Earthworms and farmed worms
The best medium for growing healthy plants is a rich, loose, and fertile soil. Earthworms make a significant contribution by loosening the soil and providing plant nutrients in their droppings. When they burrow, worms aerate the soil to provide essential oxygen for bacteria, fungi, and other micro-organisms required for soil fertility.
An earthworm can digest approximately half its own bodyweight of soil each day. Given that average populations number hundreds of worms per square metre, the combined effect will be the processing and movement of large volumes of earth each year.
Earthworms concentrate essential nutrients and minerals from soil as it passes through their digestive tract. Their expelled waste, also known as cast, contains many times the nitrogen, phosphorus, and potassium that is normally available from soil. Additionally, these casts will contain higher concentrations of minor elements such as calcium, magnesium, and zinc. All of these nutrients and minerals are provided in a form that is readily available to plants, a fact that has led to their widely recognised status as a complete and effective plant food.
One way to encourage a supply of worm cast for the garden is to purchase live earthworms from an organic worm farm or garden centre. They are expensive so it is worth investigating to ensure the purchased species is compatible with the soil and conditions of their release location. To properly establish themselves in a garden, most varieties of earthworm require a loose, moist soil, one that also contains a reasonable supply of organic material. Another option is to raise a colony of Brandling (Eisenia foetida) worms at home. These are not earthworms but a separate species that normally breed amongst loose and decaying plant material. When raised properly in colonies, Brandling worms are efficient and capable of converting small quantities of organic waste into high nutrient cast.
Colonies of Brandling worms can be raised in manufactured worm bins or homes prepared from spare crates, boxes, aquarium tanks, or bathtubs. Any container used to house worms should provide a depth of at least thirty centimetres and have some drainage capacity at the bottom. When properly attended, worm colonies don’t smell and can be safely located in most sun sheltered spots with a reasonably stable temperature.
A new worm colony will require a minimum of one hundred worms to function properly. If more can be obtained, the colony can establish itself sooner and will be less likely to fail. Until they are making their own compost, a quantity of bedding material will be required to house and support the worms. Suitable materials include manure, compost, or leafmould. Fibrous material such as shredded paper, cardboard, or hessian can also be included.
It is beneficial to feed worms a varied diet of vegetable and garden scraps, including tea leaves, crushed eggshell, and dried fish bones. Overfeeding is a common mistake, particularly for newly housed worms in the process of establishing themselves. Brandling worms are very effective at breaking down organic matter but they are small organisms and their digestive systems can only process limited quantities at a time. If the worms are given more food than they can digest, the unused material will putrefy, making the compost acidic and foul smelling. When allowed to continue, such an environment becomes unsuitable for the worms and they will eventually die. Until their feeding capacity is properly understood, it is safer to restrict the supply of food each day.
After several months the worm farm will contain a supply of rich compost. A portion of this can be removed at any time by digging below the surface with a trowel. The compost can then be applied directly to garden beds and potted plants along with any liquid manure collected from the lower drain. Whenever worms need to be separated from their compost, the best approach is to spread the mixture thinly, outdoors on a sheet of plastic. A sheet of wet cardboard can then be folded over this as a canopy for the worms. Because they prefer to avoid heat, dryness and light, most of the worms will take refuge beneath the canopy and can then be collected as a wriggling mass.