Shigekata Yoshida

Enhancement of the Effectiveness of Indigenous Arbuscular Mycorrhizal Fungi by Inorganic Soil Amendments

Abstract The influence of inorganic soil amendments on the effectiveness of indigenous arbuscular mycorrhizal (AM) fungi was investigated in pot experiments. Intact or ground perlite, Kanumatsuchi (volcanic ash soil), vermiculite, or rice-hull charcoal was mixed with uncultivated soil in which Glomus sp. was dominant, and marigold (Tagetes patula L.) was sown to the soil mixtures. AM colonization of the host roots increased by the incorporation of ground materials but not by that of intact materials. The growth promotive effect of the indigenous fungi on the host was enhanced by both the intact and ground materials. The inorganic materials improved the soil physical properties: the intact materials increased the gaseous phase of the media and the ground materials increased the aqueous phase. It was suggested that the inorganic soil amendments might not only provide a less-competitive habitat for the fungi but also improve the physical environment.

Chemical and microbial properties of various compost products

Abstract Chemical and microbial characterizations were carried out for forty-four compost products, whose raw materials were classified into seven categories: wood, coffee ground, grass, buckwheat shells, animal manure, food waste, and others. Microbial community structure in the composts was examined by quinone profile analysis. Values of the chemical and microbial properties varied considerably as follows: moisture content 3.1–82.7%, pH 4.38–9.44, electric conductivity (EC) 0.12–17.08 mS cm−1, total carbon (TC) content 16.9–51.0%, total nitrogen (TN) content 0.61–9.83%, C / N ratio 5.2–53.1, ash content 4.2–63.2%, total quinone (TQ) content 0.0–215.2 µmol kg−1 dry sample, and value of quinone diversity (DQ) index 0.0–20.8. The wide range in the values expressed the diversity of the chemical and microbial properties of various compost products. The chemical properties were related to the raw materials while the microbial properties tended to be less related. Total menaquinone contents were higher than the total ubiquinone contents in most of the composts. The common major quinone species was menaquinone-7, indicating the predominance of Bacillus. The average mole fractions of menaquinones with partially saturated and long side-chains accounted for about 37% of the TQ content, indicating the proliferation of Actinobacteria. Multiple regression analysis suggested that microbial properties were significantly related to the moisture content, pH, and C / N ratio of the compost products. The DQ increased with the increase of the quinone contents and became stable at the value of about 16.5 in the composts with more than 50 nmol kg−1 of quinones. At the same time these values were observed only in the composts with C / N ratios lower than 20.

Low nitrogen fixation of common bean (phaseolus vulgaris L.)

Abstract Nitrogen fixation activity in legumes varies among species and common bean (Phaseolus vulgaris L.) is known to exhibit a lower ability to fix nitrogen than other legumes such as soybean (LaRue and Patterson 1981; Nishimune et al. 1983). Therefore, the dependence of common bean on nitrogen fertilizer is considerably higher than that of soybean (Matsushiro 1971). At least, three factors may contribute to the low nitrogen fixation observed in common bean: (1) delay of nodule appearance on root system, (2) insufficient nodule mass on root system, and (3) ineffectiveness of nodules formed on root system. In this paper, the nodulation and nitrogen fixation of common bean and soybean were investigated using the root-box-culture technique.

Changes in the community structure of aquatic organisms after midseason drainage in the floodwater of Japanese paddy fields

Abstract The purpose of this study was to analyze the seasonal variations in diversity and community structure of aquatic organisms in paddy fields. The varieties and the number of aquatic organisms ranging in size from 30 mm to 2 cm in the floodwater of five Japanese paddy fields were surveyed every 10 d during the growth period of rice plant. Aquatic organisms were classified mainly at the order level. As a result, forty four varieties (classified groups) of aquatic organisms were detected in the present survey. The number of varieties significantly increased and the community structure of the aquatic organisms changed after midseason drainage. Principal component analysis showed that three varieties (Volvocida, Oligotrichida, Cladocera) and four varieties (Lemnaceae, Pharyngophorida, Chaetonotida, Turbellaria) characterized the community structure of aquatic organisms before and after midseason drainage, respectively.

Temporal changes in humic acids in cultivated soils with continuous manure application

Abstract Although the application of manure to upland fields is believed to induce changes in the quality of humic substances in soil as well as the quantity, the direction and extent of these changes have not been elucidated. To understand temporal variations in humic acids, periodically collected soil samples from two fields, a Typic Hapludult (Togo) and a Pachic Melanudand (Kuriyagawa), with cattle manure and chemical fertilizer (CF) were examined. The content and degree of humification (darkening) of the humic acids were distinctly greater in Kuriyagawa than in Togo soil. Corresponding to the difference in the degree of humification, molecular size distribution, elemental composition, infrared (IR) spectra, and 13C cross polarization/magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectra of humic acids differed between the two soils. Manure application at 40 Mg ha−1 year−1 for 16 years (Togo) and at 80 or 160 Mg ha−1 year−1 for 19 years (Kuriyagawa) resulted in greater humic acid content compared with plots with CF only because of its increase in the manured plots and/or decrease in the CF plots. Manure application at an extremely high rate (160 Mg ha−1 year−1) resulted in higher H content and greater signal intensities of alkyl C, O-alkyl C and amide C=O in the 13C CPMAS NMR and/or IR spectra. Although humic acids with larger molecule sizes increased in all the manured plots, differences between the humic acids from the plots with and without manure applied at practical levels in the elemental and spectroscopic analyses were small or scarce. These results were considered to be because of the similarity between the indigenous soil humic acids and the manure-derived ones in Togo soil (a low degree of humification) and because of the abundance of highly-humified humic acids in Kuriyagawa soil.

STEM NODULATION ON Aeschynomene indica PLANTS BY ISOLATED RHIZOBIA

Stem nodulation on Aeschynomene indica was first reported 30 years ago (l). The nodule have been observed only on the submerged lower parts of stems. Recently, this species has been found to bear nodules on the aerial parts of stems under natural conditions, which fix dinitrogen as indicated by their acetylene reducing activities (7). EAGLESHAM and SZALAY (3) reported more recently that a single inoculation of the stems of Aeschynomene plants with a rhizobial strain isolated from a submerged stem nodule on an A. indica induced the formation of green N2-fixing aerial stem nodules. However, the mechanism of this stem nodulation had remained unclear. The objectives of this study were: (a) to compare the ability of stem nodulation between rhizobial strains isolated from root and stem nodules; and (b) to examine the effects of sucrose and yeast extract on stem nodulation.

Improvement of Leonard jar assembly for screening of effective rhizobium

Abstract Leonard jar assembly (1) which is a useful apparatus for aseptic culture of the underground part of plant, has been used for the study of legume-rhizobium symbiosis. However, the assembly has some disadvantages requiring improvement (2-4). One of the disadvantages is the tendency to restrict root growth in the growth bottle, which hinders nodule formation and nitrogen fixation of leguminous plants. In this paper, an improvement of Leonard jar assembly is reported and also nodulation and nitrogen fixation of mungbean grown with the improved jar assembly were investigated in relation to the effectiveness of rhizobium inoculation.

Fine structure of root nodules of Aeschynomene indica L.

Fine structure of nitrogen-fixing root nodules of Aeschynomene indica L. was investigated by electron microscopy since these nodules arise through intercellular infection and this plant species bears nitrogen-fixing aerial stem nodules. Electron micrographs showed that cells in the bacteroid region were completely packed with spherical bacteroids (o2–3 µm) which were estimated to have multiplied by single binary fission. Bacteroid-filled cells included central large nuclei, several mitochondria and a few plastids within the electron dense cytoplasmic matrix. Cortical cells directly adjacent to the bacterial region were vacuolated and contained rough endoplasmic reticulum, mitochondria and plastids embedding starch granules in their electron dense cytoplasm located at the periphery. Electron micrographs of bacteroids at a high resolution revealed that the membrane surrounding the bacteroid cytoplasm had a double layer structure and that a periplasmic space existed between the layers. Inside the bacteroid, ...

Growth, nodulation, and nitrogen fixation of soybean plants with seeds treated with kasugamycin.

Abstract For the purpose of using kasugamycin resistant rhizobium as an inoculum, the effects of kasugamycin on growth, nodulation, and nitrogen fixation of soybean were investigated. Differences in the kasugamycin tolerance among rhizobial strains were also studied. Seed treatment with kasugamycin at 2,500 ppm brought about a change of the leaf shape and also induced the growth suppression of plants semi-aseptically cultured in vermiculite sterilized by autoclave. On the contrary, the growth of the plants cultured in soil was not appreciably suppressed by the kasugamycin treatment. However, kasugamycin markedly affected the nodulation process. That is, the number of nodules formed on the treated plants (more than 500 ppm kasugamycin) decreased by about 50% of that of the non-treated plants. However kasugamycin did not affect significantly the nitrogen fixation of soybean plants. Nineteen Bradyrhizobium japonicum strains out of the 21 strains tested were sensitive to 1,000 ppm kasugamycin. On the contrary...

Difference in Phosphorus Response among Tropical Green Manure Legumes Grown under Limed and Unlimed Soil Conditions

Abstract Two pot experiments were conducted to investigate the effect of phosphorus fertilization on the growth of some tropical green manure legumes cultivated under limed and unlimed soil conditions. The species used were Cassia occidentalis, Cassia tora, Crotalaria juncea, Glycine max, Sesbania cannabina, and Seshania rostrata. The species differed in their response to lime application. Liming increased the dry matter yield of Cro. juncea, G. max, S. cannabina, and S. rostrata while it decreased the dry matter yield of Cas. occidentalis and Cas. tora. Liming decreased the concentrations of P, Fe, Mn, and Zn while it increased the concentration of Ca in all species. The Mg concentration decreased in Cas. occidentalis and Cas. tora by liming while it increased in other species. The cause of the growth depression resulting from liming depended on the species. The growth reduction in Cas. occidentalis, Cas. tora, and Cro. juncea was due to the low concentration of P in the plant tissues. The deiciency in Z...