METHANE EMISSION FROM RICE PADDY FIELDS IN THE CENTRAL PLAIN OF THAILAND

Emission rates of CH, from rice paddy fields were measured in the central plain of Thailand. The measurements taken monthly during the cultivation periods showed a significant difference in CH4 emission rates among three sites. One paddy field, in Suphan Buri, showed a relatively high emission of CH4, with average fluxes of 19.5-32.2 mg m-2 h-1. The average fluxes from the other two paddy fields, in Khlong Luang and Chai Nat, were 3.8 and 1.6 Mg M-2 h-1, respectively, being one order of magnitude lower than those from Suphan Buri. The low emission of CH4 at the two sites was attributed to the high concentration of sulfate in soil or the high soil Eh due to the lower abundance of the reducing capacity in relation to the oxidizing capacity of soil. The results suggest that it is essential to provide a data base of soil characteristics, such as soil type and chemical composition of soil affecting the oxidation-reduction process, as well as conduct extensive field measurements in various rice growing countries to evaluate the global emission rates of CH4 from rice paddy fields.