6/22/2002

Rocky Mountain News

By Dale Langford

Over the last two weeks, through digging and rototilling, I noticed some profound but easily explainable differences in the earthworm population in my gardens.

Turning over a new area that was previously in grass sod yielded the typical heavy clay, highly alkaline generally undesirable soils of our area. It also yielded only a rare and puny earthworm. Moving 2-year-old compost to add to this muck was a joy; in went a few fat nightcrawlers and even more regular-sized earthworms and some smaller varieties.

So what's the big deal with earthworms? Though them might leave some yards bumpy and uneven, a good supply of earthworms is a most desirable thing in your home landscape.

These remarkable creatures are one of nature's most efficient earth movers. If we can loosen special areas of our landscape and get enough organic material incorporated into it over a period of years, the earthworms can literally replace your tiller. Here are some of the benefits of encouraging earthworm numbers.

Because of their unique digestive system, worms enhance the organic material they digest. As soil, leaf pieces, grass blades and any other organic material passes through their remarkable intestines, it is converted to a “casting” that makes a much better soil structure. They get help from unexpected sources. Other soil organisms like bacteria and protozoa line the worm's gut and live out a symbiotic (one dependent on the other) existence helping to break materials down to their basic elements.

Nutrients that start out insoluble or only partially available are transformed to simple compounds that roots gobble up. Nitrogen, phosphorous and potassium in soil complexes are converted into forms that are good for gardens. In the process, the castings emerge sort of “glued” together that give previously heavy clay a much better structure. Air and water moves more easily through the earth, and these two elements are the key to any living soil. The tunnels or burrows made by earthworms also serve for increased air and water movement.

How much use could these small creatures have? In fact, measurements have been taken that are quite astounding. In rich farming land, up to 1,000,000 earthworms per acre can live in the top soil. Since each worm produces its own weight in castings every day, this adds up to moving a lot of material. At this rate, enough “new” soil could be produced over a four year period to add a couple of inches to each acre.

Earthworms are nocturnal creatures coming to the surface in the cool, moist night. They have no lungs but ``breathe'' through the moist surface of their skin by an oxygen exchange process. As the worms surface at night, they pull leaves, grass blades and other pieces of organic mater down into their burrows for food. These same soil tunnels pose a danger for them in heavy rain. That's when they all pile up to the surface to get some air. The excess water running their burrows full doesn't contain enough oxygen, and the worms can easily suffocate.

You can always buy worms and add them to your soil in hopes of improvement but don't hold your breath. An easier way is to increase the organic matter and the worms will soon discover it themselves. Continue adding mulch, leaves, peat, manures or compost, and your resident population will keep increasing, as will the quality of the soil.