Go Green: Composting With Earthworms

  An earthworm composting kit.

The presence of earthworms is the best indication of the quality of our soil. The recent warm, wet weather has brought earthworms back to the soil surface. The worms favor early summer - they do not like December’s freezing cold or August’s hot dry weather.

Worms are most beneficial. There are over 5,500 named species of earthworms known worldwide. They can be found everywhere except polar and arid climates. They range in size from two centimeters (less than one inch) to the Giant Gippsland earthworm’s astonishing length of over three meters (almost ten feet).

Earthworms eat in a unique way. Their mouth cavity connects directly into the digestive tract without any intermediate processes. Earthworms are decomposers, feeding on leaf and other plant matter.

Earthworm activity aerates and mixes soil. They assist mineralization and nutrient uptake by vegetation. Certain species of earthworm come to the surface and graze on the higher concentrations of organic matter present, mixing it with the mineral soil. Because a high level of organic matter is associated with soil fertility, an abundance of earthworms is beneficial to the organic gardener. As long ago as 1881, Charles Darwin wrote: It may be doubted whether there are any other animals which have played so important a part in the history of the world, as have these lowly creatures

The major benefits of earthworm activity are:

Biological: The earthworm is essential to the process of converting dead organic matter into rich humus. Composting ensures the continuance of the cycle of fertility. The earthworm pulls any organic matter deposited on the soil below the surface (e.g., leaf fall, manure, etc). The worm will use the organic matter for food or when it needs to plug its burrow. Once in the burrow, the worm will shred the leaf and partially digest it, then mingle it with the earth by saturating it with intestinal secretions. Worm casts (see below) can contain 40% more humus than the top 6" of soil in which the worm is living.

Chemical: The earthworm ingests dead organic matter as well and other small soil particles. The worm excretes casts, which are deposited on the surface or deeper in the soil. Castings are a perfectly balanced selection of minerals and plant nutrients that are made available to plants in an accessible form. Earthworm casts are five times richer in available nitrogen, seven times richer in available phosphates and 11 times richer in available potash than the surrounding upper six inches (150 mm) of soil. In conditions where there is plenty of available humus, the weight of casts produced may be greater than 4.5 kg (10 lb) per worm per year. This is why it pays the gardener or farmer to keep worm populations high.

Physical: An earthworm keeps the soil structure open by burrowing. This creates many channels that allow the processes of aeration and drainage. The earthworm not only creates passages for air and water to traverse, but is itself a vital component in the healthy soil, a living biosystem.

One thing is certain, rich fertile soil that is organically cared for, well-fed and husbanded by its steward will reap its reward in a healthy worm population. Denuded, overworked, and eroded land will contain fewer, scrawny, undernourished earthworm specimens.

You can build your own earthworm composting box by following the tips provided by the Savvy Gardener at this link.