Yutaka Oba

Effect of fungal to bacterial biomass ratio on the relationship between CO2 evolution and total soil microbial biomass

The relationship between the fungal: bacterial biomass ratio and the metabolic quotient (qCO2) was studied in three different soils. In addition, the effect of the fungal: bacterial biomass ratio on the relationship between CO2 evolution and the size of the soil microbial biomass was examined. Soil samples were collected from three experimental fields amended with various organic materials (Yatsugatake, Ibaraki, and Tochigi fields). The range of the fungal:bacterial biomass ratio in the Yatsugatake and Ibaraki fields was small (1.54–2.24 and 1.11–1.71, respectively), but it was large in the Tochigi field (1.18–3.75). We found a high negative correlation between this ratio and the metabolic quotient (qCO2=2.10−0.361 (fungal:bacterial biomass ratio), R=−0.851, P<0.01) in the Tochigi field. Therefore, we suggest tha qCO2 decreases with an increase in the fungal:bacterial biomass ratio, which may be due to a higher efficiency of substrate C use by fungal flora in comparison with bacterial flora. In the Yatsugatake and Ibaraki fields, there was a high positive correlation between CO2 evolution and total microbial biomass. In contrast, no correlation was observed between these two parameters in the Tochigi field, probably reflecting the wide range of values for the fungal:bacterial biomass ratio. From the results obtained, we suggest that the fungal: bacterial biomass ratio is an important factor regulating the relationship between CO2 evolution and the size of the microbial biomass.

Relationship between the amount of organic material applied and soil biomass content

Abstract The relationship between the amount of organic material applied and soil biomass content was examined in soils amended with various organic materials in 4 upland experimental fields. The values of the soil biomass measured by the direct microscopic method (DMM), ATP content, and soil respiration rate in the soil amended with organic material were greater than those in the soil amended with inorganic fertilizer in all the fields. Soil biomass measured by the DMM and ATP content were highly correlated with the sum of the amount of hot water-soluble organic substance, carbohydrate, and crude protein components in the organic material applied in all the fields. Soil respiration rate was also highly correlated with the sum of the amount of these components applied in the 3 fields. These results suggest that hot water-soluble organic substance, carbohydrate, and crude protein components in organic material are closely related to the increase of the soil biomass. The difference in the soil biomass C con...

Characteristics of Soil Humic Substances Fractionated in Relation to Particle Weight : VI. Particle Weight Distribution, Optical Properties, and Infrared Absorption Spectra of Fractions of Humic Acids with Different Particle Weights

Abstract Particle weight distribution of humic acids (A, B, Rp, Po, and P types) was estimated by applying the successive gel filtration method using five grades of Sephadex, and the fractions with different particle weights were characterized by analyzing their optical properties and infrared absorption (I.R.) spectra. With the progress of humification, the large particle components and polydis-persion of the particle weights decreased. The degree of humification in the A and B types was maximum for the middle particle weight fraction, while in the Rp, Po, and P types it was higher In the fractions with smaller particle weight. The differences in the optical properties among the fractions were more pronounced when the humification degree Increased. I.R. spectra of the fractions showed differences in Intensities at some bands; near 3,300, 2,920-2,840, 1,720, near 1,650, 1,600, near 1,520, 1,460-1,360, 1,180-1,030 cm-1 and a few specific bands. The large particle weight fractions contained colorless compon...

Clay Mineralogical Analysis Using the <0.05-mm Fraction for Forensic Science Investigation—Its Application to Volcanic Ash Soils and Yellow-Brown Forest Soils

Clay mineralogical analysis is conducted with a fraction size of less than 0.05 mm in diameter (

Rapid Clay Mineralogical Analysis for Forensic Science Investigation—Clay Mineralogy Over the Short Distances

Rapid clay mineralogical analysis using a particle size fraction less than 0.05 mm without extraction of a clay fraction (

Decomposition of sewage sludge in soil

Abstract Activated sludge from a sewage disposal plant was labeled with 15N in the laboratory. The labeled sludge (dewatered cake) was then incubated under aerobic conditions for 30 days with four kinds of cultivated soils: volcanic ash soil, red-yellow soil, paddy soil, and sandy dune soil. The nitrogen mineralization of the soil organic matter was remarkable only in the case of the paddy soil. In this soil, a priming effect caused by the addition of the sludge was observed. After 30 days of incubation, the 15N organic fractions remaining in the red-yellow soil were determined. It was found that the amino acid and the unidentified fractions in the hydrolyzable nitrogen forms of the sludge contributed mainly to the amount of nitrogen mineralized. Finally, using sludges which originated from the same organic matter source, the lnftuence of a generally-used inorganic coagulator Oime and ferric chloride) of sludge on the nitrogen cycle was clarified. This coagulator caused a reduction in the amount of inorpn...