Impact of intercropping of rice cultivars on methane emissions
Diversified farming of crop cultivars is an effective measure for improving agroecosystem functions.However,there is still a lack of research on the effects of mixed planting of different cultivars on greenhouse gas(GHG)emissions.In this study,rice was used as an example to explore the impact of intercropping of different cultivars on methane(CH4)emissions through an in situ pot experiment.The cultivars Changnongjing No.8 and Wandao No.153,which have high CH4 emissions,and the cultivars Suxiangjing No.100 and Ⅱ-you No.084,which have low CH4 emissions,were selected as experimental materials.A total of eight treatments were set up in this study.The monocultures of four cultivars were as follows:the monoculture of Changnongjing No.8(referred to as CN),the monoculture of Wandao No.153(WD),the monoculture of Suxiangjing No.100(SX)and the monoculture of Ⅱ‒you No.084(ⅡY).Additionally,intercropping systems were set up between two CH4 high-emission cultivars and two CH4 low-emission cultivars:intercropping of Changnongjing No.8 and Suxiangjing No.100(CN+SX),intercropping of Changnongjing No.8 and Ⅱ‒you No.084(CN+ⅡY),intercropping of Wandao No.153 and Suxiangjing No.100(WD+SX),and intercropping of Wandao No.153 andⅡ‒you No.084(WD+ⅡY).In the intercropping treatments,the two cultivars were planted at a ratio of 1∶1.The results showed that all the intercropping treatments either significantly increased or maintained rice yield,and that the CH4 emissions varied significantly among the different intercropping treatments.Compared with the expected values,the CN+SX treatment resulted in a significant reduction in CH4 emissions,while the CN+ⅡY and WD+ⅡY treatments significantly increased the CH4 emissions.Compared with the monoculture of CH4 high-emission cultivars,the intercropping of Suxiangjing No.100 with two CH4 high-emission cultivars significantly reduced the average abundance of the methanogenic archaeal mcrA gene during the growing season,but Ⅱ‒you No.084 had a significant effect only when intercropped with Wandao No.153.For the intercropping treatments except CN+SX,the average abundance of the methanotrophic bacterial pmoA gene during the growing season was significantly lower than that of the corresponding monoculture.This study suggested that the intercropping of rice cultivars can enhance rice yield and also reduce CH4 emissions,but the appropriate combinations of intercropped cultivars should be selected carefully.
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