Seasonal variations of CH₄ flux, soil Eh and soil temperature were determined in paddy fields at Phitsanulok, San Pa Thong and Phrae for the major and the second rice croppings*. The average values of the CH₄, fluxes measured for the major rice at Phitsanulok, San Pa Thong and Phrae were 7.4, 16.1 and 22.2 mg m^-2 h^-1 respectively, and for the second rice 6.6, 8.8 and 15.9 mg m^-2 h^-1, respectively. The CH₄ emission from Phrae paddy field in the second rice was higher than that of San Pa Thong due to the high content of fresh organic materials and abundant water supply.
The estimated seasonal emissions for the major rice at Phitsanulok, San Pa Thong and Phrae were 17.4, 39.8 and 68.2 gm^-2, respectively, and for the second rice 17.9, 21.3 and 48.5 g m^-2, respectively. The high estimated seasonal emission of CH₄, at Phrae was attributed to the longer duration of the flooding period and higher CH₄, flux values than at the other two sites.