Diel Variation of Methane Emission from a Subtropical Paddy Field of South China in the Second Crop Season

Rice paddy has been identified as one of the important sources of the atmospheric methane and has large variability in emission estimates. This study was conducted to evaluate CH₄ emission from a subtropical paddy field of south China with closed static chamber and a modified gas chromatograph (HP5890 ) in situ in the second crop season. Gas samples were taken simultaneously from rice-involved and rice-free plots. Results showed that the diel change of CH₄ flux had one or two peak values in a day in the crop growing season. The diel mean CH₄ flux from rice-involved plot was in the order: tillering stage (3.61±0.23) >; flowering stage (0.09±0.06) >; booting stage (0.12±0.12) (mg·m·2h-1).The diel mean CH₄ flux of rice-involved plot was significantly higher than that of rice-free plot in the tillering stage (p<;0.01). It showed no significant correlation between CH₄ flux and temperature. The CH₄ flux was affected by soil moisture. As a whole, rice plants played a key role on the CH₄ emission from paddy field.