How compost works in the soil
Compost returns some of the essential nutrients that feed our plants. It also provides food for earthworms and other beneficial organisms that help to keep soil healthy.
Compost improves the structure of the soil, helping to create tiny channels that allow air, water and roots to penetrate more easily.
In hard clay soils, compost loosens up tightly bound soil particles making the soil better draining and easier to dig.
In sandy soil, compost acts like a sponge soaking up moisture and nutrients that would otherwise be leached away and making them available for plant use.
With better soil structure, water penetration and water holding abilities, compost also improve the efficiency of water use in the garden.
Compost bins – what are the options?
You can make compost anywhere, anytime simply by collecting and piling up a load of organic materials on the ground. However, it’s a good idea to dedicate a permanent space in your garden to look after the day-to-day garden and household waste. It doesn’t need to be big - an area of about 1m x 2m is generally enough for the average household.
It’s not necessary to have a special composting bin, but it’s worth installing one to store the materials and keep the space looking tidy. Ready-made compost bins are a quick and easy way to get started. There is a huge selection available. Most are made from durable plastic and are simply installed directly on the ground. Consider installing at least two or three bins – that way you’ve always got one for adding ongoing waste and one or two with materials at various stages of decomposition.
It’s easy to make a tidy compost bin using bits and pieces found around the home like recycled timber posts, decking offcuts and corrugated iron. They look great and work beautifully.
The fundamentals of making compost
What can you put in compost? Add just about anything that was once living – animal manures, vegetable scraps, weeds, grass clippings, paper, cardboard and garden prunings.
Avoid adding the following:
Manures from meat-eating pets like cats and dogs – have the potential to pass on parasites and disease organisms to humans so are not safe.
Meat scraps – they break down slowly creating nasty smells and attract rats and mice.
Persistent weeds – many weed seeds won’t break down properly in the average compost system, so remove the seeds where possible, and avoid bulbous weeds such as oxalis, nutgrass and onion weed.
Diseased material – there’s a risk of spreading the problem to other parts of the garden.
Feed your compost a balanced diet – Aim for a balance of "green" and "brown" ingredients. The greens are fast breakdown items like grass clippings, manure, kitchen scraps and garden weeds. The browns are slower to break down, things like shredded newspaper, dried leaves, sawdust and other woody materials. Try to maintain a ratio of three parts green to one part brown.
Compost will get smelly when it’s anaerobic, wet and acidic – To fix the problem, add air to the heap by turning it with a garden fork, incorporate more brown materials to help dry it out and add some lime to restore the pH balance.
Microorganisms that break down organic matter need air and moisture – Keep the heap just moist and turn it regularly with a garden fork to aerate it. That way the materials will break down quickly.
How do you tell when compost is ready? – It should be crumbly with a rich dark brown colour and mild earthy odour. Most of the original materials will be unrecognisable, except for a few small chunks of woody material.
Worm farming
Compost worms are serious processors of organic waste, munching through 3 times their body weight in a week. The result is a nice pile of worm poo or worm castings, a beautiful rich soil conditioner. It’s easy to set up a worm farm at home and a good recycling option for people living in an apartment. Commercial home worm farming kits are readily available at garden centres, or you can make a simple worm farm at home using recycled materials.
Bokashi
Like worm farming, bokashi offers another good option for recycling kitchen wastes where space is limited. In the bokashi system, kitchen wastes are added to a small bin that can be stored in the kitchen. Each time the material is added, it is sprinkled with 'bokashi’, a dry material that has been processed and infused with 'effective microorganisms. These organisms ferment and preserve the material, stopping it from smelling and going rancid. The material doesn’t break down in the bin. The actual decomposition takes place when you add the materials to the soil, and when you do it releases lots of these beneficial soil-conditioning organisms. Plants love it!
