Earthworm
Lumbricidae
Role in the garden
The invisible worker of the soil: it aerates, drains, mixes the organic matter and produces casts very rich in nutrients. The meta-analysis by van Groenigen et al. (Scientific Reports, 2014) reports an average +25% yield in trials comparing soils with and without worms (pot and field trials, with residue inputs).
Activity period
All year (active as soon as the soil is moist and cool)
How to attract / manage it
By digging its burrows, it lets air, water and roots through. It turns dead leaves, compost and residues into casts rich in nitrogen, phosphorus, potassium, calcium and magnesium, with a pH close to neutral.
Practical guide
Where to find them
Covered, living soils: a mulched vegetable garden, meadows, woodland floor, compost heaps, no-dig beds. The richer the soil in organic matter, the larger the population.
Prevention
Do not turn the soil deeply (no intensive digging, which cuts the worms and destroys their burrows). Cover the soil permanently (mulch, green manures, leaves). Regularly add organic matter (compost, RCW, crop residues). Avoid aggressive pesticides and fertilisers.
Action / control
To be favoured absolutely: a soil rich in earthworms is more supple, more stable, retains water better and feeds plants better. Their burrows significantly improve water infiltration, which limits runoff and capping.
Sources
- van Groenigen, J.W. et al. (2014). Earthworms increase plant production: a meta-analysis. Scientific Reports, 4, 6365.
- Blouin, M. et al. (2013). A review of earthworm impact on soil function and ecosystem services. European Journal of Soil Science, 64(2), 161-182.