The Dirt on Earthworms

By Tina Patterson

Like Rodney Dangerfield, the lowly earthworm gets no respect. Yet, this seemingly unimportant lumbricid is an indicator of soil health, and can dramatically impact soil structure, water movement, nutrient dynamics and plant growth. There are 21 different species of earthworms in Michigan, and 50-300 worms can be found in a square yard of cropland nutrient-rich soil.

Earthworms are made up of many small segments, each segment with many small hairs that assist the worm in movement, aided by a slimy mucus that it produces. Without a skeletal system, the worm is heavily muscled. The blood circulating through its system gives it a reddish color. Earthworms can live up to eight years, but most do not survive more than a year.

Moist soils are necessary for earthworms to thrive, and the majority of worms are found in the top meter of soil, most often just below the surface where there is plenty of decomposing plant material. Earthworms consume dead and decaying plant material and are prey to robins, red-winged blackbirds, crows and other ground-feeding birds as well as foxes, shrews, skunks, moles and garter snakes. During droughts or winter freeze, earthworms may go deeper than the top meter of soil. Worm tunnels have been found at depths of 16 feet.

Earthworms promote a healthy environment in the following ways:

• Worms eat microorganisms and produce organic matter in their feces or casts that becomes plant food.

• Casts help move large amounts of soil to the surface and carry organic matter to the lower strata.

• Earthworms help with soil drainage, acting as a conduit for rain, especially after a heavy downpour. These burrows minimize soil erosion and increase porosity and drainage.

• By fragmenting organic matter and increasing soil porosity, earthworms increase soil water retention ability.

• Channels made by earthworms are rich in nutrients and provide space for root growth. This makes it easier for plants to set a deep root base.

• As earthworms eat the plant and crop residue, the castings they leave behind provide nutrients to the upper soil levels and the surface residue is pulled into their burrows.

Earthworms are more than good fish bait; they play an integral part in keeping soil rich with nutrients and maintaining a healthy environment for farms, fields and forests. So the next time you see a worm crawling on the sidewalk after a heavy rain, give it some respect.


7 thoughts on “The Dirt on Earthworms

  1. Earthworms are good for gardens, I’ll give you that. It’s just that Michigan was earthworm free from the last glaciation until European settlement. Therefore, our natural ecosystems are adapted to function without earthworms with other species such as ants serving as our soil nutrient mixers. Earthworms turn over leaf litter much faster than our native soil cultivators. The resulting abundance of bare soil surfaces tips the balance in favor of invasive weeds such as garlic mustard over the native wildflowers such as Dowagiac Wood’s beloved blue-eyed marys, which have spent the last 10,000 years adapting to germinating in the presence of leaf litter.

    • Invasive weeds only thrive on sub-optimum and unbalanced soil. Why not cover the bareness and assist your straggling survivors ?


  2. Pingback: The Dirt on Earthworms (via Michigan Nature Association) « Custom Gifts By J. C. Hale

    • Without our lowly earthworms my organic ingredients wouldn’t be worth a hill of beans? 🙂 Here is Ravensdale, WA. our lot is full of rocks, we have been working on improving what little soil we have, and since we have several composting areas in our yard our worm population has been growing slowly. We have also transplanted several azaelia bushes which came with their own earth worms so I know our hill soil is definitely on the way to improving ten fold just because they have been doing their jobs with helping on the erosion control by improving root struictures n nutrients being added to our alkaline ph from mostly alkaline to almost perfect acidity/ alkaline base.
      Keep up the good work on how the poorly rated disrespected earthworms! LOVE THEM LITTLE CRITTERS 😛

  3. Pingback: Mich Enviro Report: Birds, Earthworms, Rain & the Rifle River « Mr Great Lakes

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