Starting a worm "compost factory"

YOU can set up your own earthworm colony to produce vermicompost and at the same time cut down on your garbage. Graeme Eggins compiled these notes based on information in the CSIRO Division of Soils handbook Earthworms for Gardeners and Fishermen.

Containers

Match container size to the size of your proposed operation. The smallest practical containers are foam fruit & veg boxes. Alternatively make your own, about 30cm deep, of wood (don't use metal). If your main purpose is to dispose of kitchen scraps, allow about 0.15 sq m of surface per person in the household. For larger operations build raised beds about Im wide and 30cm deep, directly on the soil or on concrete (easier to remove the vermicompost). Add drain holes if the base is concrete and the beds are open to rain.

Site

A small earthworm culture bed should not smell unpleasant. It can be sited anywhere where it is sheltered from direct sun, from frosts and preferably from rain. Use shade cloth if natural shade is not available.

Type of earthworm

To produce vermicompost you need worms capable of growing fast and breeding prolifically in a rich organic environment. In Southern Australia that means you choose tiger worms (Eisenia ferida). They would be worth trying on the North Coast. Under ideal conditions, eight tigers can increase to 1,500 in six months. You can also use Lumbricus rubellus, but it doesn't work as quickly as Eisenia fetida .Alternatively you can try a variety common in your district. Ask around and you may well find someone willing to sell you compost worms.

Bedding materials

You normally start a worm culture by providing a porous bedding material such as cow or horse manure. If you can't get manure use peatmoss, shredded paper, a mix of straw and grass clippings, leaf mould or a mixture of the lot. Bedding must be moistened until it is just possible to squeeze a few drops from a handful. The bed can be a little wetter in summer but should be drier in winter. However, many of the species found in garden and field soils don't like such a rich organic mixture. For them, start with a 5cm layer of loamy soil, then IOcm of immature compost, leaf mould or well rotted animal manure and finally another 5cm of soil.

Adding the worms

Add about 50 worms to each litre of bedding. This works out at about 500 per foam box or 2000/sq m of larger beds. In boxes, the worms should be added at one spot along with a supply of food. In larger beds scatter worms along the full length, after burying food below the surface. Any worms that don't quickly dive underground should be removed. The beds should then be covered with hessian or weed mat to exclude light and reduce evaporation. Black plastic can be used but it must be loose enough to allow air into the beds.

Food

Almost any dead organic matter can be used as food as long as it contains at least 1% nitrogen. That means you can use almost everything except sawdust, twigs, bark, paper, cardboard and gum leaves. (You can use these other materials if they are accompanied by materials with higher N contents.) Manures from grass-fed animals and partly composted garden wastes make excellent worm food provided they are cool, not hot when applied.

Lawn clippings, leaves and other bulk materials are usually scattered on the surface of the bed. Kitchen scraps are best chopped into smaller pieces and buried at various spots. But don't give more food that the worms can process.

Keep adding food to the bed until there is sufficient vermicompost to harvest. Then cut off the food supply, thus forcing the worms to work over the bed materials until most of it is pure castings. Usually, as the worms run short of food their rate of growth and breeding will slow down. A small amount of grit in the bed helps the worms grind food in their gizzards. Most manures and garden weeds contain some.

Management

Don't give the worms more food than they can eat. As a guide, 2kg of worms need about Ikg of kitchen scraps or equivalent a day. Keep the bed just moist enough so that you can just squeeze a few drops of water from a handful of material.

Beds under cover need sprinkling every two to seven days, depending on the time of year; Outdoor beds must have good drainage. Maintain aeration by loosening the bed every couple of weeks with a fork. Try not to disturb the worms more than absolutely necessary. Also try to keep the temperature of the bed between 12 degrees C and 25 degrees C and the pH in the range 6-8. A pleasant earthy odour is a sign of a well managed worm bed.

Harvesting

Worms normally take about six months to produce quality vermicompost. The simplest harvesting method is to pile the contents of the bed into a heap on a solid surface in a brightly lit area. The worms will move down away from the light, allowing you to repeatedly remove the lop layers. Alternatively some kind of screen can be rigged but it is usually wise to encourage as many of the worms as possible to get out of the way first.

Readers' Comments

Lots of wormfarming information and questions answered at wormfarm.com

Contributed by Betty Eieley ettybays@juno.com on January 16, 2001

From: 78er@tpg.com.au
Date: Tue, 4 May 2004

my experiences so far

ants can be controlled using lime or spot wetting
cockroaches can be controlled using crushed eggs shells
rats fine wire mesh added to the base
tree roots move it around when full
been so successful I now have to buy waste

peter

From: Niki.Lee@environment.gov.au
Date: Mon, 30 April 2007

We have a problem with cockroaches in our worm farms too. This is despite them being in a temperature controlled laboratory with daily maintenance and a strict diet.

My advice is to manage the cockroaches when first detected this way you can dispose of them manually, and prevent the cockroaches spreading by keeping the legs of the elevated type of farm/container in water. Otherwise it is too late! I am about to experiement with raising the pH with lime, then I might try the egg shells as suggested but I wish I had gotten rid of the few I saw in the first place.

niki

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