Worm farms

Page last updated: Wednesday, 12 March 2014 - 2:05pm

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As a rough guide, 1 kg of worms (3000 to 5000 individuals) need 3 to 4 kg of food per week. Do not over-feed the worms. You will know when you are if the food is constantly uneaten and the mix ‘sours’ or seems too soggy, it may also start to smell rancid. A good bed should be damp, not wet, and should smell nice and earthy. A freshly fed bed has a lumpy irregular surface. When the lumps disappear and the surface becomes smooth, this confirms the worms are eating the food and are ready for more. As the worm population grows they will start eating more food. Worms don’t have teeth and can feed more easily if the scraps are finely chopped. Digging their food under slightly with a small garden fork makes it more accessible to them also, because worms detest the light.

Keep the pH of the bedding about neutral (pH 7). If it is too acid (pH 5 or less), light sprinklings of lime or dolomite will help to neutralise it. Worms are often pale-coloured in acid beds. Unsuitable alkalinity (pH 9 or more) may be corrected by adding coco peat and shredded newspaper. pH testing kits are sold at garden centres.

Check the texture of the contents in the top tray (bedding) from time to time.

The ideal bedding should be:

  • Able to retain moisture
  • Well drained
  • Neutral pH (6-8)
  • Light and crumbly

Food scraps will generally keep the system moistened, but you need to check for dryness at least once a week, especially in warmer months. If the bedding seems too dry add water. A handful of bedding, squeezed with a strong hand, should produce a drop or two of moisture. Don’t over water the system because excess water will displace the oxygen in the bed and worms need plenty of oxygen. If the worm farm bedding does become sludgy, mix in some handfuls of straw or strips of newspaper. It is also a good idea to aerate and turn the bedding carefully, about every two weeks with a light fork. Contrary to folklore, worms do not usually survive being cut in half with a shovel.

Under ideal conditions, the numbers of some worm species can reach 5000 individuals in only the space of a large bucket, and they may double their collective weight each month if they have enough space.

When the worms reach large numbers or the tray is full with worm-casts, stop adding food. After two weeks of non-feeding, swap the trays so the feeding tray with the worms is now the middle tray. Collect the previous middle trays’ contents for use in the garden. Refill this tray with new bedding (to attract the worms) and place on top.

Again, make sure the top tray sits firmly on the surface of the bedding in the middle tray so the worms can migrate upwards freely. If using a non-stacking or a homemade tub-styled worm farm you can dry the bedding off by not watering, forcing the worms down to the moister mix below. The castings on top can then be skimmed off for use in the garden. New bedding should then be added and carefully turned through with a fork.