[1] A 3-year field experiment was conducted to simultaneously measure methane (CH 4 ) and nitrous oxide (N 2 O) emissions from rice paddies under various agricultural managements including water regime, crop residue incorporation, and synthetic fertilizer application. In contrast with continuous flooding, midseason drainage incurred a drop in CH 4 fluxes while triggering substantial N 2 O emission. Moreover, N 2 O emissions after midseason drainage depended strongly on whether or not fields were waterlogged due to intermittent irrigation. Urea application tended to reduce CH 4 emissions but significantly increased N 2 O emissions. Under a water regime of flooding-midseason drainagereflooding-moist intermittent irrigation but without water logging (F-D-F-M), both wheat straw and rapeseed cake incorporation increased CH 4 emissions by 252%, and rapeseed cake increased N 2 O by 17% while wheat straw
The reactive nitrogen (Nr) pollution is a serious environmental problem. A wise application of nitrogen fertilizer is important for mitigating Nr loss. Field experiments were undertaken during the direct-seeded rice and winter-wheat growing seasons from 2014 to 2015 in Nanjing, one of the typical rice-wheat rotation regions in China, to evaluate the potential of different nitrogen fertilizers for mitigating Nr (NO, NH emissions, and NO leaching) losses. Seven different fertilizer treatments were included in this study: a no fertilizer treatment (NF), conventional fertilizer (CF), urea-ammonium mixed nitrogen fertilizer (UA), stabilized urea (UHD; urea + hydroquinone + dicyandiamide), sulfur-coated urea (SCU), urea formaldehyde (UF) and organic fertilizer (OF). In comparison with the CF, all the fertilizer treatments except for UA decreased NH volatilization by 14.5-36.0% (p < 0.05), while none of the N fertilizers had an obvious mitigation effect on NO emissions and NO leaching during the rice and wheat seasons. Further analyses showed that the UHD, UF and OF treatments reduced the yield-scaled Nr loss (NLI) by 32.6-42.5% for the rice season and by 15.5-34.5% for the wheat season as compared to the CF; other treatments relative to CF had no obvious effect with regard to lowering the NLI. UHD, UF and OF could be adopted as an effective mitigation alternative to reduce Nr loss and maintain crop yield in future rice/wheat production. Graphical abstract ᅟ.
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