Soil macrofauna – earthworms

Earthworms engineer the soil environment, help with carbon cycling, improve water infiltration and plant productivity, and are an important food source for native birds.  

Back to: The function of soil biology

How to encourage earthworm activity

  • Add organic amendments to soil 
  • Leave crop residues, where possible 
  • Reduce tillage, where possible 

What do earthworms tell us?

Earthworms are an indicator of soil health, being impacted by pH, waterlogging, compaction, tillage, rotation, and organic matter management:  

  • A good presence of earthworms across the field means their benefits are likely to be widespread  
  • High numbers of earthworms indicate the potential for significant benefits to plant productivity  
  • The presence of each ecological group indicates the potential for specific earthworm benefits such as carbon cycling, nutrient mobilisation, and/or water infiltration 

Ecological groups of earthworms

There are up to 10 common earthworm species in agricultural soils, and these can be grouped into three ecological types: epigeic, endogeic and anecic earthworms  each group having a unique and important function. 

Epigeic (litter-dwelling earthworms)

Small dark red-headed epigeic earthworm
  • Dark red-headed worms
  • Small (< 8 cm) in size, typically about the length of a matchstick
  • Often fast-moving
  • Sensitive to tillage (detrimental effect)
  • Benefit from organic matter management such as manure applications
  • Play a role in carbon cycling
  • Prey for native birds

Endogeic (topsoil earthworms)

Medium sized pale-coloured endogeic earthworm
  • Pale coloured and green worms (not red)
  • Small to medium size
  • Often curl up when handled, and green worms may emit a yellow fluid
  • The most common earthworm group found in arable fields
  • Benefit from organic matter management such as manure applications
  • Play a role in soil aggregation and nutrient mobilisation for plants

Anecic (deep burrowing earthworms)

Large dark-headed anecic earthworm
  • Dark red or black-headed worms
  • Large (>8 cm), typically similar size to a pencil
  • Make deep vertical tunnels up to 2 m
  • Often found below surface earthworm casts or midden residue piles
  • Feed at night, foraging the soil surface around their burrow for litter
  • Commonly found in grassland but often absent from ploughed fields and where there is no surface litter
  • Sensitive to tillage (detrimental effect)
  • Benefit from organic matter management such as manure applications and straw return
  • Deep burrows improve aeration, water infiltration and root development

Identifying adult and juvenile earthworms

Adult earthworms have a clearly developed saddle (reproductive ring), and juveniles do not. You may need to rinse worms with water to determine if a saddle is present. Size is not a good indicator of maturity as adult earthworms typically range in size from 2 cm to 15 cm, depending on species.

Adult earthworm with saddle (reproductive ring)

Useful links

See how soil organisms stabilise soil structure

Discover the soil food web

Learn about different ecological groups of nematodes

Find out more about soil microbiology in agriculture

GREATsoils

Image of staff member Amanda Bennett

Amanda Bennett

Environment Scientist
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