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      Microbial community dynamics in long-term no-till and conventionally tilled soils of the Canadian prairies

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      HelgasonPhDThesis.pdf (3.184Mb)
      Date
      2010-01
      Author
      Helgason, Roberta Lynn
      Type
      Thesis
      Degree Level
      Doctoral
      Metadata
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      Abstract
      Adoption of no-till (NT) and reduced tillage management is widespread on the Canadian prairies and together form the basic platform of soil management upon which most crop production is based. Elimination of tillage in cropping systems changes the physical and chemical characteristics of the soil profile and can affect crop growth and ultimately yield. As such, understanding how soil biota, as drivers of nutrient turnover, adapt to NT is important for maximizing crop productivity and mitigating environmental damage in agroecosystems. This work aims to achieve a greater understanding of microbial community structure and function in long-term NT versus conventionally tilled (CT) soils. Community phospholipid and DNA fingerprinting did not reveal any consistent tillage-induced shifts in microbial community structure, but demonstrated a clear influence of depth within the soil profile. While tillage did not result in broad changes in the community structure, total, bacterial and fungal biomass was consistently greater near the surface of NT soils. Further examination at one site near Swift Current, SK revealed differences in microbial biomass and community structure in NT and CT in field-formed aggregate size fractions. Measurement of mineralization and nitrification at the same site indicated that differences in the early-season turnover of N may be related to physical rather than microbial differences in NT and CT soils. Potential nitrification was higher prior to seeding than mid-season, was not affected by tillage and was correlated with ammonia oxidizer population size of archaea, but not bacteria. This work indicates that edaphic soil properties and spatial distribution of resources in the soil profile, rather than tillage management, are the primary factors driving microbial community structure in these soils.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Soil Science
      Program
      Soil Science
      Supervisor
      Walley, Fran; Germida, Jim
      Copyright Date
      January 2010
      URI
      http://hdl.handle.net/10388/etd-01152010-153135
      Subject
      DNA fingerprint
      long-term experiment
      microbial functional groups
      microbial community
      tillage
      phospholipid fatty acid analysis
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