Effects of organic amendments on aggregation and microbial community dynamics in soils

Project Overview

Project Type: Graduate Student
Funds awarded in 2008: $10,000.00
Projected End Date: 12/31/2011
Grant Recipient: University of Kentucky
Region: Southern
State: Kentucky
Graduate Student:
Major Professor:
Elisa D'Angelo
University of Kentucky
Major Professor:
Mark Williams
University of Kentucky

Annual Reports


  • Agronomic: vetches


  • Crop Production: cover crops, organic fertilizers
  • Natural Resources/Environment: biodiversity, soil stabilization
  • Soil Management: green manures, organic matter, soil analysis, soil microbiology, soil quality/health

    Proposal abstract:

    This project will evaluate the effects of soil amendments on aggregate formation, microbial residue accumulation, and microbial community dynamics in soils with different textures. Experimental soils will have their aggregate structure destroyed by being forced through a 250µm sieve. They will then be amended with either vetch, farmyard manure, OMRI certified compost, or no-amendment and incubated over 110 days. Soils will be destructively sampled on days 10, 25, 50, 80, and 110 and analyzed for macroaggregate formation and accumulation of the amino sugars glucosamine and muramic acid. These amino sugars are microbial residues that will be used to characterize the relative contributions of fungi and bacteria to aggregation processes. Changes in microbial community structure will also be assessed through analysis of microbial fatty acids on days 0, 25, 80 and 110. Relationships between amendment type, soil type, microbial parameters, and aggregate formation through time will be investigated. The hypothesis being tested is that, relative to other amendments, amendments that stimulate greater fungal activity will also promote greater macroaggregate formation. Anticipated outcomes of this work will provide information on soil management practices that stimulate soil structural enhancement by promoting a favorable microbial community. This information would be useful to those interested in maximizing the agronomic benefits associated with building and sustaining good soil structure.

    Project objectives from proposal:

    1. Observe accumulation of microbial residues (glucosamine derived from fungi and muramic acid derived from bacteria) and measures of microbial community structure (ester-linked fatty acid methyl esters) in small macroaggregates formed in soils receiving different organic inputs.

    2. Determine the influence of organic inputs on aggregate formation and aggregate stability in soils with different textures.

    3. Examine relationships between microbial residues, microbial community structure, and aggregate dynamics relative to organic inputs.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.