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This content is taken from the Lancaster University's online course, Soils: Introducing the World Beneath Our Feet. Join the course to learn more.

Skip to 0 minutes and 12 seconds There are two approaches that you can use to establish earthworm populations, depending on whether you’re able to dig a hole or not. Dig a hole 20 cm by 20 centimetres and 20 centimetres deep. If you’re using a garden spade, this is often one spade width. Remove this soil and put it into a tray or box. Sort through the soil by hand, removing earthworms carefully as you go. You can count them as you remove them or at the end. Once you’ve counted all the worms, return the soil and the worms to the hole.

Skip to 0 minutes and 57 seconds Measure a 30 by 30 centimetre area of soil. Weigh out around 40 grammes of ground yellow mustard seed. Yellow mustard seed is available from the supermarket, although you may need to grind it up yourself. Add the mustard seed to 4 litres of water and shake well to dissolve it. Pour the water slowly inside the boundaries of your study area, making sure it soaks into the soil. You might have to pause to allow the solution to infiltrate. The mustard solution irritates the worms’ skins, so they’ll come to the surface to get away from it, but it doesn’t harm them. Collect the worms from the soil’s surface.

Skip to 1 minute and 39 seconds Make sure you wait until they’re fully out before you collect them or you may harm them. Put the worms in a bowl of fresh water to wash the solution off, and record how many you have. Put the worms back on the soil surface away from the area you treated.

Practical activity - How many worms?

Earthworms are important for soil formation and health but how many worms are there in the soil?

Watch this video to see two methods for estimating worm numbers. Post your results in the discussion below saying which method you used.

If you want to refer to written instructions, you can download the transcript above.

Safety tips

Please take care whilst digging and handling soil:

  • You will be handling soil. Be wary of sharp objects that may be buried and not immediately visible
  • If you are using a shovel, make sure you are wearing shoes (not barefoot or sandals)
  • Be aware of any biting insects (or other creatures) that may be living in the soil or undergrowth
  • Wash your hands when you have finished
  • Please ensure that you only carry out activities in line with local Covid-19 restrictions

Please check our safety tips in the download section below.

How many worms did you find?

If you are interested in identifying your worms’ species you can find guides online. For example, this is a guide to British worms.

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Soils: Introducing the World Beneath Our Feet

Lancaster University

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