Stable carbon isotope fractionation, carbon flux partitioning and priming effects in anoxic soils during methanogenic degradation of straw and soil organic matter
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Author list: Conrad R., Klose M., Yuan Q., Lu Y., Chidthaisong A.
Publication year: 2012
Volume number: 49
Start page: 193
End page: 199
Number of pages: 7
ISSN: 0038-0717
eISSN: 0038-0717
Languages: English-Great Britain (EN-GB)
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Abstract
Straw amendment is a common practice for improving the fertility of rice field soils, but it also enhances production of the greenhouse gas methane. To quantify carbon flux partitioning and priming effects due to straw amendment, we measured δ 13C in CH 4 and CH 4 precursors produced in anoxic slurries of soil from Italy, China and Thailand after addition of straw from either rice (C3 plant) or maize plants (C4 plant), which have different δ 13C signatures. The δ 13C values of the CH 4, acetate and CO 2 produced were similar when expressed as the difference to the δ 13C value of the straw applied. These results indicated that the 13C-isotopic fractionation involved in methanogenic decomposition was similar for rice straw and maize straw. However, measurement of CH 4 produced in soil without or with straw showed that isotopic fractionation during methanogenic degradation of straw was smaller than during degradation of soil organic matter. Isotopic fractionation during hydrogenotrophic methanogenesis, measured in the presence of methyl fluoride, with straw was also smaller than with soil organic matter. The results show that 13C-isotopic analysis after application of rice straw and maize straw is a convenient approach for quantifying carbon flux partitioning during methanogenic degradation of straw and soil organic matter. In our experiments, straw degradation accounted for most of the CH 4 production and caused a negative priming effect on the methanogenic degradation of soil organic matter. © 2012 Elsevier Ltd.
Keywords
Flux partitioning, Maize straw, Methane production, Priming effect, Soil organic matter
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