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Rice is a major crop that feeds more than half of global population. Rice paddy playscomplex roles in carbon cycle by emitting CH4 to the atmosphere while CO2 is sequesteredfrom or released to the atmosphere. Here, we present 3.5 years of eddy covariancemeasurements of CH4 and CO2 fluxes over an intermittently-irrigated rice paddy in Korea intandem with carbon stock measurements in leaf, stem, grain, and root. The interannualvariation of CO2 fluxes was little although the timings of transplantation and harvest weredifferent for each year. Rice paddy acted as a slight sink or neutral in CO2 (-47.3 ± 50.9 g Cm−2 y−1; mean ± 95% confidence interval) with 942.2 ± 129.4 g C m−2 y−1 and894.9 ± 106.5 g C m−2 y−1 for gross primary production (GPP) and ecosystemrespiration (Reco), respectively. Carbon stock in rice showed large interannualvariation (760.2 ± 183.7 g C m−2) with 70 ± 19.8 g C m−2, 232.1 ± 83.3 g Cm−2, 378.2 ± 75.5 g C m−2, and 79.8 ± 12.8 g C m−2 for leaf, stem, grain, androot, respectively. The rice paddy emitted 21.7 ± 2.5 g C m−2 y−1 of CH4. Whenconsidering the global warming potential of CH4 (197.3 g CO2-Ceq m−2 y−1),the paddy shift from carbon sink to source (150 g CO2-Ceq m−2 y−1). The CH4flux showed a bimodal seasonal pattern caused by the mid-season drainage whichturned the soils aerobic conditions so prohibited CH4 emissions. The irrigationpractices, which are different every year, resulted in the significant interannualvariation of CH4 emission (± 7%). These findings will be useful to understand carbonbudgets and cycles, and develop carbon and water managements in rice paddy. [ABSTRACT FROM AUTHOR]