title: Influence of intercropping and intercropping plus rhizobial inoculation on microbial activity and community composition in rhizosphere of alfalfa (Medicago sativa L.) and Siberian wild rye (Elymus sibiricus L.).
abstract: Alfalfa-Siberian wild rye intercropping is the predominant cropping system used to produce forage in China. In this study, the effects of intercropping and intercropping-rhizobial inoculation on soil enzyme activities, microbial biomass and bacterial community composition in the rhizosphere were examined. In both treatments, the yield of alfalfa, microbial biomass and activities of soil urease, invertase and alkaline phosphatase in the alfalfa rhizosphere were markedly increased, whereas there was a slight increase in the yield of Siberian wild rye, few impacts on soil microbial biomass, and decreased enzyme activities (except for urease) in the Siberian wild rye rhizosphere. Terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes indicated that Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Firmicutes, Actinobacteria and Bacteroidetes were the major bacterial groups in the rhizosphere of both plants. However, intercropping and rhizobial inoculation induced some shifts in the relative abundance of them. Nitrosomonas and Nitrosospira groups were detected in all treatments by the T-RFLP patterns of ammonia monooxygenase subunit A (amoA) gene, but the relative abundance of Nitrosomonas increased and that of Nitrosospira decreased in the intercropping-rhizobial inoculation treatment. Both treatments tended to increase the diversity of amoA. Conclusively, the two treatments clearly affected soil microbial composition and soil enzyme activities, which might be reflected in changes in yield.
authors.affiliation: State Key Laboratory for Agrobiotechnology, College of Biological Sciences and Center for Biomass Engineering, China Agricultural University, Beijing, China.
authors.forename: Yan Mei
authors.initials: YM
authors.lastname: Sun
authors.forename: Nan Nan
authors.initials: NN
authors.lastname: Zhang
authors.forename: En Tao
authors.initials: ET
authors.lastname: Wang
authors.forename: Hong Li
authors.initials: HL
authors.lastname: Yuan
authors.forename: Jin Shui
authors.initials: JS
authors.lastname: Yang
authors.forename: Wen Xin
authors.initials: WX
authors.lastname: Chen
mesh_terms: D000383:Agriculture / Q000379:methods*; D001419:Bacteria / Q000145:classification / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D044822:Biodiversity; D018533:Biomass; D004269:DNA, Bacterial / Q000235:genetics; D031749:Elymus / Q000382:microbiology*; D000455:Medicago sativa / Q000382:microbiology*; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012987:Soil / Q000032:analysis; D012988:Soil Microbiology
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012987:Soil