In a study on CH4 emission from flooded rice fields under irrigated co
nditions, fields planted with rice emitted more methane than unplanted
fields. The CH4 efflux in planted plots varied with the rice variety
and growth stage and ranged from 4 to 26 mg h(-1) m(-2). During the re
productive stage of the rice plants, CH4 emission was high and the oxi
dation power of rice roots, in terms of alpha-naphthylamine oxidation,
was very low. The CH4 emission reached a maximum at midday and declin
ed to minimum levels at midnight, irrespective of the rice variety. Th
e peak CH4 emission at midday was associated with higher solar radiati
on and higher soil/water temperature.