Vermicompost (or worm compost) is produced by feeding kitchen scraps and shredded newspaper to worms. The worm often to be found in the compost heap is in fact a different species from the common earthworm found in the soil. This is Eisenia fetida or the Brandling worm, also known as the Tiger worm or Red Wriggler. These may arrive naturally, or can be introduced–they are available from mail-order suppliers, or from angling shops where they are sold as bait.
Above: Diagram of a household-scale worm composting bin
Worm composting can be practised on a small scale in a special bin, a very suitable system for turning kitchen wastes into fertility where space is limited. When beginning a bin, as many worms as available should be added to bedding created from shredded newspaper and potting compost. Once established, small quantities (not more than the worms can cope with before putrefying) of kitchen waste can be added to the bin daily. Care should also be taken to maintain optimum moisture levels (excess liquid can be drained via a tap and used as a plant food) and pH (adding an occasional handful of lime, will prevent excess acidity). Worm compost is too rich for use as a seed compost, but is useful as a top dressing, or as an addition to potting composts.
Vermicompost has a triple action on the soil:
- It improves the physical structure of the soil.
- It improves the biological properties of the soil (enrichment of micro-organisms, addition of growth hormones such as auxins and gibrellic acid, and addition of enzymes, such as phosphates, cellulase, etc.).
- It attracts deep-burrowing earthworms already present in the soil.