Estimation of seasonal changes in methane oxidation in paddy soil
2009
Muramatsu, Y.(Chiba Univ. (Japan)) | Inubushi, K.
The potential methane production and oxidation activities of a paddy soil were estimated over a growing season. Anaerobic incubation of a paddy soil in an Erlenmeyer flask generated methane at a rate of 5.8 micro gC/g soil/day. Methane oxidation under a gas phase of CH4:air (1:1) was higher by two orders of magnitude ranging from 100 to 400 micro gC/g soil/day. The significant difference in the production and oxidation potential suggests that methane emission from paddy soils could effectively be mitigated if certain conditions for methane oxidation such as presence of oxygen are met in the soil. In situ methane oxidation was computed by measuring methane production, emission and methane retained in the soil over a growing season. Without rice plant, 87% of the methane produced was oxidized in the soil. As a result, emission to the atmosphere was 10% of total production. At the latter stage, the production rate of methane balanced with the oxidation rate. It was assumed that methane was rapidly oxidized upon production in the soil during the period. With the rice plant, methane emission accounted for 56% of the total methane production. Methane oxidation in the soil, on the other hand, fell to 41% of the total production. In the active tillering stage of rice plant, the oxidation rate was equivalent to 80% of the methane production rate. Analysis of gas retained in the soil in the same period indicated higher oxygen content which would accelerate methanotrophic activity in the rhizosphere. This also contributes to temporal decline of the rate of methane emission in the same period resulting to its apparent seasonal pattern. The inherent nature of rhizoshpere having oxidizing capacity may serve as basis for designing cost effective control measures for methane emission applicable to developing countries in South East Asia.
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