Drainage and tillage practices in the winter fallow season mitigate CH4and N2O emissions from a double-rice field in China

摘要

Traditional land management (no tillage, no drainage, NTND) during the winterfallow season results in substantial CH and NO emissions fromdouble-rice fields in China. A field experiment was conducted to investigatethe effects of drainage and tillage during the winter fallow season onCH and NO emissions and to develop mitigation options. Theexperiment had four treatments: NTND, NTD (drainage but no tillage), TND(tillage but no drainage), and TD (both drainage and tillage). The study wasconducted from 2010 to 2014 in a Chinese double-rice field. During winter,total precipitation and mean daily temperature significantly affectedCH emission. Compared to NTND, drainage and tillage decreased annualCH emissions in early- and late-rice seasons by 54 and33 kg CH ha yr, respectively. Drainage and tillageincreased NO emissions in the winter fallow season but reduced it inearly- and late-rice seasons, resulting in no annual change in NOemission. Global warming potentials of CH and NO emissions weredecreased by 1.49 and 0.92 t CO eq. ha yr,respectively, and were reduced more by combining drainage with tillage,providing a mitigation potential of1.96 t CO eq. ha yr. A low total C content and highC / N ratio in rice residues showed that tillage in the winter fallowseason reduced CH and NO emissions in both early- and late-riceseasons. Drainage and tillage significantly decreased the abundance ofmethanogens in paddy soil, and this may explain the decrease of CHemissions. Greenhouse gas intensity was significantly decreased by drainageand tillage separately, and the reduction was greater by combining drainagewith tillage, resulting in a reduction of 0.17 t CO eq. t. Theresults indicate that drainage combined with tillage during the winter fallowseason is an effective strategy for mitigating greenhouse gas releases fromdouble-rice fields.