Soil biology includes a variety of soil microbes, bacteria and larger fauna such as earthworms and collembolans.

Soil fungi

A teaspoon of soil can contain around one million fungi. Some of these are parasitic and detrimental to plants, but some are mutualistic and form beneficial associations with plants.

  • Mycorrhizal fungi create mutualistic symbioses with living plants. As the fungi has no chlorophyll, in this symbiotic relationship, they gain carbohydrates from the host plant through photosynthesis, in return for providing the host plant nutrients which it can't access in the soil itself.
  • Fungal diseases can also be caused by soilborne fungi, such as Gaeumannomyces graminis var. tritici which causes Take-all in wheat and devastates yields.

Soil bacteria

Soil bacteria can also be both mutualistic and parasitic to host plants.

  • Nitrogen fixing is carried out by free-living nitrogen-fixing bacteria in the soil (e.g. Azotobacter) or by those in the root nodules in leguminous plants (e.g. rhizobia). These bacteria have the ability to convert atmospheric nitrogen into nitrogen-containing substances which the host plant can access
  • Actinobacteria are crucial for the decomposition of organic material and contributing to soil hummus formation
  • Bacterial diseases are caused by pathogenic bacterial species. Common diseases include crown gall, caused by Agrobacterium tumefaciens.

Soil fauna

Soil fauna affect soil structure, organic matter cycling and hydrological functioning on different scales, from microbiota, to mesofauna to macrofauna. These include:

  • Earthworms (see earthworm page for more information)
  • Ants
  • Collembolans
  • Nematodes
  • Mites
  • Protozoa 


Related Organisations

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Connected Content

Earthworms are known as ecosystem engineers due to their ability to structurally, chemically and biologically transform the soil environment in which they live.

The intricate web of relationships between physical, chemical and biological soil components underpins crop and livestock health and productivity. Protecting soil health is also critical to environmental sustainability, as soils: • Exchange gases, such as carbon dioxide and nitrogen oxides, with the atmosphere • Regulate the flow of water and rainfall in the water cycle • Provide nutrients for plant growth, by breaking down organic matter and altering chemical fertilisers • Transform and store organic materials, as part of the terrestrial carbon cycle • Degrade contaminants applied through human activities or left by floods and aerial deposition A healthy soil is able to sustain, in the long term, these important functions. In a healthy soil, the interactions between chemistry (pH, nutrients and contaminants), physics (soil structure and water balance) and biology (including earthworms, microbes and plant roots) are optimised for the conditions in that place.   View more from AHDB GREAT Soils. Share resources you find helpful below.

The soil health scorecard brings together information about the chemical, physical and biological properties of soil. Watch Anne Bhogal give an overview of the research that has gone in to the Soil Health Scorecard.

Funded by AHDB and BBRO, this five-year Soil Biology and Soil Health Partnership is a cross-sector programme of research and knowledge exchange. The programme is designed to help farmers and growers maintain and improve the productivity of UK agricultural and horticultural systems, through better understanding of soil biology and soil health. See https://ahdb.org.uk/soil-biology-and-soil-health-partnership

Soil organic matter (OM) is all living or once-living materials in the soil.  OM provides a direct source of energy/food for many soil organisms: it is the fuel in the soil food web.  Turnover of OM successively releases and immobilises elements vital to the nutrition of crops. 

AHDB's GREAT Soils brings together all the work on Soils, to help farmers protect their soils and improve its productivity

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