Water Management Influencing Methane and Nitrous Oxide Emissions from Rice Field in Relation to Soil Redox and Microbial Community

Abstract

Methane (CH₄) and nitrous oxide (N₂O) emissions from an irrigated rice field under continuous flooding and intermittent irrigation water management practices in northern China were measured in situ by the static chamber technique during May to October in 2000. The intermittent irrigation reduced total growing‐season CH₄ emission by 24.22% but increased N₂O emission by 23.72%, when compared with the continuous flooding. Soil Eh and four related bacterial groups were also measured to clarify their effects on gaseous emissions. Three ranges of soil redox potential were related to gas emissions: below −100 mV with vigorous CH₄ emission, above +100 mV with significant N₂O emission, and +100 to −100 mV with little CH₄ and N₂O emissions. Intermittently draining the field increased soil oxidation, with a decrease in CH₄ emission and an increase in N₂O emission. In general the mid‐season drainage slightly increased the populations of methanotrophs, nitrifiers, and denitrifiers but decreased that of methanogens.

Keywords:

• CH₄ emission
• continuous flooding
• Eh
• intermittent irrigation
• microbial population
• N₂O emission

Acknowledgments

This work was supported by the Knowledge Innovation of Chinese Academy of Sciences (grant no. KZCX1‐SW‐01) and the U.S. Department of Agriculture, National Research Initiative Competitive Grants Program (2001‐35107‐09941). The authors thank Ronald DeLaune for helpful comments on the manuscript.