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Harvesting worm castings and worms

Harvesting worm castings and worms is a largely manual process. Large-scale worm farming is a relatively new industry, and techniques and machinery are still being developed to mechanise the harvesting process.

Harvesting worm castings

Worm castings (or 'vermicasts') are the end products excreted by worms after they have eaten. Each worm can produce its own weight in castings every 24 hours. These odourless, slightly shiny pellets are rich in nutrients and can be used as a highly effective fertiliser.

Worm beds are usually ready for harvesting when most of the bedding has been depleted, leaving only the castings. Castings can be harvested in a number of ways.

Harvesting castings from raised worm beds

Raised beds are generally designed to allow castings to be collected from the base of the bed.

Harvesting castings from on-ground beds

One way to harvest castings from an on-ground bed is to move the pile of castings and worms to one side of the bed. In the space created on the other side of the bed, place fresh bedding and food. Gradually, the worms will migrate to the new bedding, allowing you to remove the pure castings that they leave behind. Once the castings are removed, you can refresh the bedding on the side the worms have left.

If you allow the migration to occur over about a month, you can be confident that any unborn worms in the pile of castings will have had time to hatch from their capsules and migrate across to the new bedding.

Another way to harvest castings from on-ground beds is to collect them at the same time as you harvest the worms from the bed. The following section explains how to harvest worms.

Harvesting worms

After a start-up period of 3 months, worms can be harvested at monthly intervals by carefully removing the top 10cm of bedding. You should then fork the worms and bedding/castings into mounds on a harvesting tray or table in a well-lit area. If you scrape the organic material away from the edges of the mounds, you will see that worms on the edges will burrow further into the mound to escape the light. Continue scraping the castings away until you have only small piles of worms left.

An easy method to harvest worms from open beds is to:

  • apply a fresh food source to the top of the bed
  • cover it to keep out the light
  • after 1 week, take off the cover and remove the top layer of the bed, which will contain the majority of the worms.

Some worms will still remain in the bottom material, but most will be harvested in the top layer.