A Guide to Earthworms
Most people see an earthworm and think 'ugh'.
Little do they realise what a good job the little worm is doing for them.
Read on and find out a lot more about the earthworm.
The scientific bit
The earthworm or to give it its proper Latin name Lumbricus terrestris, usually grows to about 10 in. long, and 0.4 in diameter. Earthworms are usually reddish in colour, since their blood carries a reddish pigment. Worms are very important to the soil, since their burrowing causes more air and water to reach deeper into the ground. They also feed on decaying organic material and the soil around it, and deposit the waste products, called castings, on the ground, which is mostly soil filled with nutrients, which enriches the soil around it.
In studies made of the earthworm it has been found that if one inch of organic material is placed on the surface of the soil with a relatively healthy earthworm population, it would be digested within a few months.
Charles Darwin estimated that if an acre of good soil contained 63,000 earthworms, they would deposit 2 in. of new top soil every 10 years.
Habitat
Although earthworms are most numerous in the top 6 inches of soil, they also work in the subsoil. Most earthworms make their tunnels at least a meter deep..
They must have a moist environment in order to breath, and therefore, if the soil dries excessively, the worms will burrow deeper or move to another location. Recycling of organic material is much faster in areas of higher rainfall.
They tolerate a range of temperatures from 0-35C. Earthworms cannot regulate their body temperature and will move to a shady location or deeper in the soil during hot weather.
They are basically nocturnal; they come to the soil surface at night when temperatures are lower and humidity higher.
Earthworms live in almost all soil types, except very coarse soils (sands) and those that are very acidic, bringing mineral rich soil from below to the surface. This adds to the supply of nutrients available to the plants. Research shows that in 100 sq. ft of garden soil, earthworms may bring from 4-8 lbs of dirt to the soil surface each year.
Feeding habits
Some gardeners feel that earthworms are harmful to the soil; in fact, the opposite is true. As earthworms tunnel through the soil, they feed on the partly decomposed organic material and ingest the soil. The organic matter that earthworms eat consists of decomposing plant material and animal parts; as well, they eat soil micro-organisms such as bacteria, fungi, and nematodes. Earthworms will feed on roots or other parts of plants that have been decayed by other organisms; but they do not feed on healthy plants. In the earthworm, the organic matter is broken down further and after it is excreted (as "castings") it is easily converted by micro-organisms in the soil to nutrients, that are taken up by developing plants.
Reproduction
Reproduction in earthworms is not fully understood. For most types, some mechanism stimulates the worm to produce a cocoon which is deposited into the soil. One or more live worms eventually emerge from the cocoon. They reach sexual maturity in 3-6 weeks. Some species can regenerate amputated body parts but no known species, if cut in two, can generate two viable worms.
General
Besides incorporating any organic matter into your soil, earthworms are good manufacturers of fertiliser. Castings have a high nutrient and organic matter level much higher than that of the surrounding soil. Each day they produce nitrogen, phosphorous, potassium and many micro nutrients in a form that all plants can use.
Not only do they produce this fertiliser but they spread it thoroughly within the top 12 inches of soil. A soil that is well managed, rich in humus may easily support 25 worms per cubic foot, which translates into at least 175 lbs of fertiliser per year for the same 200 sq. ft garden. This means that your garden or lawn can be supplied with far more fertiliser and that of superior quality than 10-20 lbs. of a dry or granular fast-acting chemical fertiliser. In fact, these chemical fertilisers may even repel the earthworms that are present because as the fertilisers become soluble, they leach down into the soil and force the earthworms to seek refuge elsewhere.
Worms can help change acid or alkaline soils toward a more neutral pH by adding calcium carbonate, a compound which helps balance the soils acidity (pH).
The tunnels that they make help to loosen the soil and this allows more oxygen in, and therefore aerates the soil, which not only helps the plant directly, but also improves conditions for certain beneficial soil bacteria. Finally, the tunnelling of the earthworms provide an access to deeper soil levels for the numerous smaller organisms that contribute to the health of the soil.
In summary, earthworm activity in your soil is beneficial and should be encouraged. They help incorporate organic matter, improve the soil structure, improve water movement through the soil, improve plant root growth and minimise thatch build up in lawns.
Needless to say, earthworms are beneficial.
How to increase your earthworm population
Now that you realise how beneficial earthworms can be, you may want to add to the population in your soil. This is easily done by adding plenty of organic matter to the soil. This does not need to be dug into the soil, just place it in a layer on the top, the worms will soon drag it down into the soil for you. Use home made compost, grass cuttings, dried leaves and even kitchen vegetable scraps (not meats or cooked foods though) as long as they are chopped up finely, or any other organic materials. They do the rest!
Are they a Friend or Foe?
The only time earthworms are a pest is when they leave small mounds or clumps of granular soil scattered about on the lawn. These are called "castings" and may be a nuisance when many castings accumulate. Sometimes they may enter drainage holes of containers sitting on the soil or sunken into the ground and the castings may clog the drainage holes as they accumulate in the container.
If you do have excessive worm mounds on your lawn, simply break them up with a rake or brush ( The traditional way is to use a besom or witches broom).
To prevent worms from entering containers, place a piece of fine mesh over the drainage hole. Setting the containers on a layer of gravel or cinders also keeps worms from entering, since they will not move through such a coarse layer.
Most of the time they are a friend to the gardener.
© copyright 1999, P. A. Owen
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