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Abstract
Four composts, prepared from cow feces (A), city refuse (B), cow feces plus saw-dust (C), and swine feces plus saw-dust (D), were each separated into four fractions. These consisted of the coarse fraction, Fl (sedimented at 4°C), the fine fractions, F2 (sedimented by centrifugation at 10,000×g), and F3 (sedimented by centrifugation at l00,000×g), and the water-soluble fraction, F4 (supernatant of F3). Electronmicroscopic observation, elemental analysis, and incubation study for estimating the mineralizable organic nitrogen were carried out on each fraction. The results obtained are as follows:
1) By electronmicroscopic observation, bacterial cells, their cell walls or cell membranes, and amorphous substances were identified in fraction F2; membranous and filamentous materials probably derived from bacterial cells, and amorphous substances were revealed in both fractions F3 and F4. | |||||
2) Nitrogen was concentrated in fractions F2–F4, and the C/N ratios of the fractions F2–F4 obtained from composts A and B, which did not contain saw-dust, were low, whereas those obtained from composts C and D, which contained saw-dust increased with decreasing particle size. | |||||
3) In the H/C–O/C diagram, plots of the fine fractions F2 and F3 of each compost were located between those of the bacterial cell fractions and humic substances, while the plot of the water-soluble fraction F4 of each compost was located between those of Rp type humic acids and fulvic acids. | |||||
4) The percentage mineralization of organic nitrogen was relatively higher in fractions F2–F4 than in fraction F1, regardless of the C/N ratios. | |||||
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