Building a wormery

Dr Delana Davies, Arable & Horticulture Technical Officer

A Focus Site project at The Fruit Farm, Llanvihangel Crucorney has taken up the challenge of building a wormery to process the fruit and vegetable waste from the 40 acre site. Vermicomposting is a faster method for reducing organic waste than traditional composting, and utilises the action of earthworms as well as bacteria to produce vermicompost, a highly effective fertiliser and soil conditioner.

A wormery needs to provide appropriate drainage and aeration, so container walls, bottom and side walls must be made of perforated material. An air space of at least 5-10cm depth below the floor of the wormery is essential for free drainage.

A wooden potato storage box approximately 1.2 x 1.8 x 0.8m high was lined with permeable polypropylene membrane and the bottom covered with a layer of sand and gravel topped with compost. 10kg of red wiggler worms were purchased and introduced together with their carrier medium and covered with about 10cm depth of shredded fruit and vegetable waste together with some shredded paper. The medium needs be kept moist, but it is generally unnecessary to add water as enough is normally provided by the raw materials added. Excess water will lead to waterlogging and a restricted supply of air, and worms need well ventilated conditions to live in. The box was then covered with a plank of wood to maintain shade and humidity.

Worms are most active in warm, moist conditions, ideally between 18 and 25ºC, and activity noticeably declines below 10ºC. It will now be a challenge to maintain the activity of the worm population through the winter, and some form of insulation will be provided between the membrane and the box wall. It will take a few months to harvest enough product to use as fertiliser for use at the site.

Separating the worms from the compost at harvest can be done by lifting the membrane sheet up by its four corners to make a mound in the middle. The worms will burrow to the bottom of the mound enabling the vermicast compost to be harvested off the top. The worms can then be replaced in the box to start the process over again.