Kitchen scraps and garden waste are great garden improvers

By: David Walker, October 19, 2009

I recently came across an interesting on-line publication called G Magazine. It is an Australian consumer sustainability magazine, published in Sydney since November 2006. See http://www.gmagazine.com.au/ for lots of interesting tips. A recent posting by Liza Ellis gives some great information on composting.

Liza tells us that Australians toss a staggering half-tonne of organic matter per person into landfill each year, only for it to sit around in the oxygen-starved environment where it doesn't decompose as it otherwise would.

Composting not only keeps organic matter out of landfill, but it's also great for creating a nutrient-rich, less thirsty soil.

Compost is, essentially, the decomposed remains of organic matter. It is excellent at improving all types of soil by acting as a natural fertiliser and helping to reduce soil disease. Drainage in clay soils and water retention in sandy soils can be dramatically improved with the addition of compost.

Creating a mound of great compost is not quite as simple as tossing the scraps on a pile. To get the most out of your compost, you should avoid adding certain types of scraps and make sure the heap is appropriately contained with a good amount of water and aeration.

The simplest composting is in an open heap. It may be messy; it's a good way to compost lots of organic matter and makes turning and aerating the pile much easier.

The square, plastic and DIY assemble kits are another option and easy to use. If you go for the bin option, make sure it's accessible. For an outside space, position the bin on the soil and in the shade - ideally under a tree or in an easterly position - to prevent the workaholic earthworms from dying.

Suitable compost ingredients include food scraps, tea leaves and tea bags, coffee grounds, newspaper, other paper and cardboard, leaves, lawn clippings and prunings, and crushed eggshells. Small amounts of onion and citrus peels are not problematic.

Avoid adding fats and meat as these may attract vermin and become flyblown. 

Create thin layers of any one ingredient - newspapers and lawn clippings are useful for separating layers.

Work towards an even carbon-to-nitrogen ratio of ingredients, making sure to include an equivalent amount of nitrogen-laden kitchen scraps and lawn clippings to carbon-rich newspaper, dry leaves, sawdust and hay.

Smaller scraps compost faster, so cut up kitchen scraps, mow over leaves, shred newspapers and mulch garden prunings before tossing them onto the pile.

Keep compost moist but not wet - too much moisture deprives the heap of air, causing it to smell. Conversely, too little water slows the composting process down. A telltale sign of this is the presence of ants, so add water if they're around.

When you start your compost bin turn the contents once a week to increase aeration and composting activity. Air vents on side panels of bins are often inadequate. Insert a rake handle in the heap to create airholes.

Composting takes about 8-12 weeks to break down matter into the familiar-looking crumbly brown humus. At this stage it smells sweet and can be added directly to garden soil.

Fork it through the soil around the root zones of your favourite plants.

Healthy compost does not smell unpleasant and should be about as wet as a damp sponge. If it's too wet, add dry organic matter. 

Continue to aerate the heap, and add some garden lime or gypsum.

Other compost accelerators include blood and bone, chook and other manure, seaweed emulsions such as Seasol and fish fertilisers like Powerfeed or Charlie Carp.

When emptying the compost bin, ensure that you keep some compost aside to mix into the next compost heap so micro-organisms can get to work immediately.