Methane emission from paddy fields and its affecting factors in hills of the central Sichuan Basin.

Methane emission fluxes from paddy fields growing rice all the year-round and paddy fields growing rice-wheat or rapeseed in rotation were measured with the static chamber-gas chromatographic technique in hills of the central Sichuan Basin.Results show that high CH_4 emission from the paddy fields under rotation and mono-rice cropping appeared in the middle of the rice growing season,and each had a typical peak.Effects of temperature,rice biomass,cropping system and planting model on CH_4 emission from paddy field have been analyzed and discussed.Significant positive relationship was found between 5 cm depths of soil temperature and CH_4 emission.Rice plants played an important role in CH_4 emission from the paddy field.The mean CH_4 emission fluxes from the paddy fields under rotation was 54.1%-65.1% lower than those under mono-rice cropping during the rice growing season.The intensified rice planting model could not only raise rice yield,but also reduce CH_4 emission from the paddy field.