Soil Biology

 Knowledge Nuggets | Fact Sheets | Research Papers

Knowledge Nuggets

  • There is an incredible diversity of soil organisms including:
    • roots, microorganisms such as bacteria and fungi,
    • micro fauna such as nematodes and protozoa,
    • mesofauna such as mites, springtails,
    • macrofauna such as termites, ants, and earthworms.
    These organisms differ in size, abundance, biomass, tolerances and functions.
  • Each type of organism has important jobs that contribute to the health of the soil ecosystem. While most organisms derive energy and nutrients from organic matter, bacteria derive energy from many metabolic reactions such as from the sun or chemicals.
  • Most organisms need oxygen for respiration. Bacteria can utilize other oxidized compounds as external electron acceptors (anaerobic respiration) or utilize internal electron acceptors (fermentation) and thus be active under a range of anaerobic conditions.
  • The interactions of these organisms in a complex food web are responsible for the conversion of energy, the decomposition of organic matter, and recycling of nutrients in soil.
  • Decomposition of organic matter and the mineralization or immobilization of nutrients is dependent on the carbon and nutrient availability either in substrate or in the environment, the nutrient demands of the degraders and the structure of the compounds being degraded.
  • Relationships are important in ecosystem functions. Fungi and plants work together to increase water uptake and nutrient sequestration for the plants. Bacteria and plants (e.g. Rhizobium and legumes) work together to fix nitrogen. Microbes and earthworms work together to break down plant litter.
  • Soil organisms not only break down soil organic matter but also degrade and detoxify many unnatural compounds.
  • The biology of an ecosystem must be understood within the context of chemistry and physics. Organisms both affect and are affected by the chemistry and the physical structure of the soil.
  • Most biological activity is in the soil surface and is dependent on moisture, air, supply of food, physical protection, pH, etc. and is influenced by land management practices.
  • A healthy soil has a diverse and metabolically active biological community that contributes to the functioning of balanced soil and water ecosystems.
Knowledge Nuggets adapted from: Introduction to Soil Biology Top ten important points of the day


A Brief Overview of Nutrient Cycling in Pastures

Assessing the Pasture Soil Resource

Calling on More Troops – New Beetles Help Degrade Dung on Canadian Pastures - available in PDF format only

Common dung beetles on pasture - available in PDF format only

Nutrient Cycling in Pastures

Soil Biology

Soil Biological Communities- The Dirt on Dirt

Soil Biology and Soil Management - Soil Management Series

Soil Biology

Soil Biological Fertility

Soil Biology and Antagonists of Nematodes

The Soil Biology Primer

Soil Ecology and Management

Research Papers
Complexity and composition of pasture swards affect plant productivity and soil organisms - available in PDF format

Evaluation of the "bait-lamina test" to assess soil microfauna feeding activity in mixed grassland - available in PDF format

Impact of Pesticides on Soil Microbial Diversity, Enzymes, and Biochemical Reactions

Long term assessment of management of an annual legume green manure crop for fallow replacement in the Brown soil zone - available in PDF format

Root biomass and shoot to root ratios of perennial forage crops in eastern Canada - available in PDF format

  For more information about the content of this document, contact Grant Lastiwka.
This information published to the web on June 7, 2004.
Last Reviewed/Revised on March 2, 2017.

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