The mud rain and red snow phenomena are extensively observed in the mid-latitude region (30゜-50゜) of East Asia. The pH value, the concentration of chemical components, and the amount of eolian dust in 50 rainwater samples collected at Yashiro Town, Hyogo Prefecture from June 15, 1990 to June 7, 1993 were determined. Eighty percent of the rainwater samples collected were acid rain. Forty-one percent of eolian dust deposits in rainwater were dominated by the <20 μm fraction and their deposition were marked in spring. The origin of chemical species (X) was discussed by using the enrichment factor (E) as defined by E=(X/Na) rainwater/(X/Na) seawater, where Na^+ is used as a reference element for sea salt. The E factor was 17.8 for SO_4^<2->, 20700 for NO_3^- + NH_4^+, 20.8 for Ca^<2+>, and 11.8 for K^+, suggesting that SO_4^<2->, NO_3^-, and NH_4^+ were of air pollutant origin and Ca^<2+> and K^+ were of tropospheric eolian dust origin. Conversely, the E factors of Cl^- and Mg^<2+> were 1.1 to 1.0, respectively, indicating their sea salt origin. The annual deposition of nssSO_4^<2->, NO_3^-, and Ca^<2+> in rainwater was 3.10, 1.69, and 1.49 meq m^<-2>, respectively. The amount of Ca^<2+> deposited in rainwater was significantly correlated with the amount of <20μm eolian dust in rainwater, indicating that Ca^<2+> was dissolved from tropospheric eolian dust derived from China. the recent rainwater in the central and northern regions of China shows higher pH values and Ca^<2+> concentrations which are 1.7 times higher than the southern region of China, but the concentrations of SO_4^<2-> + NO_3^- in both regions are almost equivalent. The difference is explained by the influence of tropospheric eolian dust derive from deserts and the Loess Plateau in the NO_3^- were relatively high, the Ca^<2+> concentration in rainwater in Japan was very low as compared to that in the central and northern regions of China. Our data showed that calcite in the eolian dust was consumed to neutralize acidic components in Chinese and Korean rainwater and was changed from CaCO_3 to CaSO_4 in rainwater. This interpretation was supported by the data that the CaCO_3 content in eolian dust samples collected from red snow and mud rain in Japan markedly decreased with the spreading of industrialization and/or motorization after 1960 in Japan and after 1980 in China. The recent tropospheric eolian dust long-range transported from China to Japan contains a small amount of calcite, suggesting that it has a low neutralization capacity to acid rain in Japan.

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To clarify the genesis of humic acid in Ando Soils, plant residue of Susuki (Miscanthus sinensis), Sasa (Sasa nipponica), or Kashiwa (Quercus dentata) is incubated at 65℃, 75℃, and 90℃ with or without fresh volcanic ash from Mt. Sakurajima and/or water. Humic acids were extracted with 0.1 mol L^<-1> NaOH and analyzed RF and Δlog K values after incubation Genesis of humic acid was discussed with kinetic theory. The color of plant residues including fresh volcanic ash and water (F. V. A. W.) were changed with increasing incubation days from yellow to brown initially, and then from brown to black color. Plant residues with water only (P. W.) were also changed from yellow to reddish-yellow and then to black-brown. However the rate of changing color from yellow to black-brown in P. W. was later than in F. V. A. W. The color of plant residues with fresh volcanic ash and without water (P. F. V. A. non-W.) was not able to change to black-brown. The color of F. V. A. W. changed faster to black in the order of 90℃, 75℃, and 65℃. The form of humic acid from P. W. of Susuki and from P. non-W. of Susuki changed to B type and Rp type, respectively. The changing pattern of the form of humic acid from Sasa was similar to the pattern of Susuki that whereby the decrease in Δlog K is large in the initial stage of incubation and then increases in the RF value follows. In Kashiwa, however, the increases in RF occurred from the initial stage with a smaller decrease in Δlog K. Humic acid from F. V. A. W. of Kashiwa reached to A type humic acid as Susuki and Sasa at last. Microbiological analysis after incubation at 75℃ showed that the formation of humic acid is not influenced by microorganisms. Hence humic acid from Susuki, Sasa and Kashiwa could be formed faster to A type with fresh volcanic ash and water under non-microbiological and high-temperature condition. This fact means that fresh volcanic ash acts as a catalyst for changing to black plant residues.

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The scaling method was applied to obtain the empirical formula on soil-moisture characteristic curves for 90 samples taken from the soil layers at the depth of 0-10 cm and 10-20 cm in mulberry field, Fuchu Farm, Tokyo University of Agriculture and Technology, Japan. According to FAO/UNESCO classification the soil which we collected for experiments was Humic Andosol which consist of "Tachikawa Loam" derived from basaltic pyroclastic materials from Mt. Fuji. The results obtained were as follows : 1) The formula of S_e=[1+(ah)^n]^<-m> was successfully applied to soil-moisture characteristic curves of soil samples, where S_e : effective saturation degree, a, h and m : empirical constant, h : suction (m). 2) The scaling coefficient of the soil-moisture characteristic curves for soil samples was approximated to the logarithmic normal distribution. 3) Porosity, organic matter content and gravel content were important factors which affected the scaling coefficient of the soil-moisture characteristic curves for soil samples. 4) It was recognized from the semivariogram of the scaling coefficient that the distance between soil sampling sites should be more than 60 m when the sampling by the random method is to be carried out in this mulberry field. The number of extractions required to determe the soil moisture curve can be estimated using the scaling coefficient.

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To evaluate soil pollution by heavy metals, not only the total quantity of heavy metals but also the chemical forms in soils must be investigated. A method for fractionating heavy metals in soils was devised modifying McLAREN & CRAWFORD'S method and applied to chemical forms of copper, zinc and cadmium in several soils. 1) Using 0.1 M potassium pyrophosphate to extract the metals combined to the humic substances, Andosol B horizon that has little organic matter showed as much quantity of metals as A horizon that had much organic matter. A new method to extract the metals combined with the humus substances by using 2.5 % acetic acid after the decomposition of organic matter with H_2O_2 markedly decreased the quantity of metals sorbed by organic matter in Andsol B horizon, showing that this method is more suitable for soils with much amorphous materials. Acid oxalate extraction under UV irradiation did not completely extract metals occluded by the free iron oxide in Red Yellow soils. Ascorbic acid and acid oxalate completely reduced the oxides and extracted metals occluded by oxides. 2) Acetic acid at a concentration of 2.5% used to extract the metals specifically sorbed by free oxides was recognized to extract most of the heavy metals sorbed by goethite and gibbsite. 3) About half of soil copper existed in the residual fraction, namely in the crystal lattices. The amount of copper occluded by oxides and that combined by the organic matter were next to the residual fraction. Sixty to seventy percent of soil zinc was in the residual fraction, and the amount occluded by oxide was the majority of the other fraction. Cadmium in the fractions exchangeable and bound by inorganic sites were much more than copper and zinc. 4) Soil pollution increased the metals exchangeable and adsorbed by free oxides and organic matter that were considered to be in equilibrium with soil solution, and finally with the river water.

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The methanol extract of soybean (Glycine max L. cv. Tamahomare) roots contained a substance that inhibits the growth of a Bradyrhizobium japonicum strain 138 NR in a yeast extract-mannitol broth. The substance was isolated by partitioning to butanol, sequential use of a silica gel and Sephadex LH-20 column chromatography, and then purified by fractional crystallization. From 500 g fresh weight of soybean roots, 2.6 mg of the substance, a white powder, was obtained. Infrared, ultraviolet, fluorescence, mass, and nuclear magnetic resonance spectrometry identified the substance as 4', 7-dihydroxyisoflavone, daidzein. More than 1 μM daidzein inhibited the growth of the strain in the nutrient broth, with ED_<50> value of 2 μM. However, in the broth supplemented with 50 μM spermidine, 10 μM daidzein did not inhibit the growth of bacteroids of the strain, whereas completely inhibited the growth of the non-bacteroid form before inoculation to soybean.

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To gain the information of physiology and diagnosis of crop nutrition from the fluid analysis, an experiment was conducted. In the culture solution containing 2 or 7 mM Ca, komatsuna and grafted cucumber plants were grown, and analyzed for pH, EC and concentrations of cations (Ca^<2+>, Mg^<2+> and K^+) and anions (NO_3^-, H_2PO_4^-, SO_4^<2-> and Cl^-) from the xylem-exudating sap and fluids of petioles and leaf blades in lower and upper parts of crops. The pH in xylem sap was decreased in both crops, and the fluid pH in the leaves was similar to medium pH in komatsuna, while it was increased in cucumber leaf fluids. The EC values and concentrations of Ca and Mg were increased in xylem sap and leaf fluids. Increase in Ca and concentrations in the culture solution resulted in a decrease in Mg concentrations in leaf fluids of both crops, and a slight decrease in K concentrations in cucumber fluids. The Ca in the leaf blades was distributed in fluids by 60-88% in komatsuna and by 5-11% in cucumber, while Mg was distributed in leaf fluids by 79-103% in komatsuna and by 15-34% in cucumber. In both the petioles and blade fluids of the two crops, K concentrations were 100-150 mM, and 60-80% of total K was distributed to the fluids. The percentages of NO_3-N in total blade N were 11-25 in komatsuna and 2-10 in cucumber, pointing the high activity of nitrate reduction in cucumber leaves. In both crops, the H_2PO_4^- concentration were 2-4 mM in xylem sap, 4-9 mM in petiole fluids and 10-15 mM in blade fluids. The increase of medium Ca concentrations resulted in a decrease in H_2PO_4^- concentrations of cucumber leaf fluids. The ratio of meq of the total anions (NO_3^-+H_2PO_4^-+SO_4^<2->+Cl^-) to meq of the total cations (Ca^<2+>+Mg^<2+>+K^+) was nearly 1 in xylem sap in both crops and in petiole fluid of komatsuna, whereas the ratios varied from 0.2 to 0.8 in cucumber petiole fluids and blade fluids in both crops.

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The effects of hot water extract of cells of Chlorella vulgaris (chlorella extract) on relationships between the population of actinomycetes and the growth of radish seedlings were studied. The chlorella extract acted as a plant growth regulator as kinetin, not as GA_3 in elongation test of excised radish leaf sections. The amendment of chlorella extract to soil promoted the growth of shoots and roots of radish in both the sterilized and non-sterilized soils. The increase in the fresh weight of the plants was higher in the non-sterilized soil than in the sterilized soil, but the fresh weight of the root was not significantly different. The amendment of chlorella extract to soil also increased the population of actinomycetes and bacteria in soil, but not the population of fungi. There were significant positive correlations between the fresh weight of shoots and roots of radish and the population of actinomycetes. It was presumed that chlorella extract promotes the growth of radish seedlings acting directly as a plant growth regulator and indirectly through the increase of the population of actinomycetes in soil.

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The distribution of biomass and sulfur were determined for deciduous (Df) and coniferous (Cf) forests in a college experiment forest at Tomakomai (N. 42゜40', E. 141゜36') as the bases to study sulfur cycling in the forest ecosystems. The Df-forest consists mainly of Quercus mongolica var. grosserrata, Purnus sargentii, Acea mono, Tilia japonica, and other lower story broadleaved trees and its standing stock biomass (SSB) was estimated at about 240 Mg ha^<-1>. The Cf-forest, on the other hand, was a young plantation of Pinus strobus and its SSB was about 90 Mg ha^<-1>. The highest sulfur content was obtained in leaves for all the tree species followed by roots, branches, and trunks. The sulfur content of leaves varied in a wide range from 1 to 4 mgS g^<-1> depending upon age and position of leaves and tree species. The amounts of accumulated sulfur in the upper story trees of Df- and Cf-forests were estimated at 75 and 33 kg S ha^<-1>, respectively. Most of the accumulated sulfur (ca. 54%) was partitioned to roots and stocks in Df-forest, but in Cf-forest about 55% of it was found in branches and leaves. The organic horizons of forest soils were a fairly big pool of sulfur in the ecosystems, especially for Cf-forest. Although sulfur contents of the mineral soil horizons were very low, the accumulated sulfur in soils amounted to about 600 kg S ha^<-1> for upper 50 cm horizons. It was certain that the sulfur pool of mineral soil horizons plays an important role in controling sulfur cycling of the forest ecosystems under consideration.

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The rates of input, output, and cycling of sulfur in deciduous (Df) and coniferous (Cf) forests in a college experiment forest at Tomakomai were estimated. Because of the higher efficiency of conifers as the collector of dry deposition, the rate of atmospheric sulfur input (D) to the Cf-forest amounted to about 1.5 times that to the Df-forest. The larger D resulted in a higher ratio of cycling sulfur to accumulated or required sulfur of forest vegetation. For example, the D/R (R : required sulfur by forest vegetation) ratio of Df-forest was estimated at 1.4 but that of Cf-forest was 2.4. It is certain that the forest ecosystems in this area are accepting atmospheric sulfur input of far greater than that required to keep the reasonable net photosynthetic production. However, the direct influences of this excess sulfur input on trees and soils are, so far, not obvious. This may be due to the larger buffering capacity of big pools of upper story trees and soil horizons. However, cycling and leaching of basic elements are forced to accelerate under such a high rate of sulfur input. Especially in Cf-forests, the amounts of sulfur accumulated in upper story trees and soil organic horizons are increasing rapidly and abnormal defoliation is often reported. It is feared that degrading influences on upper story trees may be actualized if the excess sulfur input at present level is continued for a long time. We have to watch carefully changes of the biological activities of vegetation and material cycling in the forest ecosystems.

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