Digging up the Dirt on Earthworms
When talk comes up about the garden, it is usually about the flowers; what can be added, what can dead headed and what can be divided. All of this is stuff that needs to be done up on the surface of you garden, but how does the garden work down below? What is it that makes the soil work for the plants? Well, that would be worms. As unpleasant as they may be, they are what make the soil “tick” if you will. In fact there are about 2700 different species throughout the world that all do the same job…basically, making food for plants. It’s a dirty job, but someone has to do it.
 In North America, the most popular worm is the grey-brown night crawler (Lumbris terrestris). These are the guys you see on the sidewalks when it rains and also the ones the Robins get every morning. In Australia they have a worm there that can reach up to 3 meters long! I would hate to be there when it rains. Here we only have to worry about ones that will only reach about 12 centimeters long, which is good, because there can be up to 50 worms per square foot of soil; each one producing its own weight in castings (excretement) every 24 hours. This is the reason they play such a large role in soil enrichment. Worms are not picky eaters, they will not discriminate between dead plant material and dead animal debris, as long as it can be sucked into their gizzard to be broken down for digestion in the intestines and ultimately discarded. PLEASE NOTE: compost, however, should only ever contain plant material. The microorganisms in compost is incredibly complicated which is compromised by adding any kind of animal debris. Really, all they do is eat and dig tunnels right? Right. Wrong. Right and wrong. Theses two basic functions do more than meets the eye.
 Night crawlers are usually found just under the soil’s surface (about 6-12 centimeters deep). Their tunneling helps aerate the soil which not only allows oxygen down to the roots, but also increases water percolation. Both of these things together help in aggregating the soil, which ultimately helps plants uptake oxygen and water. Tunneling is usually done during the day for these guys because the moisture in the soil helps to keep their skin lubricated so they can both move and breathe. The Suns’ ultraviolet rays will quickly kill a worm by drying their skin which suffocates them, which is why these guys wait until night to come to the surface to feed on any organic debris hence the term…night crawler. Also this is when their bird predators are asleep. Castings are left up on the surface at night and raw organic material is dragged down into their tunnels to digest during the day. Worms reproduce by laying eggs. Although each worm possesses both male and female sexual parts, it takes two of them to fertilize each others’ eggs. They will then lay a capsule that hardens into a cocoon which will produce two worms. This can happen up to five to six times per season until it starts getting cold and they then burrow down beneath the frost line to overwinter and wait to start the process all over again next spring.
So, when it rains, the nutrients from the excrements are washed down into the soil (which is aerated thanks to these critters). What were once raw, unaccessible nutrients for plants, is now nutrient-rich tea, available for root up-take. Cultivating every few weeks will assist in folding in the new organic material with the old and keep the soil aggregate for water percolation. You can help keep your night crawler numbers up by working in the middle of the day when they are burrowed deep. This will help avoid digging them up because, contrary to popular belief, they cannot turn into two if cut in half…they die. Also, keep from over watering or you’ll just be feeding the birds.
Remember: worms = nutrient-rich soil = happy plants. If you’ve got worms, you’ve got happy soil.
Written by: Dianna Dawson 2008 |
