Compost is formed in nature all the time as plants and animals die and decompose. This natural compost is generally called humus. Decomposition involves the breakdown of plant and animal remains into simpler components. As a result nutrients, which are essential for plant growth, are released into the soil. Decomposition is brought about by the action of decomposers which include bacteria, fungi, and earthworms. The process of decomposition is essential for the recycling of nutrients.

By making compost in our gardens we imitate nature and ensure that our gardens are healthy and productive. Compost returns nutrients to the soil, increases the soil's ability to hold water and air, and prevents erosion by binding the soil.

About half of the refuse we throw away each day can be turned into compost, thus reducing waste, recycling valuable resources and enriching the soil. Composting is a cheap and hygienic way of converting waste into a clean-smelling substance that will improve the soil and make any garden flourish.

WHAT TO USE IN MAKING COMPOST

Most organic (of plant or animal origin) materials that will rot or decay easily are suitable for composting.

Garden wastes: grass cuttings, non-woody garden prunings, leaves, flowers, and vegetable remains.

Kitchen wastes: vegetable peelings and leaves, fruit peelings and cores, cooked table scraps, tea leaves and bags, egg shells, stale bread.

General: paper and cardboard, sawdust and woodshavings, animal manure, woodfire ash, seaweed.

Materials which you should not add to a compost heap: kikuyu grass, woody garden clippings, pine needles, rose cuttings and other cuttings with thorns, seeds, bulbs, runners, garden wastes sprayed with pesticides, toilet waste or septic tank sludge, diseased animal carcasses and diseased plants, anything that does not decompose, e.g. metals, glass, plastics.

BUILDING A COMPOST HEAP

Remember that compost can be made in many different ways, and these are only general guidelines. In fact, nature does it without any help from people!

A good size for the compost heap or trench dug into the ground is 2 m by 2 m, depending on the amount of compost you want to make.

* Mix the organic material well and chop up any big pieces - do not add layers of only one material, such as grass cuttings or leaves to the compost heap.

* Start by putting down about 200 mm of mixed organic material.

* If you would like to speed up the process of decomposition, add a "starter". This might be a bucketful of mature compost, animal manure, or bone meal. Commercial starters are available at nurseries and garden shops.

* You can also add soil to the growing heap as the many organisms that it contains will multiply and help the rotting process. Earthworms in particular are valuable members of the compost heap community. They eat plant material and produce worm castes that are very rich in nutrients. They also help to mix the compost ingredients and put air into the heap thereby speeding up the process of decay.

* Continue building the heap in layers of about 200 mm. The last layer should be soil, dry grass, leaves, or sawdust, as this will keep smells in and not attract flies.

TURNING THE HEAP

After one week push your hand into the compost and you will feel the heat generated by the decomposition process. After a few weeks the heap will have cooled down and this means that it should be turned and allowed to heat up again. The heat kills the weed seeds and fly larvae.

Turning encourages decomposition and speeds up the formation of compost. The time between `turnings' of the heap depends on the speed at which decomposition takes place, and this in turn depends on the ingredients in the heap, and the weather.

WATERING THE HEAP

Keep the heap moist, but not water-logged as this inhibits decomposition and will make the compost smell. If it does get too wet, add absorbent material such as sawdust, straw, or manure, and turn the heap.

CONTROLLING PESTS

If your compost heap is cared for correctly, flies, rats and mice will not create a problem in the garden. Flies can be controlled in a compost heap by immediately covering new material with dry soil, sawdust, grass or leaves. As flies breed in compost, the heap should be turned frequently so that enough heat is generated to destroy fly eggs and pupae. If you do find large white worms in the compost, destroy them. They are the larvae of the large black and yellow fruit beetle which does much damage in the garden.

Do not add meat scraps to the compost as this will attract rats and mice. Do not use any poisons such as insecticides to control pests as these will stop the decomposition process by killing the organisms responsible for decomposition, e.g. fungi, earthworms, bacteria.

USING COMPOST IN YOUR GARDEN

Compost is mature and ready to use when it looks crumbly and has an earthy smell. It can then be dug into the top-soil of garden beds or spread as a mulch under trees and bushes. Compost also makes a very good potting mix for houseplants or seedling trays.

FURTHER READING

HANDS ON: SOIL AND COMPOST LIFE - A FIELD GUIDE. I. van den Berg. Share-Net, PO Box 394, Howick, Natal, 3290. Tel. 0332-305721.

SOIL IS LIFE: A HANDBOOK FOR TEACHERS. M. Roos (ed). Share-Net, PO Box 394, Howick, Natal, 3290. Tel. 0332-305721.

Enviro Facts: Soil, Soil Erosion.

USEFUL CONTACTS

Green Industries Council. PO Box 3554, Halfway House, 1685. Tel. 011-3151920. Branches countrywide. Promote gardening for the improvement of home and environment.

Food Gardens Foundation. PO Box 41250, Craighall, Johannesburg, 2024. Tel. 011-880 5956/7.

Abalimi Bezekhaya. 37a Somerset Road, Cape Town, 8001. Tel. 021-252095. Food gardening and greening project.