Earthworms are a key indicator and driver of soil health. Populations increase dramatically under zero-till regimes and are crucial to the soil rehabilitation process. Their burrows create drainage channels, aerate the soil, and their casts improve fertility.
Population Data by Tillage System
Terbrugge Data (comparative)
| Tillage system | Population (worms/m²) | Biomass (g/m²) | Burrow volume (10cm³/m²) | Earthworm ejection (kg/m²/year) |
|---|---|---|---|---|
| Conventional (ploughed) | 25 | 18 | 10 | 1.4 |
| Reduced tillage | 36 | 45 | 24 | 3.5 |
| Zero-tillage | 153 | 147 | 110 | 11 |
Key insight: Reduced tillage is only marginally better than conventional ploughing. The major difference comes from eliminating tillage entirely. Worms create their burrow systems over years — they need continuity.
[Source: dd-issue-01, 2026-04-11] (Source: F Terbrugge)
Tony Reynolds — Thurlby Grange Farm, Lincs
- Tony’s zero-till soil: 47 worms per sample
- Neighbouring field (same soil type, ploughed annually): 1 worm per same volume
- Farm average: 80–90 worms/m²
- Target: 140–150 worms/m²
[Source: dd-issue-01, 2026-04-11]
Biology Notes
- Earthworms are hermaphrodites (both male and female organs; segments 9–15)
- Mating: heads pointing in opposite directions; sperm exchanged and stored in sacs
- Eggs laid ~27 days after mating
- Populations can double in 60 days under ideal (worm farm) conditions
Ecological Role in No-Till Systems
- Create biopores → improve drainage, particularly important under heavy rainfall events
- Distribute organic matter through the soil profile
- Consume and shred crop residues, accelerating decomposition
- Casts improve soil aggregate stability
- Burrows provide channels for deep rooting
[Source: dd-issue-01, 2026-04-11]
Earthworms and Slug Control
Under zero-till, worms assist slug management:
- Worms eat slug eggs → high worm population reduces slug egg survival
- Ground beetles (also more abundant under no-till) eat more slug eggs when worm populations are high
- Creates natural balance — reduces or eliminates need for slug pellets
“There’s a balance created naturally, rather than a dependence on pelleting.” — Tony Reynolds
[Source: dd-issue-01, 2026-04-11]
#30MinWorms — National Earthworm Survey (Jackie Stroud, Rothamsted)
Jackie Stroud (Rothamsted Research) developed a citizen-science protocol for farmers to assess earthworm biodiversity on their own land.
Three Ecological Groups
| Type | Size | Colour | Role |
|---|---|---|---|
| Surface worms (epigeic) | Small (matchstick) <8cm | Red | Break down surface litter; food source for birds |
| Topsoil worms (endogeic) | Small–medium | Pale (grey/pink/green) | Mix and aggregate soil; mobilise nutrients for plant uptake |
| Deep burrowers (anecic) | Large (pencil) | Heavily pigmented (red/black head) | Vertical burrows up to 2m; water infiltration; deep rooting |
Key diagnostic: if any type is absent or rare, it indicates potential over-cultivation or under-feeding of the soil.
#60MinWorms Pilot (Spring 2018) — Results
- >1,300 ha surveyed by farmers across the country
- Average: 9 worms per 20cm³ pit (standard protocol: 10 pits per field)
- High numbers (>16 per pit) were rare; best fields: 27 worms per pit
- 42% of fields may be at risk of over-cultivation — indicated by absence/rarity of surface (epigeic) and/or deep-burrowing (anecic) earthworms
- Earthworm counting alone is not a reliable indicator of biodiversity — species identification is essential
- Tillage had a statistically significant negative impact (p < 0.05) on earthworm populations
- Organic matter management alone did not mitigate tillage impacts
- Recruitment channels: Twitter and Farmers Weekly most effective
Streamlined #30MinWorms Protocol
- 5 pits per field (reduced from 10) — each 20cm x 20cm x 20cm
- W-shape sampling pattern across the field
- Hand-sort for 5 minutes per pit
- Identify adults by type (surface/topsoil/deep burrower)
- Check for pencil-size vertical burrows and surface middens (indicators of deep burrowers)
- Farmer fieldwork cost: approximately £1.48/ha
- At national scale: £14 million could be saved versus professional surveying by using farmer participation
[Source: dd-issue-03, 2026-04-11]
Andrew Mahon Earthworm Data (Bromborough Estate)
Single-field comparison on Hanslope clay:
| Treatment | Worms per unit area |
|---|---|
| Min-tilled + Cross Slot drilled | 17 |
| Ploughed | 5 |
| No-tilled (2 years) | 27 |
[Source: dd-issue-03, 2026-04-11]
Implications for Drill Design
- High earthworm activity creates a self-cultivating soil with existing biopores
- Drills that disturb minimal soil preserve the worm burrow network
- Autocasting (broadcast seeding behind combine) works well on established zero-till land because the surface is fertile and friable — worm-worked topsoil
[Source: dd-issue-01, 2026-04-11]
Related Pages
- Conservation Agriculture — Core Principles — minimum disturbance principle
- Tony Reynolds — field-measured worm count data
- Soil Carbon and Organic Matter — earthworms as carbon distributors
- Mycorrhizal Fungi Under No-Till — other soil biology in no-till systems
- Blackgrass Management Under No-Till — earthworms and slug ecology interaction
- Andrew Mahon — Bromborough Estate, Northamptonshire — Earthworm counts under different tillage on same field
- Soil Health Monitoring — In-Field Tests and Tools — Earthworm counting as part of soil health assessment
- Soil Farmers of the Year 2018 — Will Steel’s worm count increases (12M→15.3M/ha)