Effects of different rice varieties on greenhouse gas emissions from paddy fields in Chongqing

【Objective】 To explore the effects of different rice varieties on greenhouse gas emissions in paddy fields,which could screen out high-yielding rice varieties with low greenhouse gas emissions suitable for cultivation in Chongqing.【Method】 Through field experiments,the fluxes of methane （CH₄） and nitrous oxide （N₂O） from 6 major rice varieties （Zhongzheyou H7,Yuliangyouhuazhan,Q Xiangyou 352,Shennongyou 446,Yuxiangyou 8133 and Yuxiang 203） in Chongqing were continuously monitored using the static chamber-gas chromatography method.The rice yields were measured at harvest,and the global warming potential and greenhouse gas emission intensity of each variety were com‐pared. 【Result】 Among the 6 rice varieties,only Zhongzheyou H7 showed a bimodal trend in CH₄ flux,with peaks occur‐ring during the heading stage-filling stage and the maturity stage-harvest stage.The CH₄ fluxes of the other 5 varieties showed an unimodal trend,with peaks occurring during the heading stage-filling stage.The total CH₄ emissions of different varieties ranged from 175.77 to 274.10 kg/ha.Among them,Q Xiangyou 352 had the lowest total CH₄ emission,while Yuxiangyou 8133 had the highest,and there was significant difference between the two （P＜0.05,the same below）.The obvious emission peak of N₂O occurred after the paddy field was drained,with total emission ranging from-0.100 to0.464 kg/ha.There was no significant difference in the total N₂O emission among the varieties （P＞0.05）,and the total N₂O emission of Yuxiangyou 8133 was negative.The rice yields of different varieties ranged from 4.94 to 8.20 t/ha.Among them,Q Xiangyou 352 had the highest yield,while Yuliangyouhuazhan had the lowest yield,and there was sig‐nificant difference between the two.The global warming potential analysis showed that Zhongzheyou H7 had the highest global warming potential,reaching 7.67 t CO₂e/ha,while Q Xiangyou 352 had the lowest global warming potential,at4.98 t CO₂e/ha.The greenhouse gas emission intensity of different rice varieties ranged from 0.61 to 1.54 t CO₂e/t.Among them,Q Xiangyou 352 had the lowest greenhouse gas emission intensity,which was significantly lower than that of other varieties,while Zhongzheyou H7 had the highest greenhouse gas emission intensity.【Conclusion】 Considering both yield and greenhouse gas emission,Q Xiangyou 352 has the highest yield and the lowest CH₄ emission and greenhouse gas emission intensity,and it is suitable for promotion in Chongqing and regions with similar conditions.