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- There is an incredible diversity of soil organisms including:
These organisms differ in size, abundance, biomass, tolerances and functions.
- 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.
- 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.
Knowledge Nuggets adapted from: Introduction to Soil Biology Top ten important points of the day
- A healthy soil has a diverse and metabolically active biological community that contributes to the functioning of balanced soil and water ecosystems.
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 Biological Communities- The Dirt on Dirt
Soil Biology and Soil Management - Soil Management Series
Soil Biological Fertility
Soil Biology and Antagonists of Nematodes
The Soil Biology Primer
Soil Ecology and Management
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