Estimate of methane (CH4) and carbon dioxide (CO2) emissions from a rain-fed rice field by eddy covariance technique

Climate change induced by emissions of greenhouse gases from sources associated with human activities has caused devastating impacts and is regarded as one of the most challenging threats to humankind. Quantifying the amounts of greenhouse gas emissions is an important first step towards mitigation. This study aimed to estimate the emissions of methane (CH4) and carbon dioxide (CO2) from one of the most important emission sources in Thailand, which is rice cultivation, by using the eddy covariance technique. It was found that the average CH4 emission throughout the year was 0.06 mg CH4/m2 . The annual emission of approximately 1.37 kg CH4/ha/d was estimated. This was comparable to that provided by the IPCC for the baseline emission (i.e., 1.3 kg CH4/ha/d). On the other hand, results reveal that the rice field acted as a net carbon sink, with an annual CO2 uptake of -72.60 mg CO2/m2 /y, equivalent to 8.41 tons C/ha/y. During the growing season, an amount of CO2 uptake of-52.30 mg CO2/m2 , equivalent to 5.89 tonsC/ha/y was estimated. The calculated emissions during the fallow season were approximately 2.57 tons C/ha/y. We observed no significant relationship between CH4 emissions and CO2 fluxes.