estimate the both ratios and judge the erodibility by using the regression equations which were as follows: Y= 103.25X+10.06 [where Y=Dr (1/20)% and X=CSP (kg/kg oven-dry soil) in the soil particles less than 0.05 mm, r=0.956*** (significant at 0.1% probability level)]; Y=102.10X-3.84 [Where Y=Er(1/20)(%) and X=CSP in the soil particles less than 0.05, r=0.891***]; Y=130.76X+1.20 [Where Y=Dr (1/50) (%) and X=CSP in the soil particles less than 0.02 mm, r=0.987***]; Y=105.01X+0.40 [Where Y=Er(1/50) (%) and X=CSP in the soil particles less than 0.02 mm, r=0.982***]; 3) The texture of surface soils was light clay in the both soils of "Kunigami Mahji" and "Shimajiri Mahji", and heavy clay in "Jahgaru". "Kunigami Mahji" had the highest gravel content. There was also a tendency for "Kunigami Mahji" to have high sand fraction in the surface soils of made land, and to have high clay and silt fractions in the runoff soils. "Kunigami Mahji" had the most distinctive soil color in water. It was expected that the amounts of runoff soil of "Kunigami Mahji" were smaller than those of the two others.

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Silica concentration in river water and soluble silica and aluminum in soil were researched in potato production areas in Niseko and Kuriyama regions (potato scab suppressible area) and Abashiri region. The results are as follows: 1) Silica concentration in river water tend to low level in the western and high level in eastern Hokkaido. 2) Silica concentrations in river water were from 10 to 20 mg kg^<-1> in Niseko and Kuriyama regions. On the other hand, the silica concentrations were from 10 to 46 mg kg^<-1> in Abashiri region, especially, the silica levels were over 40 mg kg^<-1> in the river water which was filtered through the Brown Andosols. 3) The soil samples were extracted with 1 N sodium acetate of pH 4.0 to know about the relationship between soluble silica and aluminum in soil samples. The average value of soluble SiO_2 are 200 mg kg^<-1> in Niseko and Kuriyama regions, and 440 mg kg^<-1> in the Brown Andosols of Abashiri region. The average of soluble Al in Niseko, Kuriyama regions in 440 mg kg^<-1>, and the maximum value is 1060 mg kg^<-1>. On the other hand, the average of soluble Al in soil samples of Abashiri region is 250-300 mg kg^<-1> at each soil types. 4) Both Niseko, Kuriyama and Abashiri regions show high values of the coefficients of correlation between soluble silica and soluble Al. the averages of Si/Al mol ratio are 0.23 in all soil samples of Niseko, Kuriyama regions, and 0.48 in Ordinary Andosols, 0.54 in Acid Brown Forest soils, 0.67 in Brown Andosols of Abashiri region. 5) Exchange acidity y_1 was in inverse proportion to soluble Si/Al ratio in soil, and was increasing geometrically below 0.5 of the Si/Al ratio. 6) From the above results, it is concluded that a low level of soluble Al is due to a stable compound such as aluminum silicate by a high level soluble silica in Brown Andosols of Abashiri region.

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In this investigation, the particle size distribution of Akahoya soil was determined to understand the relationship between the degree of weathering and depth from the land surface of Akahoya soil. Akahoya soil can be divided into three types of group mainly based on the depth from the land surface. Type I, Type II, and Type III are buried at less than 150 cm, about 200-400 cm and 300-700 cm from the land surface, respectively. Akahoya soils are dominant in fine sand particles, the contents of which change in relatively wide range among Akahoya samples. Correlation between the clay and fine sand contents (%) of Akahoya soils showed close negative relationship. It is important to point out that clay particles originated from fine sand particles, as a result of weathering of these particles. Coarse sand contents of Akahoya soils abrubtly increase with decreasing distance from its origin and retain main characteristics of tephra fall. On the other hand, the silt contents of Akahoya soils exhibited the least change in the proportion which ranges from 17.3-28.6% compared with the other soil particles. Moreover, parent materials (Akahoya tephra (f_3)) of Akahoya soils were estimated to contain 70-75% fine sand. The clay contents are useful in estimating the degree of weathering of the three types of Akahoya soils and that the rate of weathering is in the order of Type I>Type II>Type III. This fact suggests that weathering of tephra fall progresses more rapidly on the land surface than in the underground.

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The purpose of this study is to establish a method for soil survey of Andosols, including soil layers deeper than one meter. In this report, deep layer soil s were defined as soils consisting of surface soil layers (shallower than one meter) and deep soil layers deeper than one meter, as far as the water table, or several meters deeper to the lithic layer. Deep layer soils were surveyed at made-land farm fields, which were prepared through the reclamation in Hayakita, southwest Hokkaido. The surface soil type was Andosol with coarse texture. The deep soil layers consisted of pyroclastic fall (tephara) layers over deposit layers of the late Quaternary period and sedimentary rock layers of the Tertiary period. The distribution of these deep soil layers, which appeared on the surface through reclamation of this area, was clarified by conducting a soil survey using soil auger, conducting a geological survey of outcrop cut, making isopach maps of tephra layers and classifying the topography with aerial photographs. Thereafter horizontal and vertical maps of the made-land area could be prepared. The results revealed that there is a relationship between the type and the depth of soil layers, by using the contour maps of the made-land cut by reclamation. Before land reclamation, reconnaissance maps of the deep layer soils were prepared using isopleth maps for the depth of cutting estimated from the reclamation plan contour maps. The distribution of rock layers was predicted by the geologic mapping method. The reconnaissance map was very similar to the soil map prepared by conducting an actual soil survey of made-land after reclamation, with differences in only the thickness of the layers and the extending direction of the rock layers. The reason for these differences may be due to the different landforms at the boundary between hills and plateaus in this area.

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SDF-21 is a compound fertilizer containing plant growth retardant (uniconazole-P). For the effective application of SDF-21, it is necessary to investigate the factors that affect the behavior of uniconazole-P and fertilizer nutrients in paddy soils. In this study, we investigated the retention and movement of uniconazole-P and fertilizer nutrients (especially for NH_4^+-N) in paddy soils. 1) When SDF-21 was supplied to the soil surface, the fertilizer nutrients in SDF-21 diffused rapidly to liquid phase. However, most of uniconazole-P was adsorbed by the paddy soil. NH_4^+-N moved downward deeper than 5 cm, but uniconazole-P remained in a surface-layer within 2 cm in depth. As little amount of uniconazole-P dissolved in the flooded water, the effect of uniconazole-P on shortening culm length was observed only in the area where SDF-21 was applied. 2) When the soil were not submerged, the effect of uniconazole-P did not appear. However, leaf color index was increased by the application of fertilizer. This result suggested that this effective moisture level for uniconazole-P was different from that for the fertilizer nutrients.

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Twelve varieties of crop seedlings were grown without sodium salt (control) and in the presence of different kinds of sodium salts (Na; 80 mmol L^<-1>), namely, NaCl, Na_2SO_4, NaH_2PO_4, and NaNO_3 in order to compare the effects of NaCl with the other salts on the absorption of the cations, K, Ca and Mg. The results obtained are as follows: 1) Crop responses to the absorption of the cations, especially K^+, were almost the same although counter anions were varied. 2) There were significant negative correlations between the ratios of the absorption rate of the cations and the equivalent ratios of Na/counter anions in plants. 3) Sodium chloride and NaNO_3 showed higher effects on the absorption of the cations than Na_2SO_4 and NaH_2PO_4 treatments. The ratios of K^+ absorption rates were >1 in soybean, corn, every 2 varieties of kidney bean and pumpkin. For Ca^<2+> and Mg^<2+>, the ratios were >1 at NaCl and NaNO_3 in soybean, azuki bean, every 2 varieties of kidney bean and pumpkin. The ratios were <1 at Na_2SO_4 and NaH_2PO_4 in almost all crops. 4) It was suggested that effects of changing counter anions on absorption of the cations, especially Ca^<2+> and Mg^<2+>, were due to their physiochemical characters rather than physiological character, because the ratios of the absorption of two-valenced cations were lower in SO_4^<2-> and H_2PO_4^- than in control or Cl^- and NO_3^-.

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The increase in the amount of ammonium nitrogen in the soil which is air-dried before flooding is called "air-drying effect" and it is considered as the whole amount of available nitrogen. In most studies, the difference between the amounts of ammonium nitrogen after incubating air-dried and non air-dried soil is measured and this difference is explained as the promotion of nitrogen mineralization. The amount of ammonium nitrogen accumulated after incubation is the difference between the mineralized nitrogen and the nitrogen transferred from the ammonium pool. Therefore, we cannot simply conclude that this difference is caused by the promotion of nitrogen mineralization. In this paper, we tried to evaluate the nitrogen mineralization itself in the soil with and without air-drying treatment before flooding using ^<15>N tracer technique. 1) The change in the amount of nitrogen mineralized was not correlated to that of the amount of ammonium nitrogen. Therefore, we cannot know the amount of nitrogen mineralized by means of measuring only the amount of ammonium nitrogen in the soil. 2) In the air-dried soil, the amount of nitrogen mineralized increased 2-5 times more than in the soil without air-drying treatment within 3-6 weeks after flooding. After that period, the amount of nitrogen mineralized decreased, but nitrogen mineralization did not cease. 3) Judging from the results obtained, we confirmed that air-drying treatment before flooding promoted nitrogen mineralization. And the amount of nitrogen mineralized in the some incubation period does not mean the whole amount of available nitrogen.

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The heating temperature and heating time of the volcanic ash soils were investigated in order to enlarge phosphate removing capacity of the volcanic ash soils. The effects of addition of ferrous sulfate (FeSO_4・7H_2O) and poly aluminum chloride (PAC) to the volcanic ash soils before heating on phosphate sorption coefficient were also studied. 1) Phosphate sorption coefficient of the heated volcanic ash soils increased with heating temperature till 500℃. While, high heating temperature (>600℃) extremely decreased the phosphate sorption coefficient. The heating time scarcely affected the phosphate sorption coefficient. The best condition of heating was at 400-500℃ for 5 min, judging from the phosphate sorption coefficient, the crumbliness in the water and the cost. 2) The addition of FeSO_4・7 H_2O to the volcanic ash soils increased better phosphate sorption coefficient of heated materials than no addition of FeSO_4・7H_2O. 3) The addition of PAC 4%, 8% to the volcanic ash soils increased phosphate sorption coefficient of heated materials. But the addition of PAC 16% to the volcanic ash soils scarcely affected phosphate sorption coefficient of heated materials.

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Groundwater, which was used for agriculture, was sampled from 161 points in China prefecture. These concentrations were determined and the groundwater quality was classified by using multi-variate analysis . The results were summarized as follows: 1) There were five regions according to aquatic quality in Chiba prefecture. They were volcanic ash soil region, paddy field in ravine region located between volcanic ash terrace, fluvial loamy soil region, marine sandy soil region, and Tertiary clayey soil region. The results of principal component analysis supported this classification into five regions. 2) The first component derived from principal component analysis denoted the characteristics of composition and concentration of each element in groundwater. The second component indicated the characteristics of acidity and concentration of acid substance in groundwater. The third component showed the characteristics of redox condition of groundwater. 3) The results of cluster analysis showed a close relation among the groundwater quality in volcanic ash soil region, that in fluvial loamy soil region. That in Tertiary clayey soil region and that in marine sandy soil region differed from that in the aforesaid three regions. 4) Concentration of each element of groundwater in volcanic ash soil region was the lowest. Those in fluvial loamy soil region and Tertiary clayey soil region were lower next to that in volcanic ash soil region. The concentration of NO_3-N in paddy field in ravine region, and the concentration of Ca, Na, Fe, Cl, SO_4-S, B, and the values of EC and alkalinity in marine sandy soil region were the highest among the five regions.

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