Seasonal variation of methane flux from a California rice paddy

To allow increased understanding of the global budget of atmospheric methane, individual methane sources require investigation. We have measured methane emissions from a California rice paddy during the entire 1982 growing season. A very strong seasonal dependence was observed. Methane emissions were highest in the last 2–3 weeks before harvest; daily emissions reached 5 g CH 4 /m 2 . Over the 100‐day season, daily emissions averaged about 0.25 g CH 4 /m 2 , higher than our previously reported values. Attempts to estimate global rice paddy emissions must recognize the possibility of seasonal variations. Soil temperature at 10‐cm depth correlated poorly with our measured fluxes; soil redox potential was a more reliable indicator.