Home-made compost is a brilliant money-saver. It recycles all of the vegie scraps, fallen leaves, lawn clippings and other kitchen and garden waste into “black gold” that is fantastic as a soil conditioner, mulch or simply providing organic material for our tough, West Australian soils.
Compost in the garden improves the physical, chemical and biological fertility of soil. It contains a range of nutrients that contribute to a plant’s growth but it’s the biological activity that has the greatest value, reducing the need for fertiliser, irrigation and sometimes even pesticides in the garden.
Good quality compost will improve soil structure and nutrient levels, increase the moisture content, reduce soil compaction and ultimately improve plant health and the harvest from vegie gardens. And, all this from the waste that the rubbish man would normally take away.
The idea behind any type of compost bin is simply that the waste material gently heats to anywhere up to 60°C which is ideal for the micro-organisms to begin breaking down the pieces to create humus. In bins that are open to the ground, earthworms will also move in, munching through the waste and creating air pockets behind them.
If a compost heap is located poorly or is not built with enough mass, the material will not reach the ideal temperature and composting will not begin. Of course, a bin located in full sun in the middle of summer could become too hot killing off the micro-organisms and drying out the mix.
The ideal site for a compost bin or heap is one that is reasonably sunny and except for fully enclosed bins such as the Aerobin, on bare soil. It is best not to put a compost bin directly onto a deck or paving as the liquid may damage or stain them. It is important that the compost bin is easily accessed from the house but at times it may become smelly so keep it away from the neighbour’s fence or your own outdoor entertaining areas.
A compost heap is probably the simplest of all techniques to build as it is simply a mass of about 1 cubic metre that is left for around six months to do its own work. The process can be dramatically quickened if the pile is mixed through with a pitchfork every four days to bring the material from the outer edges into the centre allowing them to reach a higher temperature and break down more quickly. Adding rotted animal manure or blood and bone will also speed up the process as long as the correct ratio of dry material remains. With some effort, a heap such as this may be ready in as little as 4 to 6 weeks
The next step up from the compost heap is a home-made compost bin made from left over materials such as fence posts, palings, lattice and even sheets of metal. These are used to build a four sided, bottomless box of about one cubic metre that sits on the ground into which the compost is piled making the area appear neater and the compost retained. Two bins sitting side by side are terrific as one full bin can be left to do its composting whilst the other is being gradually filled. These can also be turned occasionally and an old tarp over the top will keep out the vermin.
Plastic compost bins are incredibly popular and all work in a similar way. They have an open base and sit directly on the ground. They have the advantage of a tight fitting lid stopping the flies and pests from getting into the heap. They are inexpensive and suitable for even the smallest garden and of course, if more waste is available or compost needed, two or three bins can be used at the same time. A compost tumbler is a more expensive version except that it can be turned daily, resulting in compost much more quickly.
The Aerobin is a fairly recent innovation in home composting. It’s a very neat looking unit that is totally vermin and pet proof, requires no turning or maintenance and is insulated so that it continues to work all year round, even in shady areas. The sealed base allows it to sit on concrete areas that would normally be stained from open bins but the best thing is that to use the Aerobin, it is simply a case of opening the lid and dropping the material in. The material towards the bottom of the bin continues to break down so that even if it is not yet full and there is fresh material at the top, the hatch door at the base allows the compost to be accessed and spread onto the garden. The bonus is that the Aeorbin also creates a rich liquid fertiliser in a tank at the base which is easily collected from a small tap and watered around plants and vegies. For more information and a demonstration of the Aerobin, drop into any Better Pets and Gardens store.
FILLING THE COMPOST BIN
Practically anything that has lived can go into the compost but if everything is just piled into a heap it will fast decompose into a slushy, smelly mess. A little thought needs to go into building the compost mix so that the layers contain lots of holes and spaces allowing the oxygen to circulate. To do this, a third of the mix should always consist of dry, woody material such as sawdust, dry leaves, tree clippings, shredded newspaper, straw or aged green waste. These contain the carbon element and the green waste and vegie scraps provide the nitrogen.
Think of the compost heap or bin like a huge sandwich starting with a layer of straw or wet shredded newspaper and then alternating thin layers of kitchen and garden waste with layers of the dry, woody material. Add water as the pile is built to moisten the mix but don’t saturate it. Avoid compacting the pile since the bacteria and fungi need the oxygen available in the spaces to survive so that they can break down the material. Keep the pile or the bin covered to stop vermin and flies from getting to it and to help it reach the desired temperature.
Add a handful of garden lime to the compost to help break down the organic matter. Yarrow leaves and comfrey leaves are also useful for activating a compost heap.
If the mixture in the compost bin looks too dry, moisten it with water and increase the amount of vegie scraps and green foliage added to the heap. For mixes that are smelly and too wet, add sawdust or other dry material and turn the mix to aerate it.
WHAT TO ADD TO COMPOST
Vegie scraps and old fruit from the kitchen.
Crushed egg shells (but not egg products).
Grass clippings layered in between other waste.
Green and dead leaves from the garden.
Shredded newspaper or cardboard. Wet it first.
Mulched woody material from the garden.
Bedding from animals that are herbivorous.
Well rotted cow, sheep or chicken manure
WHAT TO AVOID IN COMPOST
Cooked kitchen scraps.
Cooked or raw meat (it will attract flies)
Dairy products such as milk or cheese.
Dog or cat faeces since they eat meat.
Roots from perennial grasses such as couch.
Plant material infected with pests or diseases.
Seed heads from weeds.
Citrus or onions, they are too slow.
Garden soil, it slows the process down.
HOW TO USE COMPOST
No matter what material goes into the heap, the resulting compost should be dark coloured, smell sweet and have a crumbly texture. Use gloves when handling compost and if it is dry, make sure to wear a face mask and hose the mix down before handling.
- Dig a generous amount of compost and well-rotted manure through the top 10 to 15cm of a vegie patch or garden bed several days before planting. The top surface is where the feeder roots of plants are so this ensures that they get maximum nutrients from the compost. It’s impossible to apply too much so be generous.
- Turn compost into liquid fertiliser. Add one part compost to three parts water and stir well. Let it sit for three or four days stirring every now and then. The liquid is useful as a gentle plant food though avoid pouring it over the leaves of edible plants. Strain it through an old stocking if applying it with a watering can.
- Compost is a brilliant addition to very dry soil that tends to become water repellant. The micro-organisms in the compost help to break down the waxy coating on the sand granules that cause the problem. Always apply it with a wetting agent for best results.
- Compost can be used as mulch but since it needs to be spread at least 4cm thick, most home gardens won’t be able to produce enough to cover all garden beds. Alternatively, use it as a thin layer underneath bought mulch.
- When planting, dig the hole to the same depth as the new plant but twice as wide. Mix lots of compost with the soil from the hole and use this to back fill. It will give the plant a great kick-start and improve the soil at the same time.
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