双季稻田种植不同冬季作物对甲烷和氧化亚氮排放的影响

研究双季稻收获后填闲种植不同冬季作物在其生长季节内CH₄和N₂O的排放特征,对合理利用冬闲稻田,发展冬季作物生产及合理评价不同种植模式具有重要意义。采用静态箱-气相色谱法对冬季免耕直播黑麦草、紫云英、油菜以及翻耕移栽油菜和冬闲的双季稻田中甲烷(CH₄)和氧化亚氮(N₂O)排放进行了分析。结果表明:在冬季作物生长期,CH₄、N₂O平均排放通量和总排放量均表现为翻耕移栽油菜＞免耕直播黑麦草＞免耕直播油菜＞免耕直播紫云英＞冬闲。不同冬季作物稻田CH₄和N₂O总排放量与对照(冬闲)的差异均达到极显著水平(P<0.01);翻耕移栽油菜的双季稻田中CH₄和N₂O排放量最高,分别达2.989 g/m²和0.719 g/m²。翻耕移栽油菜稻田的CH₄和N₂O温室效应总和也最大,为2893.92 kg CO₂/hm²;免耕直播黑麦草和免耕直播油菜处理次之,而免耕直播紫云英处理最低。种植不同冬季作物促进了稻田生态系统CH₄和N₂O的排放。

Effects of different winter covering crops cultivation on methane (CH4) and nitrous oxide (N2O) emission fluxes from double-cropping paddy field

Methane(CH4) and nitrous oxide(N2O) are two important trace gases,which are considered to have 15—30 and 150—200 times more radioactively active than CO2,respectively.It is well known that agricultural soils are the major sources of atmospheric CH4 and N2O.IPCC(2007) revealed that global warming potentials(GWPs) of CH4 and N2O are different.Previous researches have investigated some factors that affect the rates of CH4 and N2O emission fluxes,such as soil properties,climate,water regime,organic matter incorporation and plant physiology.However,the effects of different winter covering crops cultivation on CH4 and N2O emission fluxes from double-cropping paddy fields is unclear.So the quantitative and possible mechanisms dependence of CH4 and N2O emission fluxes from double-cropping paddy fields on different winter covering crops cultivation is still far from being understood.Hence,the static chamber-gas chromatography(GC) technique with manual method was chosen to identify the effects of different winter covering crops cultivation(including no-tillage ryegrass and double rice cropping(T1),no-tillage Chinese milk vetch and double rice cropping(T2),tillage rape and double rice cropping(T3),no-tillage rape and double rice cropping(T4) and fallow and double rice cropping(CK)) on CH4 and N2O emission fluxes from double-cropping paddy fields in subtropical regions of China(28°08′18″ N,113°12′0″ E).The results showed that the fluxes and emission of CH4 and N2O was varied with different winter covering crops cultivation patterns,and generally followed the series T3>T1>T4>T2>CK,and ANOVA revealed that the emission fluxes of CH4 and N2O were significantly(P<0.01) more from the four treatments during the whole growth stage than that of fallow and double rice cropping(CK).In addition,2.284,1.073,2.989,1.731 and 0.668 g/m2 CH4 emission fluxes were observed from the treatment of T1,T2,T3,T4 and CK during the whole growth stage of winter covering crops,respectively.CH4 emissions during the whole growth stage under T1,T2,T3 and T4 treatments were increased by 241.92%,60.63%,347.46% and 159.13%,respectively.Similarly,the treatments of T1,T2,T3,T4 and CK had also the N2O emission during the winter covering crops whole growth stage with 0.588,0.479,0.719,0.544 and 0.342 g/m2,respectively.N2O emissions during the whole growth stage under T1,T2,T3 and T4 treatments were increased by 71.93%,40.06%,110.23% and 59.06%,respectively.The treatments of T3,T1 had not only the largest CH4 emissions during the winter covering crops whole growth stage with 2.989 and 2.284 g/m2,but also the largest N2O emissions with 0.719 and 0.588 g/m2 from double-cropping paddy fields,respectively.Our study also indicated that GWPs of CH4 and N2O from double-cropping paddy fields was varied with different winter covering crops and followed the general series T3>T1>T4>T2>CK.The treatment of T3 also had the largest GWPs of CH4 and N2O from double-cropping paddy fields with 2893.92 kg CO2/hm2,while T1 and T4 had the secondly GWPs of CH4 and N2O from double-cropping paddy fields with 2326.49 and 2056.75 kg CO2/hm2,and the T2 had the lowest GWPs of CH4 and N2O from double-cropping paddy fields with 1698.05 kg CO2 /hm2,respectively.Our results clearly demonstrate that CH4 and N2O emission from double-cropping paddy fields were significantly promoted by planting different winter covering crops in double paddy field ecosystem.Further studies investigating the regulated factors of CH4 and N2O emissions from double-cropping paddy fields is therefore warranted.