Methane (CH₄) is one of the strongest greenhouse gases of which radiative force (0.48W m^-2) is 25 times greater than that of CO₂ on a molar basis. One of key sources for CH4 is agricultural lands such as rice paddy and radish fields. However, methane fluxes and related microbes in agricultural lands in Korea have not been extensively studied. In this study, methane dynamics along with related microbes (e.g., methanogens and methane oxidizers) were measured in radish fields and rice paddy at 4 different seasons; Spring, Summer, Autumn, and Winter. The average value of methane fluxes in rice paddy was higher than that in radish fields. Not only the methane emission rates, but the emission patterns were also different under different land use types. The most important factor for methane emission- in our site appeared to be oxygen availabilities, controlled by soil water content or soil porosity. When soil was saturated with water, methane emission was affected by temperature. Abundances of both methanogen and methane oxidizer were greater in rice paddy than those in radish fields. It is speculated that continuous changes in red-ox potential in rice paddy by irrigation allowed both methanogens and methanotrophic bacteria proliferate simultaneously.