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Earthworms — A Gardener's Best Friend | Summer 2007 Out Here Magazine

Tunneling earthworms loosen and aerate the soil, making it easier for plants to push their roots through.

Improve your soil by attracting these mighty invertebrates

By Amber Stephens
Illustrations by Tom Milner

Earthworms may be tiny and rarely noticed, but when it comes to turning fallow soil into fertile ground, earthworms are ecological powerhouses. From aerating the garden to adding nutrient-rich castings, or manure, these burrowers have proven their worth as a gardener's best friend.

As worms tunnel through the ground, they loosen and aerate the soil, making conditions easier for plants to push their roots through.

"They're creating air passages, as well as water passages," says Kelan Moynagh, owner of Yelm Earthworm and Castings Farm near Yelm, Wash., among the largest worm farms in North America.

While sliding through these natural drainage ditches, the earthworms' coelomic fluid, the sticky mucus that coats their bodies, and the bacteria in their castings attach to the surrounding soil, causing soil particles to bind together. These aggregates help prevent soil erosion and aid moisture retention.

Their tunneling also helps prevent soil erosion, particularly in soils with high clay content. Clay dirt doesn't absorb rainfall quickly, resulting in soil washouts. But tunneling earthworms create channels through the soil, allowing water to soak deeper into the soil and retain moisture.

Most gardeners, however, value earthworms for their waste. As they consume organic material, not only do they promote decomposition, but they also provide castings, which make outstanding fertilizer.

As mega-eaters, consuming up to their body weight each day, 1 pound of earthworms can convert 1 pound of organic matter per day into earth-friendly castings one bite at a time.

"Once the worms touch that stuff, it turns it into black magic," Moynagh says. This "black magic" is higher in calcium, nitrogen, phosphorus, and potassium than surrounding soil.

Up to 1 million earthworms can live in 1 acre of good soil, typically within the top 18 inches of ground. But without a scientific survey, how do you know whether you have worm-healthy soil?

One sign that your ground lacks worms is an unproductive garden, Moynagh says. Other clues: lots of harmful fungi and a disease-prone garden with plenty of predatory insects.

If your soil isn't crawling with earthworm activity, there are steps you can take to attract them. "Once you start adding organic matter to your garden, the worms will come, no doubt about it," Moynagh says.

Organic matter can include compost, plant litter, mulch, and other natural additions. If you don't have a compost pile, throw your plant-based kitchen scraps — salad scraps, potato and banana peels, coffee grounds, etc. — directly on your garden spot.

Worms thrive on moisture, so water down your garden spot periodically, especially during periods of drought.

Worms also don't like to be disturbed, so avoid soil compaction, tilling, or plowing, Moynagh says.

Keep herbicides and fungicides to a minimum, too, he advises, or "you will be guaranteed to drive worms away."

How do you know if your efforts have worked? Dig a spadeful of soil and sort through it. Most likely, you'll find worms, cocoons, and burrows — proof that these tiny ecological powerhouses are working hard for you.

Amber Stephens is a freelance writer and editor from Amanda, Ohio.