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

Content below is from across the PEP community and is not necessarily endorsed by Stewards or by PEP

Topic Comments


Interesting global initiative on Soil Biodiversity - www.globalsoilbiodiversity.org


Useful scientific paper on the Microbiome in journal Frontiers in Microbiology:

Microbe to Microbiome: A Paradigm Shift in the Application of Microorganisms for Sustainable Agriculture


Connected Content

Tell us how you are improving your soils. Share useful resources, organisations and initiatives.

Soil health has been broken down into measurable parts to help farmers optimise crop and grassland productivity. As part of the Soil Biology and Soil Health Partnership, a project in the AHDB & BBRO GREAT Soils programme, guidance and protocols have been issued to help practitioners benchmark their soils

The intricate web of relationships between physical, chemical and biological soil components underpins crop and livestock health and productivity.

Helping you protect your soil and improve its productivity.  AHDB's GREATSoils inititiative brings together practical information on soil management as well as links to soils research and knowledge exchange. Whether you need an introduction to soil biology or a detailed guide to improving field drainage, AHDB has information and guidance to support you. 

Our new book on Understanding and fostering soil carbon sequestration edited by Cornelia Rumpel, Director of Research in the Institute of Ecology and Environmental Sciences at the French National Research Center, provides an authoritative review of all the latest research in this important area.

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

The 3rd Global Soil Biodiversity Conference to be held in Dublin (Ireland) in 2023 will expand on previous GSBI conferences and convene the world’s leading experts in this interdisciplinary field of soil biodiversity science to present and discuss recent advances addressing the urgency of meeting global challenges which link to human, animal and plant health and a more sustainable world.  

Scientific paper in New Phytologist by scientists at China Agriculture University and James H

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. 

6 October 2023: AFBI Soils Conference - La Mon Hotel and Country Club, Belfast

We are pleased to announce that the next British Society of Soil Science Annual Conference will be a joint event with the Soil Science Society of Ireland and take place in Belfast on Monday 4 and Tuesday 5 December 2023.

Counting earthworms is a simple method for assessing soil biological health

Executive summary for policymakers and researchers

Improving soils by building soil organic matter is a win, win situation for everyone.

Biofumigation involves incorporating brassicaceous cover crops into the soil.

The British Society of Soil Science (BSSS) is delighted to announce the next Zoom into Soil webinar will take place on Wednesday 7 February from 12:00 - 1:00pm (UK time) and is free of charge to register.

Six Simple Steps for your soil to help improve the performance, health and long-term sustainability of your land

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