Composting is the accelerated natural breakdown of organic material by microorganisms. The resulting material can be used as an alternative to artificial fertilisers as it provides the full range of nutrients required for plant growth.
Compost can either be made in a pile or bin, depending on the amount of material for composting and the needs and size of your garden. A compost pile is useful for gardens with large quantities of greenwaste and a bin is often better suited to smaller suburban gardens. Compost bins can be purchased from your local hardware store or nursery, or you can make your own.
If compost is turned regularly, it should be ready for use in two to three months. By this time most of the ingredients have broken down into a balanced soil food.
How to make your own compost
- Choose a level spot in the backyard with some exposure to the sun, especially if you are using a smaller bin
- Always begin by using twigs or sticks at the bottom for proper aeration and drainage
- Then add kitchen scraps and garden waste to the top of the pile
- Keep the compost moist, and not soaking wet
- Turn it once a week if possible – this will speed up the process, ensure adequate aeration and reduce the likelihood of unpleasant smells
- After 3-12 months the compost will be ready to use. Dig it into new garden beds or spread it on top of established gardens
- The length of time it takes for the process to occur will differ depending on the material used for composting, the amount of air and water available and how often the compost is turned
- When your compost is finished it will have a fine, crumbly texture and a good earthy smell.
How to use compost
Your compost can be used in a variety of ways such as:
- An organic fertiliser for garden beds, providing all essential plant nutrients
- Surface mulch around shrubs and trees –the mulch should not touch the tree trunks
- A top dressing for the lawn – you may have to sieve the compost
- A potting mix for potted plants, using a ratio of 1:1 with garden soil
- To replace or improve lost and disturbed topsoil.
Green foods (nitrogen rich)
Aim to have about 25% of nitrogen rich (green) materials in your compost, including:
- Leaves (green prunings)
- Grass (green clippings)
- Cow, horse or chicken manure
- Fruit and veggie scraps
- Coffee grounds
- Tea bags
- Hair from your brush and comb
Brown foods (carbon rich)
Aim to have about 75% of carbon rich (brown) materials in your compost, including:
- Dried leaves and dried grass clippings
- Sawdust (not treated pine)
- Wood shavings (not treated pine)
- Hay and straw
- Vacuum cleaner dust
- Shredded paper
What not to compost
Some organic waste items may encourage vermin such as rats, flies and cockroaches, and will smell when they decompose. Some items to avoid include:
- Fats and oils
- Meat products
- Dairy products
- Bread and cake products
- Cat or dog excrement
- Man-made materials such as plastic, steel, aluminium and glass
Maintain your compost
Once established, you should use the popular A.D.A.M principle of composting:
- A is for aliveness – when there are micro-organisms, bugs and worms living in your compost, it is working well.
- D is for diet or diversity – make sure there is a range of different materials in the compost, and in the right proportions i.e. 25% green, 75% brown.
- A is for air – turn your compost every week so there is plenty of air moving around. This reduces bad smells and helps the material break down faster.
- M is for moisture – damp but not wet compost works best.
Compost problems and solutions
Listed are some problems that may occur, the cause and some useful solutions.
|Problem||Cause and solutions|
Material is too wet:
Not enough air:
Slow composting process
Too much woody material:
Material is too dry:
Brown segmented larvae
Not enough air:
Small vinegar flies
Pile is too acidic
Addition of fruit over time:
Easy access to food scraps:
Mice nesting in pile: