1.5 Soil biota are extremely varied and numerous

In about 5 cubic centimetres of agricultural soil you're likely to find:

  • At least 5 billion bacteria.
  • 5 million protozoa.
  • 5,000 nematodes (about 0.3-1.5 mm long) - the most common multi-cellular animals in soil.
  • About 6 mites and other microarthropods: this equates to up to 600,000 per square metre.

For larger organisms we have to look at quadrats of about a square metre:

  • Earthworms - maybe 300 per square metre (earthworm casts add more bacteria back to the soil than the worm eats. More bacteria mean healthier soil).
  • There may be around 20,000 kilometres of hyphae per square metre. Above ground, a meadow may look like separate plants. Underground, the plants are interconnected by their fungal associates (mycorrhizas) so they all belong to a single web of living things.
  • Small mammals; mice, voles, shrews, moles, which depend on the earthworms, arthropods and fungi for their nutrition, and in their turn feed predators; owls, foxes, etc., so the food web extends from microbes to large animals.

Resources Box

Life in the soil

Thomas E. Loynachan, Professor of Agronomy and Microbiology at Iowa State University, has created a set of 16 short digital videos showing the scope of life in the soil.

CLICK HERE to visit a page providing access to these.

Updated December 16, 2016