BUILDING A COMPOST HEAP BY LAYERS

Organic growers consider their first duty is to nurture the soil in which they grow their produce and to do so without the use of artiificial fertilisers, herbicides or insecticides. Organic growers believe in using natural fertilisers and letting nature work for them. This article is about compost, which many assert is NATURE'S SUPREME FERTILISER. A small amount of compost will go a long way in promoting the biological activity that is so essential in organic growing.

Many people think that compost is the result of throwing kitchen scraps and garden refuse in a pile and letting it rot. This is not exactly the case.

Good compost is composed of many different ingredients. Perhaps the most important is some sort of manure, cow, horse or poultry. Other ingredients include grass clippings, leaves, weeds, sawdust, wood shavings, kitchen scraps. seaweed, straw and hay. The addition of rock phosphate or dolomite will enrich the finished compost. And, of course, water is an essential ingredient. If the heap is not moist enough it will not work. Nine times out of ten, when a compost heap flops it is because the ingredients used were too dry.

The key to good composting is using ingredients that will give you the right carbon to nitrogen (C/N) ratio. Nitrogen is best introduced into compost heaps in the form of animal waste or well-chopped, soft green materials such as young weeds or lawn clippings. Carbon is mainly derived from aged, stalky material such as straw, old vegetable plants, dried grass, dried leaves and from wood waste such as shavings and sawdust.

The micro-biological process that occurs during composting is a form of rotting and decay, but without the unpleasant smell that often accompanies this process. A well-made compost heap is one in which the C/N ratio is anywhere between 25 and 30:1 as it creates an environment in which decay-causing bacteria (micro organisms) can live and reproduce at the highest rate of activity (see table below). As a result of this activity the ingredients are converted into a dark, cool, sweet-smelling matter called humus.

Humus is a non-living finely divided organic matter derived from microbial decomposition of plant and animal substances. It consists of about 6004 carbon, 64 nitrogen and smaller amounts of other substances such as phosphorous and sulphur. Humus is valued by farmers and gardeners because it provides nutrients essential for plant growth, increases soil water absorption and improves soil workability.

To speed the decay process, you can add leaves of yarrow or comfrey. Three or four chopped leaves of each herb to two cubic metres is sufficient to activate and accelerate the chemical reactions in the compost heap. It's a good idea to have three compost heaps, one being built another decomposing and a third one in use.

There are in the market, a number of different types of boxes, tumblers and barrels for making compost. Most times there is really no need to erect any structure to contain your compost heap. All you need is the bare earth on which your compost heap will sit. When required, because of exposure to extreme winds, rain or sun, some sort of holding structure can be provided. The time it will take for the compost to be ready will depend on different factors such as turning, climate and ingredients used. Normally in our temperate climate zone, a heap should be ready for use in twelve to sixteen weeks. The process can be speeded up by turning the heap more often. Also, adding comfrey or yarrow, or both, will accelerate the process.

A step by step guide to making compost:

1. Choose your ingredients. Work out your carbon to nitrogen proportions aim for 25-30 to 1.
2. Choose your site close to ingredients, close to water, not too much sun.
3. Collect your ingredients -have enough materials to build at least a 11/2 cubic metre heap.
4. Wet your ingredients until they feel like a well wrung-out sponge
5. Lay out a base and place sticks in a row or upend the books of a bale of hay to create a base that allows air flow.
6. Build the heap alternating different ingredients in layers. Keep the layers thin, say 150-200 mm for plant material and 75-100 mm for manure. Sprinkle soil, rock dust, seaweed, add yarrow or comfry or both. Strive to give it a dome shape
7. Keep wetting the heap - it is essential to maintain the moisture level.
8. Make the heap high enough, about 1.5m - use stakes to make air holes when heap is complete.
9. Protect the heap from the sun - protect the heap with a thick layer of hay so that it does not dry out.

Trouble shooting: If the heap fails to generate heat within 24 hours, pull it apart and build it again. If it hasn't started heating up by then it never will. Failure to heat up means that the necessary micro organisms have scorned the living arrangements you provided for them and failed to take up residence.

To find out why, ask yourself these questions:

1. Is the pile too wet or has it matted down so much that there is not enough air in it?
2. Are there too many bulky ingredients, or has the weather been hot and dry, so the pile has dried out and there is not enough moisture?
3. Is the pile too small, so it has too much surface area in relation to its internal area and is shedding heat too fast?
4. Are there too many nitrogen rich ingredients so that micro-organisms are being offered a diet that is like bread without any butter?
5. Are the layers too thick, so that microbes are being offered a diet of carbon or nitrogen in different places, but not both at once? Neither the bread nor the butter is very enticing on its own.

The most likely cures for these problems are the following:

1. Turn the heap more frequently to mix up the ingredients and incorporate more air;
2. Sprinkle the heap with water if necessary;
3. Add more green mulch and/or manure to boost the nitrogen content.
4. If your heap is very dry when you turn it, it probably means that it has too much surface area and so is losing moisture and heat too rapidly. The larger your pile. the smaller the ratio of surface area to internal volume
5. Another possibility is that the heap is the wrong shape. Sprinkle it with water and rebuild, aiming for a dome shape.

Approximate C/N ratios

Further Reading:- HADDON, Frank. A Practical Guide To Composting. Simon & Schuster, Australia 1993. TAYLOR, Inwid & Yvonne. The Compost Book. Reed, 1993

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