Mechanisms and suppression of the accumulation of volatile fatty acids and the production of methane in submerged paddy soil
2000
Nozoe, T. (Tohoku National Agricultural Experiment Station, Morioka (Japan))
In submerged paddy soil, volatile fatty acids (VFAs) are produced under reduced conditions. The accumulation of VFAs has been one of the factors responsible for rice growth inhibition. In paddy soil, VFAs consist mainly of acetate followed by propionate and n-butyrate, and most of these acids are decomposed to methane and/or carbon dioxide. Methane is recognized as one of the most important gases associated with the greenhouse effect. In this paper, laboratory studies were conducted to analyze firstly the characteristics of the accumulation of VFAs, subsequently the mechanisms of the decomposition of VFAs, and finally the effect of the addition of iron or sulfate materials on the decomposition of VFAs and the production of methane. 1) The amounts of VFAs increased by the addition of rice straw. When the soil was kept under an oxidative condition before irrigation, the amounts of VFAs increased after irrigation. 2) Methane was produced firstly from hydrogen and carbon dioxide, and subsequently from acetate. Therefore, the presence of hydrogen delayed the decomposition of acetate. 3) Propionate was decomposed to acetate along with sulfate reduction. n-Butyric acid was decomposed to acetate along with Fe (III) reduction. 4) The addition of amorphous Fe (III) oxide or sulfate suppressed the accumulation of VFAs as well as the production of methane
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