稻鱼共生养鱼密度对稻田甲烷排放的影响

Rice-fish symbiosis patterns with different densities affect methane emissions from double-cropping paddy fields

为探究不同密度稻鱼共生模式对双季稻田甲烷(CH_(4))排放及有机碳的影响,本研究于2022—2023年在湖南省长沙县路口镇进行大田试验,设置双季稻不养鱼常规种植(CK)、双季稻养鱼3000尾·hm^(−2)(DY1)、6000尾·hm^(−2)(DY2)3个处理,采用大区试验设计,分析不同密度稻鱼共生模式对双季稻田CH_(4)排放及土壤有机碳(SOC)、水溶性有机碳(WDOC)及微生物量碳(MBC)的影响。结果表明:与CK相比,两年的稻鱼共生模式增加了CH_(4)季节累积排放通量和周年累积排放量;不同密度稻鱼处理之间相比,DY1处理2022、2023年CH_(4)周年累积排放显著高于DY2处理17.67%、13.35%(P<0.05)。稻鱼处理在2022年早、晚稻成熟期较CK分别提高了土壤SOC含量8.18%~14.10%和47.26%~56.42%;在2023年分别提高了22.00%~22.77%和23.74%~24.91%。土壤WDOC含量达到峰值时,与CK相比,2022年稻鱼处理的早、晚稻时期分别提高了133.39%~179.35%(P<0.05)、27.72%~40.78%(P<0.05),2023年稻鱼处理的早、晚稻时期分别提高了6.98%~14.16%(P<0.05)、68.51%~74.83%(P<0.05)。稻鱼处理土壤MBC含量在2022年早稻时期显著提高了544.86%~719.41%(P<0.05),晚稻高峰时显著提高了15.89%~32.68%(P<0.05),2023年早稻时期MBC含量变化较小,晚稻高峰时DY2较CK显著提高了210.35%(P<0.05)。综上,稻鱼共生模式增加了土壤SOC、WDOC、MBC含量且促进了CH_(4)排放,但CH_(4)排放随养鱼密度增加而降低。本研究发现,稻鱼共生模式对双季稻田CH_(4)减排具有意义,且当养鱼密度在6000尾·hm^(−2)时效果最佳。

The objective of this study is to explore the effects of rice-fish symbiosis patterns at different densities on methane(CH_(4))emissions and organic carbon in double cropping paddy fields.In this study,a field experiment was conducted in Lukou Town,Changsha County,Hunan Province from 2022 to 2023,and three treatments were set up:conventional planting of double cropping rice without fish culture(CK),double cropping rice fish farming of 3000 fish·hm^(−2)(DY1)and 6000 fish·hm^(−2)(DY2),and the regional experimental design was adopted.The effects of rice-fish symbiosis patterns at different densities on CH_(4)emissions and soil organic carbon(SOC),water soluble organic carbon(WDOC)and microbial biomass carbon(MBC)in double-cropping paddy fields were analyzed.The results showed that compared with CK,the two-year rice-fish symbiosis model increased the seasonal cumulative emission flux and annual cumulative emission of CH_(4).Compared with the different densities of rice-fish treatments(DY1 and DY2),the cumulative annual emissions of CH_(4)in 2022 and 2023 of DY1 treatment were significantly higher than those of DY2 treatment by 17.67%and 13.35%(P<0.05).In 2022,the early and late rice maturation stages increased the soil SOC content by 8.18%-14.10%and 47.26%-56.42%,respectively.In 2023,it increased by 22.00%-22.77%and 23.74%-24.91%,respectively.When the soil WDOC content reached the peak,compared with CK,the early and late rice stages of rice-fish treatment in 2022 increased by 133.39%-179.35%(P<0.05)and 27.72%-40.78%(P<0.05),respectively,and the early and late rice stages of rice-fish treatment in 2023 increased by 6.98%-14.16%(P<0.05)and 68.51%-74.83%(P<0.05),respectively.In 2022,the MBC content of rice-fish treatment soil increased significantly by 544.86%-719.41%(P<0.05)in early rice and 15.89%-32.68%(P<0.05)at the peak of late rice,and the MBC content in early rice in 2023 changed slightly,and DY2 increased significantly by 210.35%compared with CK in late rice(P<0.05)。In conclusion,the rice-fish symbiosis pattern increase the contents of soil SOC,WDOC and MBC and promoted CH_(4)emissions,which decrease with the increase of fish density.This study found that the effect of rice-fish symbiosis on CH_(4)emission reduction in double-cropping paddy field has important promotion significance in production practice,and the effect is best when the density is 6000·hm^(−2).