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

Straw incorporation is a common long-term practice to improve soil fertility in croplands worldwide. However, straw amendments often increase methane (CH) emissions from rice paddies, one of the main sources of anthropogenic CH. Intergovernmental Panel on Climate Change (IPCC) methodologies to estimate CH 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 CH emissions acclimate. Effects of long-term (>5 years) straw application on CH 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 CH oxidation rates through improved O transport into the rhizosphere. Our results suggest that recent model projections may have overestimated CH emissions from rice agriculture and that CH emission estimates can be improved by considering the duration of straw incorporation and other management practices.