We indicated in the previous paper that plant culture soil was easily manufactured by mixing and composting plant residues with sludge derived from water purification process. However, the contents of available phosphate and exchangeable calcium (Ex-Ca) in plant culture soils previously reported were markedly low, and it seemed to be responsible for the retardation of plant growth. In this paper, plant culture soils were manufactured by mixing and composting plant residues with sludges from water purification process under the supplementation of superphosphate and formed calcium silicate. Plant residues used in this experiment were tall golden-rot, mugwart, Japanese plume-glass, soybean, corn and black wattle. The results obtained were as follows. 1. Decomposition of any plant residues measured by the losses of dry matter, carbon and nitrogen rapidly occurred within the first one month after composting, and then the decomposition rate gradually became low, although it depended on plant species. In addition, it was recognized that the rate of decomposition was higher in order of corn>toll golden-rot>soybean>mugwart>black wattle>japanese plume-glass. There was a negative correlation between carbon content in plant residues and dry matter loss. 2. Nitrate nitrogen (NO_3-N) content of plant culture soils manufactured in this experiment was affected by plant species. Namely, the content was the highest in the plant culture soil made from soybean residues, and conversely was the lowest in the culture soils made from japanese plume-glass. Moreover, it was recognized that with the elapse of composting period, the NO_3-N content of plant culture soils made from soybean and corn residues decreased, while plant culture soils made from mugwart and black wattle increased. 3. Supplementation of superphosphate and formed calcium silicate resulted in the remarkable increase of available P_2O_5 and Ex-Ca contents in plant culture soils. 4. Growth of komatsuna, used as that plant, was higher in any plant culture soils manufactured than in control soil (fertilized soil). Consequently, it was considered that the plant culture soils manufactured by mixing and composting sludges from water purification process with plant residues gathered from arable land were useful as pot culture soils for rearing of vegetable seedlings.

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We carried out experiments to compare the composition of the extractable organic substances between the heated (50, 100 and 150℃) and fumigated soils in order to clarify the origin of the nitrogen mineralized by soil heating treatment. The soils in order to clarify the origin of the nitrogen mineralized by soil heating treatment. The soils used were Dark Red soils (Kamogawa soil) and Andosols (chiba soil). The extractable total organic C and N, the extractable saccharides (hexose and pentose) and the various forms of the extractable N (amino acid N, amino sugar N, amide N and ammonium N) were measured. In the Kamogawa and chiba soils, the composition of the extractable organic substances in the soil heated at all temperatures was out of accord with that in the fumigated soil, suggesting that the extractable organic substances in the heated soil in the two soils were derived from both biomass and non-biomass fraction. The difference in the extractability between hexose and pentose in the heated soil was observed. The amount of extractable amino sugar N in heated soil was more than that of extractable amino acid N, suggesting that amino sugar N would be a key compound as a source of nitrogen mineralized by heating treatment. Large amount of the ammonium N in the soil heated at 150℃ was observed. We considered that this phenomenon could be attributed to the deamination of organic N, especially amino sugar N by the heating treatment at high temperature.

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It is known that soybean nodules contain leghemoglobin and leghemoglobin content of soybean nodules is related to nitrogen fixation activity. Nitrogen fixation activity of soybean detected by carbon dioxide evolution was not inhibited. By suppling carbon monoxide, hydrogen generation was enhanced corresponding to the decrease of acetylene reduction activity. From the above results, the author suggests that leghemoglobin might not be concerned with nodule respiration.

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Growth nodulation and root nodule nitrogen fixation of soybean plants treated by different methods of soil molding were investigated in a pot experiment along plant growth stages. By the standard method of soil molding (10 cm height) both growth and nitrogen accumulation of plants were respectively increased by 46% and 40% at 98 days after sowing. After the molding, many new nodules were formed on adventitious roots, and also number and weight of nodule of tap and lateral roots increased. The maximum nodule activity (acetylene reduction) per a plant reached higher level than that of unmolded plants, and its decline along growth stage was delayed. Soil molding with the supplemental Bradyrhizobium inoculation increased both the number and weight of nodule per a plant comparing to the plants treated with the standard molding. But the mean value of nodule size and weight of tap and lateral roots decreased, suggesting strong competition for photosynthate between nodules and roots and among nodules. A high soil molding method (15 cm height) enhanced growth of shoots, adventitious roots and nodules attached on the roots. Although the growth of tap and lateral roots and mass and activity of nodules formed on them seemed to be repressed, these were compensated by the adventitious roots and their nodules. Hence total nitrogen accumulation and acetylene reduction activity of the highly soil-molded plants was significantly higher than that of the plants standard soil molding.

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In a vegetable upland field of alluvial soil, an experiment was carried out for twelve plots in four mineral plot of applying nitrogen, phosphoric acid, potassium and lime, non-fertilizer plot, non-nitrogen plot of applying nitrogen, phosphoric acid, potassium and lime, non-fertilizer plot, non-nitrogen plot, non-phosphoric acid plot, non-potassium plot and non-lime plot with compost application of 20 Mg ha^<-1> or non-compost application during twenty-five years. Chemical and physical properties of soil were investigated in detail. 1. By continuous application of rice straw compost, content of total carbon and total nitrogen in soil increased not only in the Ap horizon but also in the AB and B horizon. Amounts of total carbon and total nitrogen that accumulated in soil for twenty-one years were 10.2 Mg ha^<-1> and 1.12 Mg ha^<-1>, respectively. 2. In Ap horizon of non-nitrogen plot, the pH was 7.3 and the base saturation percentage about 130%. On the other hand, in Ap horizon of non-lime plot, the pH was 4.2 and the base saturation percentage about 40%. 3. By continuous application of rice straw compost, physical property of soil in A pand AB horizon was obviously improved because of the increase of macro-pore rate and the decrease of penetration resistance value.

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Behavior of micronutrient elements around the soybean and barley roots were investigated using the rhizobox system. The rhizobox was divided into 15 soil compartments of 1 mm thickness. Soybean and barley seedlings grew in the root zone compartment. After two months of cultivation, all the compartments were separated from the rhizobox and the soil from each compartment was dried and analyzed for the element content. The results obtained wee : 1) Changes in pH were also observed in all the treatments and similar trends in pH change were observed whether the pH was measured in water or in 1N KCl suspension. The pH values across the rhizosphere or soybean and barley roots decreased by about 1.8-2.1 units. The significant decrease in pH of the soybean roots was observed 3-4 mm from the central compartment. But, the significant decrease in pH of the barley was observed in the 4-5 mm compartment. 2) Total Cu, Zn, Mn, Fe, Mg contents in each compartment showed little or no difference, but total Ca content increased slightly in the central compartment. 3) Most of soluble cations (Mn, Fe, Ca, Mg and Na) increased near the root, while the content of soluble K and NH_4 decreased. The solubilization of Fe by the bulk soil and by the rhizospheric soil was compared. The capacity of rhizospheric soil of Bride B 216 soybean to solubilize Fe and Mn in the soil was higher than that of Hawkeye, soybean.

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We investigated the relation of the amount of available N to soil biomass and organic material amended in order to examine the source of available N and process of accumulation of available N by the amendment of organic material. The soil samples used were collected from 3 upland fields (volcanic ash soil) amended with organic material continuously. Available N was measured by the incubation method (the aerobic incubation for 4 weeks at 30℃) using air-dried soil. High positive correlation was found between the amount of available N and soil biomass (biomass N and ATP) R^2 : 0.66-0.92). Available N was slao highly correlated with the amount of hot water-soluble organic substance C in soil (R^2 : 0.76-0.85). The amounts of soil biomass N (17.3-76.5 mg kg^<-1> dry soil) were 46-112% of that of available N (30-81 mg kg^<-1> dry soil) ; both values were almost identical. The amount of available N was highly correlated with the amount of easily decomposable fraction (hot water-soluble substance, carbo-hydrate, and crude protein) C in organic material amended (R^2 : 0.64-0.95). Based on these results, we concluded that biomass fraction in soil was a main source of available N, and the increase in soil biomass by the amendment of organic material resulted in the accumulation of available N in soil.

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Effects of NO_3-N in irrigation water and rice straw application on CH_4 emission from paddy fields were examined. 1) Soil Eh during the cultivation period was increased by rice straw application, while it was decreased by irrigation of high content of NO_3-N. 2) In the plot of rice straw the peak of the formation of acetic acid in soil solution was observed at the middle of June and the first part of August, while in the plot of rice straw and NO_3-N it was observed at the middle of June. It is considered that the difference of variation of the formation of acetic acid is due to the accelerated decomposition of organic materials caused by NO_3-N application. 3) CH_4 emission began to increase in parallel with the decrease of soil Eh and concentration of acetic acid in soil. In the presence of NO_3-N CH_4 flux was not proportional to the concentration of acetic that was considered to be the substrate of methane. These results indicate that CH_4 emission is inhibited by the presence of nitrate ion. These results confirmed that seasonal variation of CH_4 flux from paddy fields in closely related to soil Eh and acetic and in soil solution. It also suggests that agricultural practices such as irrigation and organic material application are important to reduce CH_4 emission from paddy fields.

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The treatment of buds of Kyoto and Pione (V. labrusca L.×V. vinifera L.) with ammonium nitrate and/or calcium cyanamide hastened the sprouting by 13 to 15 days. This hastening was induced within two days after treatment with the chemicals. Treatment with the chemicals slightly increased the nitrogen contents of the buds. In Delaware (V. labrusca L.×V. aestivalis×V. vinifera L.) ,hastening of sprouting by 5 to 6 days with ammonium nitrate treatment was also observed, particularly from the fifth to the seventh bud although this effect differed depending on the sites of chemical treatment. Using ^15N-labeled ammonium nitrate, a considerable incorporation of ^15N was transported from the site of treatment to other sits in the buds and later to the newly grown leaves.

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Treatment of buds of greenhouse-grown grapevines with ammonium nitrate on December or January or with calcium cyanamide on December hastened considerably the breaking of dormancy (sprouting). Using NH_4^<15>NO_3 or CaC^<15>N_2, the incorporation of ^<15>N into the buds was investigated. Further, the changes of amino acid concentrations in the buds treated with these chemicals were analyzed. NO_2-^<15>N and CN_2-^<15>N used on December were actively incorporated into amino acid and protein fractions. The treatment with NH_4NO_3 increased the concentrations of asparagine, glutamic acid, glutamine, hastidine and arginine in the buds. All amino acids, except aspartic acid were not increased during 8 days after treatment with CaCN_2 but thereafter, most of them were observed to increase. NO_3-^<15>N was transported to the newly grown buds but the transport of CN_2-^<15>N to this organ was small. NO_3-^<15>N used on January was also actively incorporated into the buds and the treatment with NH_4NO_3 greatly increased the concentrations of glutamine and alanine. The hastening of sprouting by 3 to 4 days due to treatment with ammonium nitrate was also observed in outdoor-grown grapevines, but the transport of NO_3^<15>N to the newly formed leaves was small.

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[in Japanese]

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