The earthworm is the organic garden’s best ally — and the most reliable indicator of soil health. 🪱 Plenty of earthworms means good soil; few or none means trouble. Based on the ÖMKi Research Institute’s 2024 publication, here’s what every gardener can do for their soil life.
🪱 Why are earthworms so important?
Earthworms can make up 80% of living soil biomass. Their work is irreplaceable:
| What earthworms do | Effect in your garden |
|---|---|
| 🌍 Burrow through the soil | 50% less runoff, reduces erosion |
| 🌿 Pull organic matter down into soil | Accelerates composting, forms humus |
| 💧 Improve soil structure | Crumbly soil, better water retention, easier root growth |
| 🧪 Release ammonia | Increases nitrogen availability for plants |
| 🛡️ Suppress pathogens | Vermicompost reduces pesticide need by 75%+ |
💡 ÖMKi data (2024): Earthworm presence increases crop yield by 25% and above-ground biomass by 23% — without chemicals.
📊 How much does tillage matter?
No-till areas support 2–9 times more earthworms than ploughed land. After 5 years of ploughing a former meadow, populations collapsed:
| Situation | Earthworms/m² | Biomass (kg/ha) |
|---|---|---|
| Original meadow (baseline) | 54–80 | 496–720 |
| Year 1 ploughed | 57–82 | 405–836 |
| Year 5 ploughed | 17–32 | 60–140 |
✅ What protects earthworms?
- 🌾 Mulching — straw mulch supports 2× more earthworms than plastic film
- 🔄 Crop rotation — diverse rotation increases earthworm populations; soy monoculture has 9× fewer than rotated plots
- 🌿 Green manures — organic residues increase annexic/epigeic earthworm biomass 3.4–12.5×
- 🚜 Gentle tillage — shallow, infrequent, avoid spring/autumn mating seasons
- 🧪 Compost not synthetic fertiliser — synthetic fertilisers acidify soil; earthworms prefer neutral pH
❌ What harms earthworms?
- ❌ Neonicotinoids — extremely toxic to earthworms
- ❌ Glyphosate — deep-burrowing earthworm surface activity almost ceases 3 weeks after application
- ❌ Deep ploughing — especially in spring and early autumn
- ❌ Stubble burning — kills surface-dwelling earthworms and their eggs
✨ Summary
The earthworm is free labour in your garden — if you let it work. Mulching, gentle tillage, crop rotation, compost and a chemical-free approach: these are the four pillars of an earthworm-rich, fertile soil. 🪱
🔗 Related articles
- Worm Composting at Home – turn kitchen waste into black gold
- Mulching in the Garden – the power of covered soil
❓ Frequently asked questions about earthworms and soil life
Why does ploughing cause such a dramatic drop in earthworm populations over several years?
Ploughing repeatedly destroys the burrow networks earthworms depend on, exposes deep-dwelling species to predators and desiccation, and physically cuts many worms in half. Each pass also buries the surface organic matter they feed on, so a population that survives the first ploughing is progressively starved and displaced with each following year.
Why does glyphosate reduce earthworm surface activity even though it’s a herbicide, not a pesticide?
Glyphosate disrupts a metabolic pathway found in soil microbes that earthworms rely on as part of their gut microbiome and food source, indirectly starving them, and residues can also directly stress the worms’ physiology, making them retreat deeper into the soil to avoid exposure.
Why does crop rotation support so many more earthworms than a soy monoculture?
A single repeated crop offers earthworms the same narrow range of root residues and chemistry year after year, while rotation delivers a varied diet of organic matter and disrupts the buildup of any one pest or pathogen that might otherwise affect the worms indirectly through soil chemistry changes.
Why does straw mulch support twice as many earthworms as plastic film mulch?
Straw mulch is itself a food source that slowly breaks down and feeds surface-dwelling earthworm species, while also buffering soil temperature and moisture. Plastic film blocks this organic input entirely and can create extreme temperature swings underneath it that earthworms must avoid.