稻作模式改变对稻田CH_(4)和N_(2)O排放的影响

Effects of Changing Rice Cropping Patterns on CH_(4) and N_(2)O Emissions from Paddy Fields

长江中游稻作模式由传统中稻-冬季作物模式向再生稻发展的趋势明显,但关于稻作模式对稻田CH_(4)和N_(2)O排放的研究尚缺乏报道。以江汉平原3种模式为对象:稻-麦(RW)、稻-油(RR)和再生稻(Rr),采用静态箱-气相色谱法,研究稻田CH_(4)和N_(2)O排放的变化规律,同时监测土壤硝态氮(NO^(3-)-N)、铵态氮(NH_(4)^(+)-N)、pH和土温的动态变化,以期揭示不同稻作模式对温室气体排放的影响及影响因素。结果表明,在非水稻季,RW、RR和Rr处理的CH_(4)的累计排放量分别为6.34、9.35和8.63 kg·hm^(-2),N_(2)O平均排放通量分别为8.08、17.78和24.92μg·m^(-2)·h^(-1),表现为Rr>RR>RW;在水稻季,相比较RR处理,RW和Rr处理CH_(4)的累计排放量分别增加了158.27%和148.38%,且差异显著,其N_(2)O的累计排放量分别增加了34.89%和87.36%。Rr处理头季CH_(4)的排放量占整个水稻季87.64%,其N_(2)O平均排放通量头季要比再生季高35.99%。RW和Rr处理产量差异不显著,但要显著高于RR处理,其增幅分别为14.49%和24.40%。RR的全球增温潜势(GWP)和温室气体排放强度(GHGI)最低,其GWP比RW、Rr分别低45.05%和72.85%;GHGI分别降低了35.14%和63.64%。中稻季CH_(4)的排放速率与NH_(4)^(+)-N含量呈显著正相关(P<0.05),Rr处理下CH_(4)的排放量与NO^(3-)-N含量呈显著负相关关系(P<0.05),与土壤pH呈负相关,且差异极显著(P<0.01);中稻季N_(2)O的排放与NO^(3-)-N和土温负相关,差异不显著(P>0.05),Rr处理N_(2)O排放与NH_(4)^(+)-N呈显著正相关(P<0.05)。因此,在江汉平原稻-油模式不仅利用了冬闲田,提高作物种植产量,还有利于降低温室气体的排放,缓解全球增温潜势。

The rice cropping pattern in the middle reaches of the Yangtze River showed an obvious trend from the traditional medium rice-winter crop pattern to the regrowing-rice pattern.However,there were few reports on the effects of rice cropping pattern on CH_(4) and N_(2)O emissions from paddy fields.Three models of Jianghan Plain were taken as objects:Rice-wheat(RW),rice-rape(RR)and regrowing rice(Rr),to study the changes of rice cropping patterns effects on CH_(4) and N_(2)O emissions in paddy fields using static boxgas chromatography.Meanwhile,the dynamic changes of soil NO^(3-)-N,NH_(4)^(+)-N,pH and soil temperature were monitored,in order to reveal the effects and influencing factors of different rice cropping patterns on greenhouse gas emissions.The results showed that in the non-rice season,the cumulative CH_(4)emissions of RW,RR and Rr were 6.34 kg·hm^(-2),9.35 kg·hm^(-2)and 8.63 kg·hm^(-2),respectively.The average N_(2)O emission fluxes were 8.08μg·m^(-2)·h^(-1),17.78μg·m^(-2)·h^(-1) and 24.92μg·m^(-2)·h^(-1),respectively,in the order of Rr>RR>RW.In the rice season,compared with RR,the cumulative CH_(4)emissions of RW and Rr increased by 158.27%and 148.38%,respectively,and the cumulative N_(2)O emissions of RW and Rr increased by 34.89%and 87.36%,respectively.The CH_(4)emission of Rr in the first season accounted for 87.64%of the whole rice season,and the average N_(2)O emission flux in the first season was 35.99%higher than that in the regeneration season.The yields between RW and Rr shown no obvious difference,but were significantly higher than that of RR,which increased by 14.49%and 24.40%.RR had the lowest global warming potential(GWP)and greenhouse gas emission intensity(GHGI).GWP of RR was 45.05%and 72.85%lower than those of RW and Rr,respectively,while GHGI decreased by 35.14%and 63.64%,respectively.There was a significant positive correlation between CH_(4)emission and NH_(4)^(+)-N content in middle rice season(P<0.05),and a significant negative correlation between CH_(4)emission and NO^(3-)-N content in Rr(P<0.05),a significant negative correlation between CH_(4)emission rate and soil pH(P<0.01).The N_(2)O emission was negatively correlated with NO^(3-)-N and soil temperature in middle rice season,and the difference was not significant(P>0.05),while the N_(2)O emission was significantly and positively correlated with NH_(4)^(+)-N in Rr(P<0.05).Therefore,the RR model in Jianghan Plain not only makes use of idle winter farmland to increase crop yield,but also helps reduce greenhouse gas emissions and mitigate the global warming potential.