Hardworking Earthworms

Increase the number of earthworms in your garden for more vibrant and prolific plants.

| September/October 2016

Charles Darwin, who was fascinated with earthworms, wrote, “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.”

Worms have made the soil of many nations fertile, and they will do the same for your soil. Having thousands of earthworms in your garden is like having a thousand tiny tillers running day and night, and each tiller is pulling a compost spreader behind it.

Earthworms mix the soil as they eat their way through it, and their tunnels help loosen compacted clay or silt, allowing water to seep through. This also helps increase aeration of the soil, sometimes up to 75 percent, which in turn allows the tiny organisms around your plants’ roots to thrive. (However, earthworms are not good for some northern gardens; more on that in a minute.) Earthworms recycle nutrients and disperse them through their castings, making them more available to plants. Earthworms will do this work for you all day and even while you sleep. What’s not to like?

Black gold

Earthworm castings are as good as gold to a plant. As worms eat their way through the soil, they devour organic material and soil, and inside the worm’s crop and stomachs, the organic material is broken down into nutrients while the soil is ground into extremely fine particles. This “soil soup” in the worm’s gut mixes with beneficial microorganisms from inside the worm, and nutrients that would otherwise be difficult for plants to absorb are made more readily available when excreted.

USDA tests show us that castings compared to the soil from which they were made have about five times the available nitrogen, seven times the phosphorus, three times the magnesium, eleven times the potassium, and one and a half times the calcium. Even the slime on the earthworm is high in nitrogen. That nitrogen is the reason when you dig up a plant, the roots have wrapped around the earthworm burrows. The burrows also help catch fertilizer runoff and bind it to the soil to keep within reach of plant roots.

The worms in an acre of land can produce up to 700 pounds of castings in a day. Imagine how much 700 pounds of fertilizer would cost. What’s more, according to Dennis Linden, a USDA Agricultural Research Service scientist in St. Paul, Minnesota, worms can create roughly 250 miles of tunnels per acre every week, allowing for better aeration and better rain absorption.

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