Abstract: With closed static chamber and modified gas chromatograph (HP5890Ⅱ), the in situ measurements were made on the CO₂, CH₄ and N₂O emissions from winter-fallowed paddy fields in the hilly area of South China. Gas samples were taken simultaneously from the fields with and without rice stubble. The results showed that both of the fields had the peak value of CO₂ flux in the late afternoon. In the fields with and without rice stubble, the CH₄ flux was positive in the day time while negative in the night, and the N₂O flux in the day time was 1.79 and 1.58 times as much as that in the night, respectively. The diurnal average CO₂ flux in the field with rice stubble was significantly higher than that in bare field (P＜0.05). Correlation analysis demonstrated that the CO₂ flux in winter-fallowed paddy fields had significant correlations with soil temperature, aboveground temperature, and air temperature, suggesting that temperature was the main factor affecting the CO₂ emission from rice field after harvesting. During the observation time (from 2003-11-10 to 2004-01-18), the average CO₂, CH₄ and N₂O fluxes in the field with rice stubble were (180.69 ± 21.21)mg·m^-2·h^-1,(-0.04±0.01)mg·m^-2·h^-1 and (21.26±19.31)μg·m^-2·h^-1, respectively. Compared with bare field, the CO₂ flux in the field with rice stubble was 13.06% higher, CH₄ absorption increased by 50%, while N₂O flux was 60.75% lower. It was concluded that the winterfallowed paddy field in hilly area of South China was the source of atmospheric CO₂ and N₂O, and the sink of atmospheric CH₄.

Key words: Soil hydrolase, Kinetics, Properties