Chemical characterization of humic acids in soils with different fertilization histories was examined by Curie-point pyrolysis-gas chromatography-mass spectrometry. 1) Pyrograms of each soil humic acids showed a lot of peaks. The compounds of heat decomposition in Shakudo soil humic acids produced larger quantity of benzene, toluene, acetic acid, cresol, tetramethylphenol and three unidentified compounds. In addition to these decomposition products, Nose soil humic acids produced plentiful acetic acid. 2) The multivariate statistical programs of cluster analysis classified pyrograms as to groups of Tomikura soil humic acid and the other soil humic acids. The dendrograms of humic acids which were extracted from Nose soil with no nitrogen fertilizer and from Shakudo and Nose soils with fertilizer treatments showed that they belonged to the same cluster. 3) In the principal components with the principal component analysis in the pyrograms of soil humic acids the total cumulative variance was retained as 89.84%. The data to distinguish between Tomikura and the other soil humic acids were present in the first principal component, and it existed in the second principal component at Nose soil humic acid (organic matter and total improvement treatment) and also existed in the second principal component at the humic acid of Hoteiaoi treatment. And in the Nose soil humic acids of no nitrogen fertilizer and chemical fertilizer treatments it may be present in the third principal component. 4) The results of the factor analysis suggest that the amounts of benzene, methoxyphenol, furfural and two unidentified compounds are available as the indicator of qualitative variation of soil humic acid.

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Characterization of effects of earthworms (Pheretima communissima) habitation on soil organic matter was examined by Curie-point pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). 1) Phyrograms of the dung oil of earthworm and the plow layer (depth 0-10 cm) (except a control soil (Masa soil) without earthworm as a habitant and middle layer (depth 10-20 cm) soils) showed a lot of peaks. 2) The multivariate statistical programs of cluster analysis correctly classified pyrograms as four groups of soils. The relative coefficient between the dung soil and the plow layer was 0.982. 3) Among the first to the three principal components in the principal component analysis of the soil organic matter, 82.1% of the total cumulative variance was retained. The data to distinguish between the control soil and the dung soil were present in the first principal component, and it existed in the second principal component at the abundance of organic matter. 4) The factor analysis showed that 3-methylfuran, acetonitrile, 1-etylpyrrole, 2-methoxy-4-methylphenol and unidentified compound (7) were available as the common large loading compounds to exist among the first to the third factor.

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Comparative study was performed to estimate and compare the recovery rates of N, S and P in added organic matter or chemical fertilizer source in a greenhouse experiment. Fermented poultry manure, cattle manure compost and root residue of Italian ryegrass (Lolium multiflorum L. cv. Waseyutaka) were used as the organic matter source, while ammonium nitrate, potassium phosphate and potassium sulfate served as chemical source for N, S and P respectively. Treatments consisted of two soil types (regosols and andosols), three kinds of organic matter sources. chemical fertilizer source in a factorial experiment. Wagner pots of size (1/5,000 a) were filled with soil and organic matter or equivalent chemical contents provided as fertilizer and the control which contained soil and other mineral nutrients, except for the element under investigation. Depending on the source, the concentrations of N, S, P and C/N ratio of organic matter varied considerably. African millet (Eleusine coracana G_<AERTN>, Snow Brand) was used as an estimate of the mineral recovery. 1) The recovery rates of N and S in added organic matter, especially in root residue which had high C/N ratio were extremely lower than those of the chemical fertilizer. Furthermore it was observed that application of organic matter with a high C/N ratio, such as root residue may result in N and S deficiency in grasses. 2) Generally, the recovery rates of P in organic manure application, especially poultry manure, were higher than that of chemical fertilizer. This was more pronounced in the andosols which have low pH and high phosphate absorption coefficient.

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Soil physical properties of grazing land and meadow may vary due to differences in management and animal activity such as animal trampling. This may also affect the growth of the cultivated forage crops. To evaluate how soil physical properties and growth of African millet (Eleusine coracana, G_<AERTN>) is affected by soil compaction, three levels of compaction and four different soil textural classes were used for a frame experiment. Soil physical properties such as air permeability, three phases and hardness of soils and oxygen diffusion rate were measured. Total root length, tops and root weight and their mineral contents were determined. Similar parameters were also measured for grazing land and meadows. In the frame experiment, soil compaction increased the solid phase and hardness of soils, while air phase and permeability of soils in the upper 10 cm were decreased. Similarly, tops and root weight and total root length of African millet were decreased by soil compaction. Effects of soil compaction on the soil physical properties measured varied depending on the sand content. Regardless of level of compaction, the growth of African millet increased with increasing sand content. Significant differences were observed in the air permeability, soil phase and hardness of the upper 10 cm of grazing land and meadow, while no significant differences in their soil chemical properties were observed. Coefficient of air permeability of grazing land was observed to be lower than that of meadow. However, values for soil hardness and solid phase of grazing land were significantly lower than that of meadow. Forage fresh yields in grazing land were significantly lower than that of meadow. Coefficient of air permeability used as a index of soil air permeability was highly correlated with growth and total root length. Among the several soil physical properties considered, coefficient of air permeability was the best index to measure soil physical properties in relation to growth of African millet under soil compaction.

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Soils applied with different rates of farmyard manure (FYM) or compost were fractionated according to the particle size and the amounts of total C and N, mineralized N during 4 weeks of incubation at 30℃ and muramic acid were analyzed in each fraction. The soils used were sampled from three experimental fields in Japan : Togo (Red-Yellow soil ), applied with FYM at the rate of 0 to 20t/10 a for 8 years ; Kuriyagawa (Ando soil), applied with FYM at the rate of 0 to 32t/10 a for 10 years ; Fujisaka (Ando soil), applied with compost at the rate of 0 to 3.4t/10 a for 43 years. The long-term application of FYM or compost increased the total carbon and nitrogen contents of each particle size fraction, and the relative increase in the amount of organic matter was largest in coarse sand size fraction (>210 μm). The increase in organic matter in coarse sand size fraction due to the organic matter application was remarkable in the soils that received a large amount of FYM, i. e., from Togo and Kuriyagawa. The application of organic matter also increased the amount of mineralizable organic N in each fraction, and the percentage mineralization of organic N was the largest in coarse sand size and clay size (<2 μm) fractions of the soils applied with organic matter. From the distribution of mineralizable N among the particle size fractions, the most important fraction contributing to the N mineralization was the coarse sand size fraction for the Red-Yellow soil whereas the clay size fraction for the Ando soil. The concentration of muramic acid in particle size fractions increased with the increase of the amount of applied organic matter except for the coarse sand size and fine sand size (20-210 μm) fractions of soils from Fujisaka. Significant correlations between the concentrations of muramic acid and the amounts of mineralized N in individual fractions were observed with exception of the fine sand size fraction of the Ando soils. This finding suggested that the microbial cell wall materials were serving as a source of readily mineralizable N in soils applied with organic matter.

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Micromorphological observations have been made for different types of wet lowland soils to obtain information on their characteristics and genesis. 1. Anthraquic soils (Paddy soils) Genesis of anthraquic soils involves unique pedogenic processes including the development of iron accumulation horizons and plowpan, and a subsurface greyization which spreads from the surface downwards. 1) Thread-like iron mottles along root channels are common to iron accumulation horizons. These mottles consist of channel ferran associated with neoferran. The horizons are reducing under a flooded condition. After drainage Fe^<2+> in the soil matrix moves toward root channels and is oxidized when it meets the oxygen which comes down through the channel. 2) Greyizeed subsurface soil is characterized by iron-depletion cutan (alban of neogleyan) on ped-faces and along conducting channels and by ferruginous mottles with diffuse boundaries in the matrix , which indicates a reductive eluviation along macro-voids and in situ segregation of iron in the matrix. 3) Migration of suspended matters is evident. Clay coatings on ped-faces, and channel walls are often observed in greyized subsurface soils. Flood coatings (gleyan) or poorly sorted illuvial materials are also common on ped-faces and channel walls. 4) In anthraquic soils a plowpan develops beneath the plowlayer to keep the lands flooded. Micromorphologically it is well expressed in the amount of macro-pores, which is at a minimum in plowpan. 2. Groundwater aquic soils (Gley and Gray Lowland soils) Tube-like iron mottles are characteristic of Gley and Gray Lowland soils. Tube-like mottle consists essentially of neoferran with or without ferran. Film-like iron mottles (ped-ferran) are also common in aquic lowland soils. Fe^<2+> in the matrix moves by diffusion toward macro-pores and meets oxygen at or around the surface of the pores. 3. Organic soils Fibric, hemic and sapric materials were used for observation. Degree of decomposition of organic matter is well reflected in the ratios among undecomposed weakly birefringent plant residues, partially decomposed opaque plant debris and humified massive or granular colloidal materials.

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The dry matter production and uptake and partitioning of N and p in a high-yielding semidwarf rice variety, Suweon 258, were investigated in comparison with those of a Japonica variety, Musashikogane, from 1984 to 1988. 1) The total grain number of Suweon 258 was correlate with the sum of daily mean temperature and the accumulated sunshine radiation for 40 days before heading (r=0.9465*, r=0.9183*, respectively). 2) The total N and P uptake of Suweon 258 before heading were correlated with the sum of daily mean temperature before heading (r=0.9839**, r=0.9390**, respectively). The dry matter production of Suweon 258 before heading was correlated with the summation of sunshine radiation before heading (r=0.8825*). 3) The partitioning ratio of N and P to the grains of Suweon 258 were correlated with the sum of daily mean temperature after heading (r=0.9519**, r=0.9675**, respectively). The high ability of grain production and nutrient uptake and partitioning to the grains of Suweon 258 were seriously affected when the intensity of sunshine and air temperature were low. Suweon 258 showed the high production ability under favorable weather conditions.

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Methane (CH_4) emission from flooded paddy soils to the atmosphere through rice plant was suppressed to 58-2% of control by percolation at the rate of 1 liter/2 weeks (26 mm of water column/week). Dissolved gases in he leachate were composed mainly of CO_2, being larger in the early and late stage of flooding. Dissolved CH_4 increased in the middle stage and decreased by interruption of flooding in the late stage. Both dissolved CO_2 and CH_4 increased by amendment of rice straw. Organic acids such as acetic and propionic were found sometimes in the leachate, but the amounts were small in comparison with dissolved CO_2 and CH_4. Dissolved O_2 and nitrate in the leachate decreased quickly to negligible amounts. Effect of percolation was not markedly found on soil Eh (5 cm). Mechanism of suppression to CH_4 emission by percolation was, probably, mainly due to removing dissolved CO_2 in the leachate.

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The influence of continuous compost (cow dung-rice straw) application on the activities of protease, β-acetylglucosaminidase, and adenosine deaminase in soils of upland fields, changes in their activities during the incubation of soils, and relationships between the enzyme activities and the amounts of nitrogen mineralized during the incubation were investigated. The results obtained are as follows : 1) The activities of protease, β-acetylglucosaminidase, and adenosine deaminase in soils of upland fields were remarkably increased by continuous compost application. The degree of increase significantly varied with the kinds of enzymes and soils. 2) When the soils without and with compost application were incubated at 30℃ for 7 weeks under the moist conditions, the activities of adenosine deaminase and especially protease decreased to a larger extent in the soils without compost than in the soils decreased or increased, and the degree of increase was evident in the soils with compost. 3) Protease activity was highly correlated with the amounts of nitrogen mineralized during the incubation of soils (r=0.793, significance at 2% level). A high correlation was also found between the activity of β-acetylglucosaminidase and the amount of nitrogen mineralized (r=0.708, significance at 5% level). However, such a relationship was not found for adenosine deaminase.

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Electric charge characteristics of Andisols in northern Japan were studied by measuring the retention of NH_4^+ and NO_3^- and its problems on soil management were elucidated with special reference to their colloidal composition. The remarkable development of negative charge with increasing soil pH was common to all Andisols and was highly related to the amount of soil organic matter. This variable charge property required a large amount of chemical for liming and caused easy leaching of cations toward subsoil when there was much rainfall decreasing soil pH. Some constant negative charge derived from 2 : 1-2 : 1 : 1 minerals were found in nonallophanic Andisols and Al toxicity was thought to be one of the major problems in these soils. Compared to CEC, AEC of Andisols was relatively small and was actually zero at pH 6. Therefore, nitrate, the major form of mineral nitrogen for upland crops, was easily moved into subsoil after heavy rain. Development of positive charge in Andisols was significantly depressed by the presence of organic matter. Growth and nitrogen uptake of upland crops in Andisols were remarkably influenced by subsoil acidity. Therefore, we should pay attention to the electric charge characteristics of Andisols in soil management.

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We examined the iron-deficiency response on hairy root and intact plant. We used the cucumber (Cucumis sativus L. cv.) for test plant. Both hairy root and intact plant root secreted riboflavin as a result of iron deficiency. Therefore, there was a negative correlation between riboflavin secretion and iron content in plant. After we confirmed that riboflavin did not dissolve Fe_2O_3, we also examined the dissolution of Fe_2O_3 by the hairy root. The hairy root dissolved Fe_2O_3. Iron-deficiency hairy root had higher ability to dissolve Fe_2O_3 than iron-sufficient hairy root. From the above results, we considered the dissolvable functions of water-insoluble ferric compounds are induced by iron deficiency and exist in the root.

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Rapid analysis of exchangeable cations and CEC of soils by a shaking extraction method, which can get similar values to semimicro S_<CHOLLENBERGER> method, was studied. Procedure of the method established is as follows ; Place 2.00 g of <2 mm air-dried soil in an 85 ml Nalgene centrifuge tube. Add 30 ml of 1 M ammonium acetate (pH 7), and shake for 15 min. Centrifuge the tube at 2,500 rpm for 3 min. Decant the supernatant into a 50 ml Buchner funnel fitted with filter paper, and receive the filtrate in a 100 ml volumetric flask. Repeat extraction two more times in the same manner except shaking for 30 s by hand. Add 5 ml of 20,000 ppm Sr into the flask, and make to volume with ammonium acetate. Determine Ca, Mg, K, Na and Mn by ICP-AES using calibration method. To remove free ammonium ion from the soil, add 20 ml of 80% methanol in the centrifuge tube, shake for 30 s by hand, centrifuge, and discard the supernatant through the funnel used on the extractions. Repeat this step two more times. Add 30 ml of 10% potassium chloride in the centrifuge tube, and extract absorbed ammonium ion from the soil in the same way with extracting exchangeable cations using funnel used in previous steps. Make to volume with 10% potassium chloride, dilute 5 times with water, and determine ammonium ion by an ammonia electrode method. The values obtained by this method agreed well with the values obtained by semimicro S_<CHOLLENBERGER> method on exchangeable cations and CEC of 24 soils. All extraction procedures of the method can be finished within 2 h per one sample. Repeatability of the method was about 5% for exchangeable Ca, Mg, K, and about 10% for CEC as coefficient of variance.

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[in Japanese]

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