All photos courtesy of Danita Cahill Earthworms are definitely the movers and shakers of the soil world. Ravenous creatures, even without teeth, earthworms can eat half their body weight every day. Since an adult night crawler, Lumbricus terrestris, may reach a weight of 0.39 ounces, that adds up to approximately four and a half pounds of soil consumed, digested and recycled by a single adult nightcrawler each year. The Good The number of earthworms per acre depends on the type of soil. The number could be a hundred, or might even number into the hundreds of thousands per acre. For the farmer, that equates to a whole lot of soil movement. The resulting worm feces – or, in more polite circles, worm castings – is a good thing. Once organic matter has worked its way through a worm, the nutrients in castings are much easier for plants to absorb and utilize. Earthworms also help aerate the soil with their tunneling. Worms are most active during the spring and fall months, and live in various layers. Shallow-dwelling earthworms live in the top 12 inches of soil. They create random pathways as they feed. Deeper dwelling earthworms live in lower levels of soil – as deep as 6.5 feet. Their burrows are semi-permanent. Shallow dwelling worms are the most beneficial to the top soil. Not only do their burrows allow the movement of air, but also the movement of water. In areas of compaction or overuse, such as land developed by urbanization, or heavily-farmed land, the worms’ movement through the soil is especially important. Nightcrawlers are surface feeders, coming up from their burrows at night to feed. They also store snacks for later. They are the only earthworms known to pull bits of leaves and plant debris down into their burrows where it further decomposes before they ingest it. Worm populations often increase under reduced tillage systems, according to results from tests conducted in Indiana and Illinois tilled and untilled corn and soybean fields. Worm Biology Earthworms have no skeleton. The earthworm’s digestive system is a tube running from the mouth to the rear of the body. Consuming and digesting organic matter, such as fallen leaves, allows worms to move nutrients such as nitrogen and potassium from the surface down into the soil. Worms have a simple nervous system – cutting a worm in half does not seem to unduly stress it out. However, contrary to popular belief, most worms chopped in two will not grow into two separate worms. If the head portion is long enough, it may grow a new tail and continue to live, but the tail portion will not grow a new head, or new internal organs, and will eventually die. Earth worms have no lungs, instead they breathe through their skin. This process is known as diffusion. A worm’s skin must stay moist to keep diffusion working. Too much moisture, such as water saturated soil from heavy rainfall is also detrimental to worms. It doesn’t allow gases to diffuse across the worm’s skin. In such a case, if the worm doesn’t surface, it will suffocate. In Germany, night crawlers are known as “rain worms.” An earthworm’s head is at the thicker, rounder end. It has no eyes or ears, but in addition to a toothless mouth it has Continued on Page 24 22 <strong>Organic</strong> <strong>Farmer</strong> <strong>February</strong>/<strong>March</strong> <strong>2020</strong>
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