Suppression of rice methane emission by sulfate deposition in simulated acid rain

Gauci, Vincent; Dise, Nancy B.; Howell, Graham and Jenkins, Meaghan E. (2008). Suppression of rice methane emission by sulfate deposition in simulated acid rain. Journal of Geophysical Research: Biogeosciences, 113(G00A07) pp. 1–6.

DOI: https://doi.org/10.1029/2007JG000501

Abstract

Sulfate in acid rain is known to suppress methane (CH₄) emissions from natural freshwater wetlands. Here we examine the possibility that CH₄ emissions from rice agriculture may be similarly affected by acid rain, a major and increasing pollution problem in Asia. Our findings suggest that acid rain rates of SO_2-4 deposition may help to reduce CH₄ emissions from rice agriculture. Emissions from rice plants treated with simulated acid rain at levels of SO_2-4 consistent with the range of deposition in Asia were reduced by 24% during the grain filling and ripening stage of the rice season which accounts for 50% of the overall CH₄ that is normally emitted in a rice season. A single application of SO_2-4 at a comparable level reduced CH₄ emission by 43%. We hypothesize that the reduction in CH₄ emission may be due to a combination of effects. The first mechanism is that the low rates of SO_2-4 may be sufficient to boost yields of rice and, in so doing, may cause a reduction in root exudates to the rhizosphere, a key substrate source for methanogenesis. Decreasing a major substrate source for methanogens is also likely to intensify competition with sulfate-reducing microorganisms for whom prior SO_2-4 limitation had been lifted by the simulated acid rain S deposition.

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