Earthworms are an indicator of biological life in the soil, large and small. Easily visible and easy to count, higher numbers can be an indicator of improved soil health. Avoid carrying-out during extreme weather conditions eg: very dry, hot or cold, or in the following few weeks after a manure/compost application.
It is best to count earthworms in early Autumn or late Spring.
Want to learn to identify the 3 different types of earthworms?
This earthworm guide from AHDB is also helpful.
Hand Sort Method (5 mins per hole)
- Bin bag/tray
- Dig out a square as wide as your spade, and dig down about 20 cm (or as deep as is possible on your land, you just need to be consistent across your farm). Overall size: ~20 x 20 x 20cm
- Place the dug up soil on the plastic bag.
- Break down the soil with your hands, keep any earthworms you find on the bag. Put all broken down soil back in the hole.
- Count the number of earthworms and record in the app.
- You can stop there and press ‘save’ in the app…Or…
- You can next separate the earthworms into adults and juveniles, putting the juveniles back in the hole.
- Count the number of leaf-litter, top-soil and deep earthworms and record the number of each type in the ‘notes’ section below where you entered the total number of worms, and ‘save’.
- Put all earthworms back in the hole.
- Number of earthworms you find as soil broken down.
- Make a ‘note’ on the app of how many adult leaf-litter, top-soil and deep earthworms there are.
Types of Earthworm (from AHDB and Jackie Stroud guide)
Alternative: Mustard Extraction Method
- Quadrat (177cm pipe/rope) – 0.25m2
- Mustard water (pre-mixed, night before)
- Bin bag
Preparing Mustard solution:
- Fill a 1.5l bottle half full of warm water
- Measure a tablespoon (15g) of English mustard powder
- Using a funnel, pour the mustard powder into the bottle
- Mix the solution thoroughly
- Fill the 1.5l bottle the rest of the way with warm water
- Let sit overnight
- Place quadrat on ground
- Remove leaf litter/cut-away excess grass growth
- Pour half bottle (~750Ml) of mustard solution over the ground within the quadrat
- Remove worms as they emerge, place on plastic bag
- Wait a couple of minutes or so
- Repeat step 3
- Remove all remaining worms
- Record the total number of worms collected
- Total number of earthworms