By the method of static opaque chamber/ modified gas chromatography,a one year field experiment was conducted to measure
in situ the CH 4 and N 2O
emission from a winter time flooded paddy field in a hilly area of Southwest China.Gas samples were taken simultaneously from rice involved and rice uninvolved plots.The results showed that during rice
growth period,the CH 4 emission from the winter time flooded paddy field was higher than that from other paddy fields,but largely lower than many previous reports for the similar regions in Southwest China.The average flux of CH 4 emission from rice involved plots was 22.76±2.76 mg CH 4·m -2 ·h -1 during rice growth period,9.64±1.17 mg CH 4·m -2 ·h -1 per year,and 1.43±0.20 mg CH 4·m -2 ·h -1 during non rice growth season; while that from rice uninvolved plots was only 2.03±0.18 mg CH 4·m -2 ·h -1 per year,markedly lower than those from rice involved plots.During rice growth season,the mean emission rate of CH 4 and N 2O was 4.53±0.38 mg CH 4·m -2 ·h -1 and 32.01±5.02 μg N 2O·m -2 ·h -1 from rice uninvolved plots,but reached to 22.76±2.76 mg CH 4·m -2 ·h -1 and 73.04±5.03 μg N 2O·m -2 ·h -1 from rice involved plots,respectively.Rice involvement resulted in 302% increment of CH 4 and 128% increment of N 2O emission.There was a clear trade off between CH 4 and N 2O emission in paddy fields.Even with a span of 500 years,our calculation showed that in this winter time flooded paddy field,the GWP contributed by N 2O production was 7 9% of the CH 4 contribution,and thus,the greenhouse effect of N 2O production from this field was very small.