Soil Steps

15 August 2026 ยท Field Guide

How to do a simple earthworm count

Nematodes get most of the attention on this site, but earthworms are the soil organism most people can actually identify without a microscope, and a simple spade count remains one of the best available proxies for soil biological activity that a farmer can measure without sending anything to a laboratory. Timing matters more than technique here: earthworms are least active, and least visible, during drought, waterlogging, or frost, so spring and autumn, when soil is moist but not saturated, give the most representative count.

How to do a simple earthworm count, at a glance A five step summary: dig a 20cm pit, search by hand, sort into three groups, record counts, repeat and compare. 1 Dig a20cm pit 2 Searchby hand 3 Sort into3 groups 4 Recordcounts 5 Repeat &compare
The five steps of a simple earthworm count, at a glance.

What you need

The steps

  1. Dig a 20cm by 20cm pit, to a depth of 20cm. Lift the soil out in one block where possible and place it onto the tray or sheet, rather than scattering it across the surrounding ground.
  2. Break the soil apart by hand, searching as you go. Work through the full block methodically rather than skimming the surface, since many earthworms retreat downward when disturbed, and allow up to twenty minutes for a thorough search.
  3. Sort what is found into three ecological groups. Epigeic worms are small, fast moving, and dark, and live in surface litter and organic matter. Endogeic worms are pale, live horizontally within the topsoil, and rarely surface. Anecic worms are large, with a dark head and pale tail, and build permanent vertical burrows deep into the profile, the common earthworm being the best known example.
  4. Record the total count and the split between the three groups. The balance between groups matters as much as the total, since anecic species in particular are sensitive to cultivation and compaction and are often the first group to disappear from heavily worked or trafficked ground.
  5. Repeat at several points and note soil conditions. A single pit gives a noisy result, so three to five pits across a field, alongside a note of soil moisture and recent management, give a far more reliable picture than one count taken at the gateway.
As a rough benchmark, fewer than ten earthworms per pit often points to compaction, low organic matter, or a recent pesticide application worth investigating further, though the figure varies with soil type and season and should be read as a prompt to look closer, not a verdict on its own.

Earthworms are ecosystem engineers rather than a food source for most of the soil food web discussed elsewhere on this site, but their burrows measurably improve infiltration and root access, which links this simple count directly back to the erosion and structure assessments earlier in this series: a field scoring poorly on VESS and showing few anecic worms is very often the same field showing surface capping and runoff after rain.

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