A high density of earthworms is an essential component for healthy soil. Worms decompose matter, recycle nutrients and burrow, increasing soil organic matter content, creating pores for healthy root systems and enabling better water infiltration. Low worm counts can give an indication of issues like compaction, organic matter depletion and waterlogging.

  1. You will need a spade, and if interested in learning the different types of worms, you can print a worm guide from OPAL website.
  2. Warm days when the soil is moist in spring and autumn are ideal for earthworm assessments. When the soil is very dry or cold, worms move deeper.
  3. Dig out five blocks of soil 20x20cm and approximately 30cm deep from a variety of places across the field. This is because worm distribution can be patchy, and it helps average out the counts.
  4. Sort carefully through each sample, counting the worms.
  5. An average of 10 worms is good; 15 and above is excellent.

Searching through a spadeful of soil for worms © GWCT