Acclimation of methane emissions from rice paddy fields to straw addition.

Abstract

Straw incorporation is a common long-term practice to improve soil fertility in croplands worldwide. However, straw amendments often increase methane (CH₄) emissions from rice paddies, one of the main sources of anthropogenic CH₄. Intergovernmental Panel on Climate Change (IPCC) methodologies to estimate CH₄ emissions from rice agriculture assume that the effect of straw addition remains constant over time. Here, we show through a series of experiments and meta-analysis that these CH₄ emissions acclimate. Effects of long-term (>5 years) straw application on CH₄ emissions were, on average, 48% lower than IPCC estimates. Long-term straw incorporation increased soil methanotrophic abundance and rice root size, suggesting an increase in CH₄ oxidation rates through improved O₂ transport into the rhizosphere. Our results suggest that recent model projections may have overestimated CH₄ emissions from rice agriculture and that CH₄ emission estimates can be improved by considering the duration of straw incorporation and other management practices.