How to make a good compost

Compost is decomposed vegetable matter and other organic material. Good compost is suitable for use in your garden soil as a way of returning nutrients to the soil, improving soil condition, providing humus, improving moisture retention properties and encouraging beneficial soil organisms.

Well decomposed compost will be brown, sweet-smelling and will break up easily. Don’t use it if it is green, slimy, bad-smelling or does not break up easily.

Where to Make Your Compost

You can compost by simply creating a pile in a corner of the garden. All you need is the space somewhere where water will drain well. The minimum size should be 1 m³ (1 m x 1 m x 1 m) for heat retention. However, a simple pile leaves much of the exterior of the pile (top and sides) exposed to the elements. In dry weather, the exterior will dry out and the micro-organisms that breakdown the organic matter will not thrive. In cold weather, the exterior will not have enough heat to keep the micro-organisms actively breaking down the organic matter. Exposed piles need to be turned and mixed regularly. It is best to have two such piles so that you can be adding material to one while the other is completing composting. If you have only one compost heap the most recent additions to the heap will not have composted fully while other parts are ready. You will need to leave it and stop adding until the composting has completed. Or you can carefully remove the completed compost.

The more you can enclose a pile, more of the whole pile will have good conditions for the micro-organisms that break the organic material down and you will get even decomposition.

There are many simple designs for compost bins and there are ready to use bins in hardware stores. Most cover at least three sides of the pile; three sides will reduce the exposure to elements by more than half. You can also cover the top, but be sure that some moisture and air is able to circulate into and around the top of the heap. Choose a bin design and size that suits your garden and the amount of vegetable matter you will compost from your kitchen and your garden.

Temperature of Your Compost

The temperature of the compost pile is an indication of the speed of the decomposition. The easy way to check the temperature inside the heap is by feeling it with your hand. If it is warm, decomposition is as it should be, but if it is the same temperature as the surrounding air activity has slowed down and you need to add more materials that are high in nitrogen to the bin; green material such as leaves or grass clippings.

Top Tips for Good Composting

• Find a suitable place to site your compost pile/s.
• Give your compost protection from the worst of the elements.
• Cover the compost with something that insulates the pile.
• Use non-diseased plant matter from the garden.
• Use weeds from the garden before they have produced seeds, but avoid roots of weeds that may re-sprout from root fragments.
• Shred heavy materials such as branches and twigs.
• Turn your pile regularly (every 1-2 weeks) to get oxygen into the pile.
• Move material from the outside to the inside and from the top to the bottom.
• Compost lawn clippings in several thin layers with other materials between the layers.
• Check the moisture of your compost pile; if it's dry add green stuff (e.g. leaves) if its wet and slimy add dry brown stuff (e.g. wood shavings, hay).
• Keep your pile insulated in cold weather.
• Chop stuff up if it is more than 10 cm.
• Check the moisture level of your compost; if it is dry add green stuff or wet it, if it is wet mix in dry brown stuff.

What You Should Compost:

• Kitchen vegetable scraps (add only small amounts of citrus fruit)
• Autumn leaves
• Lawn clippings
• Weeds (without seeds)
• The dung of herbivores (horses, rabbits, etc.)
• Wood ash (limit to a sprinkling)
• Wood shavings
• Shredded cardboard
• Seaweed
• Eggshells
• Tea leaves/bags
• Coffee grounds

Do Not:

• Site your compost in a place that puddles form regularly.
• Restrict access to the compost for turning.
• Cover your compost with polythene or other covers that would stop air and moisture.
• Use diseased plant matter from the garden.
• Use weeds that have seeded.
• Use large pieces of woody material in the heap; these take too long to break down (compost them separately).
• Leave your pile more than a month without turning; compaction will reduce air and cause slow anaerobic decomposition and bad smells.
• Just turn the surface layers.
• Add a thick layer of lawn clippings or autumn leaves.
• Let your pile get very wet or very dry; it should be moist and steamy in the middle.
• Let the compost get cold.
• Be concerned about earthworms and insects in the pile.

What You Should Not Compost:

• Cooked food
• Bread
• Pasta
• Meat
• Bones
• Large amounts of citrus
• Oils and fats (a little vegetable oil is OK)
• The dung of meat-eating animals (dogs, cats, etc.)
• Coal/charcoal ash
• Lime (mineral)
• Inorganic materials (plastics, metals, etc.)

Tips on Using Your Compost

• Don’t use your compost in the garden until it has been composting for at least 6 months. Compost that has not fully decomposed can take nitrogen from the soil and reduce the nutrients available to plants.
• Sift the compost through a coarse mesh screen or use your hands or fork to remove any larger lumps.
• Compost can be dug into the top layer of soil or can be added to the surface as a mulch that will continue to breakdown and release nutrients into the soil below.

Follow these tips and you will benefit from reducing waste and naturally improving the health of your garden soils!