How Earthworms Benefit Your Soil

How Earthworms Benefit Your Soil

As kids, we either played with earthworms or ran away shrieking at the sight of one. As adults, we have learned that earthworms should not be played with or feared, but they are in actual fact, the gardener’s best friend. Earthworms benefit your soil in many ways.

Yes, the humble earthworm is the best soil conditioner as well as plant food producer (from their excrement called “castings”). Plus they do all this for free! Improve your garden soil and grow healthier plants with the help of earthworms.


There are thousands of species of earthworms the world over, but in temperate regions, only a handful of species are considered to be important for cultivation. Four common types you might encounter in the soil are:

  • The common field worm
  • The green worm (which is a little greenish in color)
  • The night crawler (mainly active at night)
  • The manure worm (also called red wrigglers).

The common field worm is the type with the pronounced “clitellum” (an enlarged segment out of the many on its body) and often encountered in areas with poorer soil. The manure worm is encountered in compost heaps, and it moves a lot if disturbed. They can only survive in soil with very high organic matter or in compost heaps, but they do a great job of breaking down your compost for you.

earthworm in the open

Better Drainage and Air Circulation

Earthworms tunnel their way around under the soil in search of food and moisture. These tunnels create small channels in the soil for water and air to travel in. Rainwater makes its way through the channels to reach plant roots and so does air. The tunnels also allow the excess rainwater to continue to move through the soil so that garden plants are not sitting in soggy soil.

Improved Soil Structure

Clay or compacted soil can be greatly improved with the introduction of earthworms. The tunnels created by the earthworms reduce compaction and make the soil loose so plant roots can expand in search of food and moisture.

Rainwater tends to pool on top of clay or compacted soil. Because the soil is so dense, it can’t absorb the excess water. The earthworm tunnels give water a place to travel so the pooling of excess rainwater does not occur. Notice in dry regions the hard compact soil cannot grow plants, in part due to a lack of earthworms.

Increased Fertility

Earthworms are omnivorous, eating anything they can find, such as decaying roots, leaves, all dead plant matter, fungi, bacteria, nematodes and protozoans. Basically, they eat the soil and then leave behind castings in their underground tunnels. These castings are worm manure and rich in nutrients that will increase the fertility of the soil (which your garden plants need).

earthworm casting
Earthworm casting

Your garden plants feed off from the soil. The more nutrients in the soil, the healthier the plants will be. The castings and the bodies of dead earthworms are rich in nitrogen which gives plants energy to grow. In addition to nitrogen, worm castings also contain phosphorus, potassium, and magnesium, making it the ideal organic fertilizer for the garden.

Invite Earthworms to Your Garden

To increase the earthworm population in the garden soil, stop tilling the garden with machinery. Do only the minimal amount of digging and soil turning possible so worms won’t be killed and their homes destroyed. Tilling exposes the soil to sunlight and oxygen. These destroys the soil organic matter that the earthworms feed on.

earthworms from a no-till field
Earthworms from a no-till field.

If you have no choice but to till your soil, then try to add back some organic mulch afterwards to replenish the lost organic matter. This will encourage the earthworms to return. A layer of compost/organic mulch, or basically any ground cover like wooden planks/bricks kept on top of the soil will keep the soil cool and make it more inviting for earthworms. For winter, any form of mulching helps earthworms survive the freezing conditions.

wooden slabs
Wooden slabs placed on the ground as mulch will encourage earthworms as well as other small garden fauna to hang around underneath them.

Stop using all chemicals and only use organic products in your garden. Chemical pesticides tend to upset the ecological balance of the micro-habitats in your garden, of which the earthworm is a part of.

Not willing to go the slow route? Purchase earthworms at the local garden supply store and add them to the soil. This will get your earthworm colony off to a good start. Also add manure worms to your compost heaps to hasten their decomposition. But remember, unless you are able to get the conditions right for earthworms to flourish, artificially adding them in won’t work in the long run.

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