Methane emission rate was measured in 1993 using an automatic measuring systembuilt by the Institute of Atmospheric Physics,Chinese
Academy of Sciences,Methane e-mission factor is preliminary available for rice fields in South China region,which takesabout 20%of the total rice harvesting area in China. Then the methane emission factorsare already available in all the five major rice culture regions in China. The seasonal varia-tion of
methane emission rate depends mainly on the variation of air temperature and flood-ing condition. The afternoon peak mode is dominant for diurnal variation. The methane e-mission rate form this
experiment field is rather low,which may mainly due to the uniquecultivation system in Guangzhou that rice fields are normally kept free during winter timeand in the gap between early and late rice growing season. The low dosage or even withoutorganic manure may be another important reason.In our experiment the water floodingcondition was kept normal as in the local region so that the methane emission factor canrepresent more properly the real emission value from actual rice paddy fields。Annualmean temperature and soil organic matter are not the factors to explain the spatial varia-tion of methane emission rate from rice fields. The seasonal average of methane emissionrate was 0.5±0. 6 mg/m￣2·h.According to the available date set for methane emissionrate from various rice fields in China,and relevant area of rice cultivation , total methaneemission in Chinese rice paddies can be estimated 11.1(10.2～12.8)×10￣(12)g/a.