Earthworms - Another Of The Gardener`s Friends
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.
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 come to the soil surface at night when temperatures are lower and humidity higher. 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. Many of us will at one time have heard that story, particularly children who may have a seen worm perhaps cut in half with a spade and watched as both ends continued to wriggle.
With over 2,700 kinds of earthworm they truly are an asset to the gardener, the only nuisance being to greenkeepers due to the mounds that worms leave on the surface of the grass which makes a playing surface less smooth.