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.  

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

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 

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. 

• 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

• 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

• 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

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.