I would like to do a simple DIY soil earth worm counts in my vegetable garden beds. What is the best time in the year to do this test? what should the temperature of the soil be when performing this experiment. Some people recommend using mustard powder for this test. Is it necessary? Could you please recommend an easy way to do this test?
Thanks so much for your help.
Thank you for contacting the Toronto Master Gardeners with your question regarding earthworm counts. The presence of earthworms is one indication of good soil health. Soil texture (e.g., clay, sand, silt), structure (the arrangement of soil particles – e.g., size of soil clumps, porosity to water and air, amount of organic matter), soil pH and chemical components of soil are also important. The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) suggests a rough estimate of 10 worms in a shovel-full of earth reflects good soil http://www.omafra.gov.on.ca/english/crops/field/news/croptalk/2017/ct-0917a6.htm.
The link below form Michigan State University provides detailed instructions for earthworm sampling and points out that soil conditions (e.g., dry vs wet and sandy sand vs clay) can impact the number of worms present in a sample. Sampling a few times throughout the growing season and averaging the number of earthworms is recommended. https://www.canr.msu.edu/news/earthworms_can_be_an_indicator_of_soil_health
In agricultural settings, chemicals were used historically to flush out the deepest earthworms in a hole that had already been counted. Mustard water does the same thing but doesn’t harm the worms or the soil. You can find out more about mustard water here https://www.earthwormwatch.org/blogs/why-do-we-use-mustard-water.
Earthworm counts is a fun project for the interested gardener. Results should be considered in conjunction with other indicators of healthy soil (e.g., lots of organic material, good drainage, balanced nutrient content and absence of toxins).
Best of luck with this project!