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Careful! Earthworms Underfoot

Worms Help Farmers With Gardening.

Graphic of worm wearing farmer's hat and overalls.

A soil scientist for the past 25 years, Dr. Dennis Linden knows a thing or two about earthworms.

Sure, he knows worms are good for gardens and farmland. By tunneling through soil, they bring in oxygen, drain water and create space for plant roots. Like many people, he also knows worm “casts” (manure) are rich in nutrients.

Linden works at ARS’ Soil and Water Management Research Lab in St. Paul, Minn. There, he is literally unearthing important clues farmers can use to get the most from their land’s earthworm population.

Along the way, he’s come across some less well-known facts about these helpful creatures, such as how well they adapt to different soils and temperatures.

Two good examples are species of Aporrectodea and Lumbricus [say, “Apor-wreck toadeea,” and “Lum brick-us”].

When temperatures drop or soils get too warm or dry, these worms know what to do. If it starts getting chilly, they may tunnel deep into the soil before it hardens. They may also coil into a slime-coated ball and go into a sleep-like state called estivation. It’s something like a hibernating bear.

Worm Cocoon

Photo of a worm cocoon that resembles smooshed kernels of corn.

One winter day, Linden chipped away at a frozen patch of soil to check on these slimy, sleeping beauties.

I “found them curled up in a tight little ball with a layer of mucus around them,” says Linden. “They’re very well adapted. They’ll survive in frozen or dry soils by estivation and come back when conditions improve.”

Photo of two researchers in a plowed field checking the soil for worms.

Today's farmland is a favorite home of worms whose descendents most likely came with European Settlers. Here, two scientists try their hand at nabbing a modern day descendent.

This adaptability is one reason why species of Aporrectodea and Lumbricus are the most common in North America.

But it may surprise you to know that neither are originally from this country. Scientists believe the worms probably were brought here from Europe by settlers. Most likely “they came with the settlers in ship ballast, seed stock, potted plants and who knows what else,” says Linden.

Once in the New World, as it was called then, these “stowaway” worms grew used to the new soils, climate and plant life. And, they began to spread. In fact, scientists believe the stowaways may have edged out native worm species from the choicest food and soils.

One modern-day descendent is the nightcrawler. Widespread throughout North America today, nightcrawlers are among the country’s largest worms, reaching 8 inches or more.

They are also really fast.

You’ve probably discovered this first-hand if you’ve tried to nab one peeking out of its hole. Nightcrawlers spend a lot of their time on the soil surface getting a snack. So speed is important if they are to escape watchful birds and other hungry predators.

Night crawlers are important to agriculture. But is a bigger worm better than a smaller one, like the common grey, when it comes to mixing soil or making more nutrient-rich casts for plants?

Animated graphic of a cartoon worm racing from right to left.

“Not in my opinion,” says Linden. “I think it has little to do with the size of the worm.” But there’s some disagreement on the topic, he adds.

Each species is different, he says, with different strengths, weaknesses and roles to play in agriculture.

Now, if you’re going fishing, a plump, juicy nightcrawler may be the way to go.

Linden admits to occasionally baiting a hook with the hefty wriggler: “I’ve used nightcrawlers and redworms.”

Animated graphic of a worm crawling on the back of a bird and then diving off of its beak.

--By Jan Suszkiw, Agricultural Research Service, Information Staff

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