Scientific Name: Lumbricus terrestris
Earthworms feed on partly decomposed organic matter in and on the soil, this is broken down further and after excretion the 'castings' are acted on by the soil micro-organisms. This means that the earthworm is an important part of the recycling of nutrients in the soil. Charles Darwin studied them closely and recognised their role saying, "It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.". In addition their burrowing aerates the soil and improves drainage, helping other soil organisms and plant roots.
The worm casts contain higher levels of nitrogen, phosphorous and potassium than the surrounding soil - the products of digested organic matter and trace elements brought up from deeper levels. Calcium carbonate is also added and this can make acid or alkaline soils more neutral. This 'fertilizer' is distributed throughout the soil and research has shown that each worm can produce about 150g per year - much better than a dry or granular fast-acting chemical fertilizer which has no humus, leaches away and may repel the worms. Some gardeners collect worm casts to use as a fertilizer and soil conditioner.
Earthworms usually dwell in the top few centimetres of the soil, but some species will go down nearly 2m. They need moisture to breath, and burrow deeper if the soil dries out or freezes. However, they will drown in waterlogged soil so the increasing periods of prolonged wet conditions may harm the population - they are forced to the surface and birds exploit these conditions to make easy pickings of them. They come to the soil surface at night when temperatures are lower and the humidity is higher; also the birds are not about. Most soil types are suitable except very acidic, and coarse sand.
They can reproduce when 3 - 6 weeks old, making a cocoon in the soil from which live worms emerge. The common view that cutting a worm in half makes two is not true, they can regenerate body parts in some cases, but usually both parts die.
Unfortunately the worm population of Northern Ireland and Co Down in particular, is under great threat at present from the New Zealand Flatworm. This interloper feeds exclusively on earthworms and can reduce the numbers to below detectable levels in the right conditions.
To increase the worm population, adding organic matter provides food and adding lime to acidic soil will help. They are said to like mint and planting it is supposed to attract them to the area. The Brandling worms (Eisenia fetida) sold as fish bait are not suitable as they need the warmth of the wormery or compost heap.
Some people, notably greenkeepers, do not welcome the worms because of their 'casts' which spoil the perfect playing surface they are trying to achieve. A top-dressing of coarse sand has been shown to reduce the production of casts - I suppose they don't like eating sand or abrading their skin on it, any more than we do! An application of about 4cm split over three to four months should have some effect, ie. six or seven x 0.5cm every two weeks.
Earthworms are very important when recycling organic waste. They populate every compost heap and special wormeries or composting toilets mean we can keep all of the humus and nutrients for use at home. (Though you might have to watch out for animal welfare groups, recently in New Zealand a special study had to be carried out to see if the worms are traumatized by the ordeal, fortunately it was found that they are not.)
To find out how to set up your own wormery for composting kitchen waste check out this video:-Back to GARDEN CREATURES
