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Mine soils are usually unfavorable for plant growth due to their acidic condition and low contents of organic matter and nutrients. To investigate the effect of organic material and lime on nitrogen processes in an acidic metal mine soil, we conducted an incubation experiment with treating livestock manure compost, dolomite, and oyster shell and measured soil pH, dehydrogenase activity, and concentration of soil inorganic N (NH₄ + and NO₃ - ). Compost increased not nly soil inorganic N concentration, but also soil pH from 4.4 to 4.8 and dehydrogenase activity from 2.4 to 3.9 μg TPF g -1 day -1 . Applying lime with compost significantly (P -1 day -1 ) compared with applying only compost. Here, the variation in dehydrogenase activity was significantly (P

To estimate potential use of fly ash in reducing and emission from soil, and fluxes from a paddy soil mixed with fly ash at different rate (w/w; 0, 5, and 10%) in the presence and absence of fertilizer N () addition were investigated in a laboratory incubation for 60 days under changing water regime from wetting to drying via transition. The mean flux during the entire incubation period ranged from 0.59 to with a lower rate in the soil treated with N fertilizer due to suppression of production by that acts as an electron acceptor, leading to decreases in electron availability for methanogen. Fly ash application reduced flux by 37.5 and 33.0% in soils without and with N addition, respectively, probably due to retardation of diffusion through soil pores by addition of fine-textured fly ash. In addition, as fly ash has a potential for removal via carbonation (formation of carbonate precipitates) that decreases availability that is a substrate for reduction reaction (one of generation pathways) is likely to be another mechanisms of flux reduction by fly ash. Meanwhile, the mean flux during the entire incubation period was between 0.64 and , and that of N treated soil was lower than that without N addition. Because N addition is likely to increase soil respiration, it is not straightforward to explain the results. However, it may be possible that our experiment did not account for the substantial amount of produced by heterotrophs that were activated by N addition in earlier period than the measurement was initiated. Fly ash application also lowered flux by up to 20% in the soil mixed with fly ash at 10% through removal by the carbonation. At the whole picture, fly ash application at 10% decreased global warming potential of emitted and by about 20%. Therefore, our results suggest that fly ash application can be a soil management practice to reduce green house gas emission from paddy soils. Further studies under field conditions with rice cultivation are necessary to verify our findings.

Decomposition of compost applied to soils is affected basically by its biological stability; but, many other chemical properties of the compost may also influence compost organic-C mineralization. This study was conducted to investigate the principal substrate quality factors of composts that determine C mineralization of compost with similar stability degree (SD). Three composts samples with similar SD but different chemical properties such as pH, C/N, K 2 SO 4 -extractable C, and molar ratio of NH 4 + to NO 3 - were mixed with an acid loamy soil and CO 2 emission was monitored during the laboratory incubation for 100 days. Temporal pattern of cumulative compost organic-C mineralization expressed as % of total organic C (C% TOC) followed double exponential first order kinetics model and the C% TOC ranged from 4.8 to 11.8% at the end of incubation. The pattern of C% TOC among the composts was not coincident with the SD pattern (40.1 to 58.6%) of the composts; e.g. compost with the lowest SD resulted in the least C% TOC and vice versa. This result indicates that SD of compost can not serve as a concrete predictor of compost mineralization as SD is subject not only to maturity of compost but also to characteristics of co-composting materials such as rice hull (low SD) and sawdust (high SD). Meanwhile, such pattern of C% TOC collaborated with pH, C/N, K 2 SO 4 -extractable C, and molar ratio of NH 4 + to NO 3 - of the composts that are regarded as chemical indices of the progress of composting. Therefore, for better prediction of compost mineralization in soils, it is necessary to consider both SD and other chemical indices (pH, C/N, and molar ratio of NH 4 + to NO 3 - ).