I’ve been spending a lot of time recently with the broadfork, preparing new beds for the growing season. As I get a peek at what lies beneath the surface of the soil, I have learned that we have an abundance of earthworms! Of course, I love seeing them because I know it is a sign of healthy soil. Dex loves carrying them around and then placing them back on the soil and putting a little handful of dirt on top of them, exclaiming “Verms! Verms!” with an inexplicable German accent.
However, seeing these big, fat worms, nearly paralyzed by the cold, but still alive made me wonder about them. I had always assumed they had relatively short life spans, knew nothing about their reproduction, and mostly thought of them as little digestive tracts. I am not the kind of person who can wonder about something and not go find the answers to my questions. Thank God I live in the age of the internet, or I would never leave the library. What I discovered surprised me. These are fascinating little creatures, so I thought I’d share some of what I learned.
If only we could be so useful just by pooping…
Earthworms work wonders for our soil, just by defecating. Earthworm poop is called casts. They eat the soil and get their nutrition from the fungi and bacteria in it. While they are carrying on their eat-poop-dig-rinse-repeat lives, they do many lovely things.
- They fragment organic matter and mix it up with the many microorganisms that survive their digestive tract. They thereby effectively increase microbial activity.
- They mix up the soil. They pull nutrients from deep in the soil and deposit it on top. Then they take the organic matter from the top layers of soil and drag it deeper down. According to the NRCS, they will effectively turn over the top 6 inches of your soil in 10 to 20 years all by themselves.
- They aggregate the soil and help give it structure.
- They increase infiltration and water-holding capacity. Earthworm burrows increase the amount of air space, called porosity, of the soil. Therefore, when it rains, more can infiltrate into the soil rather than run off, which improves water quality. The soil can also hold more water.
- They provide channels for root growth. Earthworms provide tunnels that preferentially fill with water and are lined with nutrients. If you were a plant root, where would you go?!
Earthworms have between about 100 and 150 segments, depending on the species. Different segments of the earthworm perform different functions and they have well-developed nervous, circulatory, digestive, excretory, muscular, and reproductive systems. Here are some diagrams of what’s going on inside an earthworm. The first section is, of course, the mouth and the cone-shaped part that helps them push through the soil. One thing I certainly didn’t know is that earthworms are covered in little, retractable hairs, called setae, that help them push through the soil. They also have glands that lubricate their passage through soil.
Earthworms breathe through their skin. I had always assumed that they head out of the soil after a heavy rain because they would drown underground. Apparently, this is not true. They crawl out of the ground when it rains because they are able to stay wet enough (their skin has to be wet to breathe) and it’s easier to find their fellow worms and get it on, or to find another spot with more food.
Speaking of getting it on…
Earthworms are hermaphrodites, but still need other earthworms to reproduce. They lay head to tail to copulate and exchange sperm… *ahem* The clitellum is the conspicuous ring on worms (which changes from pinkish to red-orange when they are ready to mate), and is where the eggs are fertilized and cocoons are formed. The cocoon is then deposited in the soil and about 3 weeks later is the blessed event; anywhere from 2 to 20 baby worms are born. This also signifies the point in the blog post when I am no longer tempted to make gross jokes about worm sex. Lucky you.
Other cool stuff about earthworms
- The thing that really amazed me about earthworms is that they can live to be more than 10 years old! I had never really thought about it much, but assumed they lived for a year or so. I was so surprised to see huge, fat worms in my soil in April, but I guess this is no surprise at all!
- There are 2700 different species of earthworm.
- They can grow to be almost a foot long.
- You can’t cut a worm in half and expect it to become two worms. They can regenerate a lost tail, but if you cut them in half too far up, they might just die.
- Worms can eat their weight each day.
Composting with worms is something I know little about, but I plan to learn. A woman in my Master Gardener class says she just has buckets in her basement where she puts her kitchen waste, and the red wrigglers turn it into soil. I’m planning to get some worms from her and give it a shot. I’ll report back when we see how it works!
Here are some interesting links that I used as resources if you’d like to learn more:
University of Florida Extension: http://edis.ifas.ufl.edu/in047
Penn State Extension (PDF): http://pubs.cas.psu.edu/freepubs/pdfs/uc182.pdf
Colorado State University Extension: http://www.colostate.edu/Dept/CoopExt/4dmg/Soil/worms.htm