| Abstract: | Methane (CH4) emission from flooded rice fields was measured hourly over 24 h for rice (Oryza sativa L.) seasons in 2008 and 2009. The objectives of this study were to identify typical diel variation in CH4 emission and to estimate the best time of day for optimum extrapolation of daily CH4 emission. Our results showed distinct diel variation in CH4 emission, which exhibited a maximum at 14:00–15:00 and a minimum at midnight. About 5.2–5.6% of total CH4 emitted per day (110–160 mg CH4 m?2 d?1) was released at 14:00–15:00. The diel pattern of CH4 emission resembled that of air temperature (Ta). The Ta coupled with solar radiation could cause a difference in partial pressure of CH4 (DPPC) through the gas conduit of the plant. The best extrapolation of daily CH4 emission was achieved with data observed at 10:00–11:00. We concluded that DPPC-induced CH4 emission is an important mechanism causing diel variation. |
