How to do a health check on your garden’s vital earthworm population

IN MOST parts of the world, earthworms are seen as the gardener’s friend because of the many ways they improve the soil. Worms feed on decaying organic matter and their faeces contain soil nutrients, such as nitrogen, phosphorus and potassium, in forms that are easier for plants to take up. Their tunnels also improve drainage and give a lighter, more airy structure to soil.

Ecologists may use the number of worms in a patch of earth as an indicator of whether soil has a good pH, sufficient organic matter and isn’t too compacted. Gauging this in a standardised way involves …