| Outline of Final Research Achievements |
In this project, mineral associated organic nitrogen, which is the largest terrestrial nitrogen pool, was investigated in terms of its accumulation form and microbial utilization. First, the influence of major soil forming factors on the distribution of active Al/Fe, which stabilize organic nitrogen, was clarified. Also, decreases in plant-derived organic compounds (e.g., lignin and polysaccharides) and increases in microbial-derived compounds (e.g., nitrogen containing organic compounds) were observed with increasing soil depth. The utilization of organic nitrogen was inhibited by the adsorption of organic nitrogen on active Al/Fe, but the effect was weakened by the organic matter coverage on active Al/Fe.
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