Compost worm farms

compworms.jpg For organic gardeners who don’t have enough recyclable waste for a productive compost heap, a compost worm farm is the answer.

Compost worms are different from earthworms that tunnel through soil and move into compost heaps after organic matter has been partly processed by microorganisms. Consequently, the term ‘compost worms’ can be confusing to new gardeners. Worm farm (compost) worms require a moister and cooler environment than earthworms (10–30° C.), and feed on a wide range of organic matter, including vegetable and fruit waste (except for citrus and onions), wet paper and cardboard, grass clippings, aged cow and horse manure, soft weeds and hair. Chopping waste into small pieces provides a larger surface area for worms to feed on and speeds up production. The digested waste (worm castings) are a clay-like humus that contains all the nutrients and trace elements that plants need for good health in a form that plant roots can absorb immediately.

Worm castings are Nature’s slow-release, complete organic fertiliser. The more varied the worms’ diet, the better the fertiliser. Simply rake the worm castings into the topsoil on garden beds. As they do not smell, they are the perfect fertiliser for both indoor and outdoor pot plants. They are also a great addition to seedling mixes and, when diluted to very weak black tea strength, the liquid that drains from the worm farm is a fertiliser that gets seedlings off to a flying start.
Worm farming has become a very popular method of recycling and various commercial worm farms are available to suit different situations. Most children find worm farms fascinating and enjoy looking after them.

  • Commercial worm farms come with complete instructions, a starter colony of worms and edible bedding for the worms. Small commercial farms with several tiers are easily moved into a shed or garage in areas where frosts occur. Or, in frost-free areas, if you can find an old hip bath or large sink, you can make your own worm farm as we have here. Worm farming
  • Containers with a drainage hole prevent moisture build up in the base of the farm and a waterproof cover excludes light and rain. (Avoid using old carpet or underlay as a cover as these are impregnated with pesticides.)
  • Add a little water to the farm when necessary to keep the food and bedding damp.
  • A light dusting of dolomite every few weeks will keep the worm farm smelling sweet and the pH close to perfect.

Worms in farms with stacked trays will move up into the next highest layer when all the food in their tray has been eaten, and it is time to collect the worm castings.
Uncover the worm farm and leave the surface exposed for 15-20 minutes. The worms will move down through the castings away from the light. The castings will contain worm eggs. These are easily recognised as you can see in the photo. They are about the size of the head of a match, or a little bit smaller. Worms don’t lay their eggs in groups like some insects do. They lay them one at a time through the worm castings, but usually close to where they can find food when they hatch.
Harvestcastings1 Use a scoop to collect a layer of castings from the top of the farm. A scoop can be made from a 2 litre juice bottle with a handle. Spread the castings onto an old tray by lightly brushing the castings with gloved hands. Check for worm eggs and any small worms that might still be in the castings and put them safely back into the farm. Cover them with a layer of food.
Then tip the collected worm castings into a bucket and collect another scoop full of castings until you have enough to put into your garden bed, or to make ‘worm tea’.

Worm farming

compworms.jpg My husband has been busy with his chain saw carpentry again. He rescued a shower base bathtub from the local tip to make a small worm farm that could be set up in a shady spot near the house. This makes it easier for me to collect worm castings for my seedlings and pot plants. Worm farms are a wonderful way to recycle food scraps and household waste into fabulous 100 % organic complete fertiliser with a neutral pH.
Old bathtubs are hard to come by in our area, as they are popular for recycling as water troughs for horses. However, this tub was missing the plug rim and unsuitable for use as a water trough, so it was a lucky find.
Using his trusty chain saw, Brian built a simple frame for the tub, using scrap hard wood pieces from around the farm. The cover consists of recycled hardwood planks, placed side by side, across the top of the farm. Only the two end planks are attached to the frame. The loose planks allow me to expose as much, or as little, of the worm farm surface as I want when adding food or collecting castings. A large square of fly screen was placed across the base of the tub before filling to prevent the worms and castings falling through the drainage hole. A bucket is positioned under the drainage hole of the tub to catch the liquid that drains from the worm farm.

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A layer of edible bedding is needed across the bottom of the farm container for to keep the worms damp and protect them from temperature fluctuations. I added some of the digested matter from our main worm farm for bedding as this contained both worms and worm eggs to ensure that numbers in the new worm farm will build up more quickly. However, for new worm farmers, bedding can be shredded and soaked coconut husk fibre (Coco peat), or damp, aged cow or horse manure, and the starter worms are placed over the bedding where you want them to feed. I added some chopped scraps (in a 2-cm layer) to one half of the surface of the farm, so that the worms would be concentrated in that area. The surface of the farm was then covered with wet newspaper and the cover planks over the top of the farm. (A temporary plastic cover goes on when heavy rain is predicted.) Food is replaced as often as necessary. If your worm farm is new, don’t give them too much food at first or it will be a while before they eat all the food, and it will start to smell. But, if you don’t give your worms enough to eat, their growth and reproduction will be slow.

As worm numbers increase, they will be able to process larger quantities of waste. Once the worms have turned the food and bedding in their area into castings, I start putting food at the other end of the farm. This allows me to collect castings more easily from the other half and pour water through the processed bedding to collect some liquid for my plants. It is not recommended to pour water through undigested food in worm farms in case the food has been affected by fungal or bacterial disease. However, using common sense and following the organic principle of “feed the soil, not the plant”, avoids problems with liquid fertilisers.