Masakazu Aoyama

Microbial Biomass Nitrogen and Mineralization-Immobilization Processes of Nitrogen in Soils Incubated with Various Organic Materials

Abstract The effects of the addition of organic materials on the change of the pattern of microbial biomass N in soils were assessed in relation to the mineralization — immobilization processes of N. Two types of field moist soils (Udifluvent and Melanudand) amended with chicken manure, clover leaves, farmyard manure, bark compost and rice straw were incubated for 16 weeks at 25°C, and the amounts of biomass N and inorganic N were measured periodically. The chloroform fumigation-extraction method was used for measuring the soil microbial biomass N. Chicken manure was rapidly mineralized from the onset of incubation and did not result in an appreciable increase of the amount of microbial biomass N (<4.0% of the added organic N). Clover leaves showed a lag period of 2 weeks before active N mineralization commenced and the amount of microbial biomass N increased during the lag period, reaching a value of 13.6% of the added organic N, while the amount of biomass N decreased rapidly. On the other hand, the add...

Factors Affecting Microbial Biomass and Dehydrogenase Activity in Apple Orchard Soils with Heavy Metal Accumulation

Abstract The size of the microbial biomass and dehydrogenase activity were measured in air-dried and rewetted apple orchard surface soils with accumulation of Cu, Pb, and As due to the application of Bordeaux mixtures and lead arsenate. The largest amounts of total Cu, Pb, and As found in the soils used were 1,108, 1,271, and 209 mg kg-1 soil, respectively. The amounts of 0.1 M HCl-extractable heavy metals were strongly correlated with the total amounts, while those of 0.1 M CaCl2-extractable heavy metals, except for As, increased significantly with decreasing soil pH. The amounts of microbial biomass C and N, expressed on a soil organic C and total N basis, respectively, were each negatively correlated with the amounts of total and 0.1 M HCl-extractable Cu. On the other hand, the dehydrogenase activity was not affected by the amounts of total and 0.1 M HCl-extractable heavy metals, and was negatively correlated with the amount of 0.1 M CaCl2-extractable Cu and positively with the soil pH. Higher signific...

Effects of heavy metal accumulation in apple orchard soils on microbial biomass and microbial activities

Abstract The effects of heavy metals (Cu, Pb, and As) accumulated in apple orchard surface soils on the microbial biomass, dehydrogenase activity, and soil respiration were investigated. The largest concentrations of total Cu, Pb, and As found in the soils used were 1,010, 926, and 166 mg kg−1 soil, respectively. The amounts of microbial biomass C and N, expressed on a soil organic C and soil total N basis, respectively, were each negatively correlated with the amounts of total, 0.1 M HCI-extractable, and 0.1 M CaCl2-extractable Cu as logarithmic functions, the correlation coefficient being lowest for the 0.1 M CaCl2extractable Cu. Nevertheless, they were not correlated with the soil pH which was controlling the solubility of Cu in 0.1 M CaCl2. The dehydrogenase activity expressed per unit of soil organic C was also negatively correlated with the amounts of total, 0.1 M HCI-extractable Cu, and 0.1 M CaCl2-extractable Cu as logarithmic functions. However, the correlation coefficient was highest for the 0.1...

Fractionation of water-soluble organic substances formed during plant residue decomposition and high performance size exclusion chromatography of the fractions

Abstract Plant residue-sand mixtures were incubated for 28 d at 25°C under upland conditions, and water extracts were obtained periodically. Three kinds of plant residues (rapeseed meal, orchard grass shoots, and rice straw) were used and mixed with sand at a rate of 20 g kg-1. The water extracts were fractionated into three fractions, i.e., humic acids (HAs), polyvinylpyrrolidone (PVP)-adsorbed fulvic acids (FAs), and PVP-non-adsorbed FAs. High performance size exclusion chromatography (HPSEC) on an Asahipack GS-320H column was performed on the water extracts and the fractions. The amount of organic C in the extract tended to decrease with time, and at the same time the formation of water-soluble humic substances (HS) was observed by HPSEC. The molecular weight (MW) of HS at peak maximum varied with the plant residues used. A large proportion of the organic substances contained in the plant residues belonged to the PVP-non-adsorbed FA fraction, and this fraction was considerably reduced by the incubation...

Influence of biochar addition on methane metabolism during thermophilic phase of composting.

CH4 is known to be generated during the most active phase of composting, even in well‐managed composting piles. In this manuscript, we studied the influence of biochar on the CH4 metabolism during composting of cattle manure and local organic wastes. We evaluated the presence of methanogens and methanotrophs in the composting piles quantified by the level of mcrA encoding methyl coenzyme M reductase alpha subunit and pmoA encoding particulate methane monooxygenase. A decrease of methanogens (mcrA) and an increase of methanotrophs (pmoA) were measured in the composting mixture containing biochar during the most active phase of composting. During the thermophilic phase, the mcrA/pmoA ratios obtained in the composting piles with biochar were twofold lower than in the pile without biochar.

Effects of copper on the decomposition of plant residues, microbial biomass, and β-glucosidase activity in soils

Abstract Two types of soils (Brown Lowland soil and Ando soil), which were artificially enriched with different amounts of Cu, were incubated with or without pulverized orchard grass for 12 weeks at 25°C. For both soils with and without orchard grass amendment, the amount of CO2 evolved over the 12-week period of incubation decreased by the enrichment with Cu at a concentration exceeding 1,000 mg kg−1 soil. The decrease of the mineralization of added orchard grass in the Cu-enriched soil was conspicuous especially during the initial period of incubation. The amount of microbial biomass C at the end of the incubation was significantly reduced by the Cu enrichment regardless of the amendment with orchard grass. The relative decrease of the soil microbial biomass was much greater than that of the soil respiration. The amount of biomass C was negatively correlated with the amount of 0.1 M CaCl2-extractable Cu as a logarithmic function. On the other hand, the β-glucosidase activity at the end of the incubation...

Properties of fine and water-soluble fractions of several composts. I. Micromorphology, elemental composition and nitrogen mineralization of fractions

Abstract Organic forms of nitrogen, neutral sugars, and muramic acid, a constituent of bacterial cell walls, were analyzed in particle size fractions (F1, sedimented for 16 h at 4°C; F2, sedimented by centrifugation at 10,000 × g; F3, sedimented by centrifugation at 100,000 × g; F4, supernatant of F3) separated from four composts. Amino acid-N and ammonium-N were the predominant constituents of hydrolyzable organic nitrogen in all the fractions and amino sugar-N accounted for only a small proportion. The percentage of amino acid-N in organic nitrogen was higher than that of ammonium-N for fractions F1-F3, the reverse being true for fraction F4. The amino sugar-N content was significantly correlated with the amount of mineralizable organic N in fraction F4. The neutral sugars released by acid hydrolysis accounted for 10-35% of the dry matter in fraction Fl, but only for 2-10% in fractions F2-F4. Hexoses were the predominant sugars in all the fractions and glucose generally represented the largest portion o...

Comparison of the effects of Cu, Pb, and As on plant residue decomposition, microbial biomass, and soil respiration

Abstract Comparisons were made among the effects of Cu, Pb, and As on the plant residue decomposition, microbial biomass, and soil respiration using soils artificially enriched with Cu, Pb, and As. A total of eight metal treatments, consisting of a control, single metal treatments (10 mmol Cu kg−1, 20 mmol Cu kg−1, 10 mmol Pb kg−1, and 10 mmol As kg−1), and combined metal treatments (5 mmol Cu kg−1+2.5 mmol Pb kg−1+1 mmol As kg−1, 10 mmol Cu kg−1+5 mmol Pb kg−1 + 2 mmol As kg−1, and 20 mmol Cu kg−1 + 10 mmol Pb kg−1 +4 mmol As kg−1) were prepared. The inhibition of orchard grass decomposition was estimated by the difference in the contents of organic C and total N of soils treated with individual metals with and without orchard grass amendment following incubation under field conditions for 3 years. In the metal concentration range studied, Cu inhi~ited severely the orchard grass decomposition, Pb slightly inhibited it, while As had no notable effect on it. The amounts of microbial biomass C and N and the...

Effects of copper on the metabolism of 14C-labeled glucose in soil in relation to amendment with organic materials

Abstract The effects of Cu on the mineralization of 14C-labeled glucose in soil and the incorporation of 14C into the soil microbial biomass were investigated in a laboratory experiment in relation to the amendment with organic materials. Samples from a Brown Lowland soil (Udifluvent), which was amended with farmyard manure or orchard grass at the rate of 20 g kg-1 soil and/or enriched with 2,000 mg kg-1 soil of Cu, were incubated for 14 weeks under field conditions. The amounts of microbial biomass C and biomass ninhydrin-N in the field-incubated soils were significantly reduced by the addition of Cu regardless of the amendment with organic materials. The field-incubated soils to which 14C-labeled glucose was added were incubated for 28 d at 25°C in the laboratory. While the Cu added to soil did not affect appreciably the mineralization of 14C-labeled glucose, the amendment with organic materials affected considerably the pattern of mineralization. On the other hand, the incorporation of 14C into the soi...

Use of high performance size exclusion chromatography to monitor the dynamics of water-soluble organic substances during the decomposition of plant residues in soil

Abstract Soils amended with plant residues (20 g kg-1 soil) were incubated for 56 d at 25°C under upland conditions, and water extracts were obtained periodically. The decomposition process was monitored using high performance size exclusion chromatography (Asahipack GS-220M column) for the extracts detected by absorbance at 280 nm. Two types of soils (Udifluvent and Melanudand) and three kinds of plant residues (rapeseed meal, orchard grass shoots, and rice straw) were used for the experiment. The rates of decomposition were in the order of rapeseed meal > orchard grass shoots > rice straw, and the decomposition of rice straw caused the immobilization of inorganic N throughout the incubation period. In all the treatments, the amount of water-soluble organic C decreased sharply during the early period of incubation. The amount of organic substances contained in the plant residues rapidly disappeared from the water extract, and simultaneous formation of water-soluble organic substances was observed by high...