Greenhouse Gas Emissions from Northeast China Rice Fields in Fallow Season

Abstract CH 4 , N 2 O and CO 2 emissions from northeast Chinese rice fields were measured in the fallow season (November to March) to investigate the effects of freezing-thawing on the emissions. Both CH 4 emission from and atmospheric CH 4 oxidation by the soil occurred, but the flux was small. During the fallow season, rice fields acted as a minor source of atmospheric CH 4 , which accounted for about 1% of the CH 4 emission during the rice growing period. The field was also a substantial source of atmospheric N 2 O, which ranged between 40 to 77 mg m −2 and accounted for 40%–50% of the annual N 2 O emission. The largest N 2 O flux was observed in the thawing period during the fallow season. Laboratory incubation tests showed that the largest N 2 O flux came from the release of N 2 O trapped in frozen soil. Tillage and rice straw application (either mulched on the soil surface or incorporated in the soil) stimulated the CH 4 and CO 2 emissions during the fallow season, but only straw application stimulated N 2 O emission substantially.