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A beginner’s guide to composting

Why composting?

When we send compostable material such as kitchen scraps to landfills, it produces methane as it breaks down. One study showed the decay of a family’s food and garden waste that is not composted aerobically generates almost one tonne of greenhouse gas each year.
Adding organic matter to our soils can literally turn them into a sponge, dramatically increasing water holding capacity. If you want to grow tender plants like vegies in our hot, dry, Mediterranean-like climate, improving your soil is essential.

Adding compost also feeds the living soil biota. Microscopic microbes are really important to soil health and plant growth. If you are new to composting, this article is for you. Here, Sophie Thomson – ACH Group’s contributor will provide some helpful tips on how to make your own compost.

Getting started: how to make your own compost

Most compost systems work aerobically, meaning that oxygen is involved. These include open bottom bins, tumblers, Aerobins or three bay systems with wooden, tin or even hay bale sides. 

Once you have a compost set up, the trick is to make the right mix of ingredients. You need to have the right balance of carbon (brown) and nitrogen (green). Carbon comes from brown, dead or dry ingredients and includes woody plant matter such as straw or hay, dried grass clippings, dry leaves, shredded paper and newspaper (non-glossy) and even dog and human hair.

Nitrogen is from green, wet or fresh materials and includes living plant matter such as green lawn clippings, weeds without seeds, fresh prunings, food scraps, fresh horse or cow manure, tea bags and coffee grounds, even finely crushed eggshells.

The idea is to add layers of brown and green, keeping a balanced mix which will create enough heat to start the breakdown process. As a rough guide, you will need two to three buckets of brown dry material for each bucket of green.

It is best that you chop the ingredients using a mulcher, by popping fresh prunings on the lawn and running over them with a mower, or even by hand with a pair of secateurs kept by the compost area. Thick or hard fleshy stems like the stalks of cabbages and cauliflowers can even be broken up by smashing them with a hammer.

Compost needs air, water and heat. Air is added each time you turn a compost pile, or pull out plugs from your pile to open it up with a compost screw. Water needs to be monitored; add moisture when it is hot and cover with something waterproof if it is getting too wet.

If your bin is too dry and takes too long to break down, you need more fresh material or water; if it is wet and smelly, you have the opposite problem. You can always pull the pile apart and start again, getting the layers and mix right.

Worm farms and Bokashi buckets

For households where you mainly produce kitchen scraps, you might also like to consider a worm farm or a Bokashi bucket. Worm farms can be bought or made from old bathtubs, concrete laundry sinks, or old fridges and freezers. They can be fed kitchen food scraps, but you must leave out onions, citrus, dairy and milk. The solid matter produced by worm farms is known as worm castings or vermi-compost and can also be applied as a soil improver.

Bokashi buckets are usually kept inside in the kitchen or laundry and don’t smell. They take kitchen scraps including onions, citrus dairy and even fish bones. This is an anaerobic process which works by fermenting the food scraps while keeping the goodness in the food. When the bin is full you simply bury the contents in the soil, where the oxygen in the soil makes it break down rapidly and turn into compost.

Both worm farms and Bokashi buckets produce a liquid leachate which is best drained off weekly, and used in a watering can, diluted to the colour of weak tea. This liquid is full of microbes and can be used as a soluble plant food and soil stimulant.

If you are lucky enough to have chooks, they can also be part of a composting system as you feed them all your kitchen scraps and they then value add, producing manure and eggs. A win-win situation!

Leaf mould for composting

For gardeners who have large volumes of fallen leaves, make a bay around 1m square using four star-droppers edged with corrugated iron, or chicken wire lined with cardboard. Pile in your leaves. Speed up their breakdown by sprinkling pelletised chicken manure through the heap, shredding large leaves with a lawnmower, and turning the pile occasionally. Leaf mould is a valuable source of organic matter to improve the water-holding capacity of your soil. 

For more information visit abc.net.au/gardening/ or the Sustainable Gardening Australia website www.sgaonline.org.au. Check out another blog by Sophie Thomson on 10 veggies to grow in small spaces.