Have you ever thought about what actually happens when things rot? It may be that, like me, you have got confused reading garden books, as they are usually full of vague meanings for words like `stabilised humus'!

Many of you may think that making compost is an unpleasant or difficult processwell, I can assure you, it's not!

For a fast track way of changing crude organic materials into humus (something resembling soil) read `a compost pile'. The word humus, however, is quite often misunderstood, together with the words organic matter and compost

Making compost is really a very simple process. It can become a natural part of your yard or gardening maintenance if done properly. If you are mowing your lawn or weeding your flower-beds, making compost doesn't have to take any more effort than bagging up your garden waste.

To me, astounding as it may sound, handling well-made compost is actually a very pleasant experience. Don't but put off by compost's `dirty, nasty' origins. There is little similarity between the healthy-smelling black or brown, crumbly substance dug out of a compost pile and the garbage, leaves, manure, grass clippings and other waste products from which it began.

To define composting precisely, it means 'enhancing the consumption of crude organic matter by a complex ecology of biological decomposition organisms.' Many raw organic materials are eaten and re-eaten by thousands of tiny organisms from the smallest (bacteria) to the largest (earthworms).

The components are altered gradually and recombined. Unfortunately, many gardeners use the terms compost, organic matter, and humus as interchangeable identities. However, there are important differences in meaning that need to be explained.

This organic matter food gardeners are vitally concerned with is actually formed by growing plants that manufacture the substances of life. Most organic molecules are very large and complexinorganic materials are much simpler. Of course, animals can break down, reassemble and destroy organic matter but the one thing they cannot do is create it.

Only plants can make organic materials like proteins, cellulose, and sugars and they produce this from inorganic minerals derived from air, water or soil. The elements plants use to build include magnesium, calcium, phosphorus, potassium, sulphur, sodium, cobalt, zine, iron boron, molybdenum, carbon, manganese, nitrogen, hydrogen and oxygen

Thus, it is organic matter from both land and sea plants that fuels the entire chain of life from worms to whales. Because humans are most familiar with large animals, they rarely stop to consider that the soil is also filled with animal life consuming organic matter or each other.

Our rich earth is crowded with single cell organisms like bacteria, fungi, actinomycetes, rotifers and protozoa. Soil life forms increase in complexity to microscopic round worms called nematodes, various kinds of molluscs like slugs and snails (some so tiny the gardener has no idea they are even there), thousands of often microscopic soil-dwelling members of the spider family (arthropods), insects and, of course, the larger soil animals most of us are more familiar with such as moles.

The entire sum of all this organic matterliving plants, decomposing plant materials, and all the animals, living or dead, large and smallis sometimes called biomass. One realistic way to gauge the fertility of any particular soil body is to weigh the amount of biomass it sustains.