Rules of Composting


THE word ‘compost’ is used by gardeners to denote two quite different substances. The first is a mixture of soil, peat and sand which is used in potting and is generally called a potting compost. The second is vegetable waste of all kinds which has been properly rotted down in a heap or pit together with an activator, and in consequence has formed a blackish-brown crumbling material very near to humus. It is this kind of compost that is dealt with here.

In the past, gardeners were able to buy large quantities of farmyard or stable manure and so composting was not generally practised. But in present-day conditions such manures are no longer readily available.


Many things can go on to the compost heap: the tops of peas and beans, fresh hedge clippings, pea pods, tea leaves and coffee grounds, banana peel, fluff from the vacuum cleaner, straw, lawn mowings, fallen leaves, and even well-soaked newspapers. It is important not to use obviously diseased material.

Whatever the material it must be helped to rot down properly by using some type of activator. This may be excreta from some animal, the droppings from birds such as poultry or, when these are not available, fish manure or a proprietary activator. The compost heap is built up in layers of the vegetable waste with a sprinkling of the activator and soil in between the layers.

It is often easier to make a bottomless bin of old planking or of wire netting into which the vegetable waste can be collected and raked level. The size of the bin will depend on the size of the garden. For a garden of half an acre the bin may be 6 ft. by 6 ft. with perhaps a reserve bin nearby. For a garden of an acre it may be 8 ft. by 8 ft. and have two reserve bins alongside.

There is all the difference in the world between a rubbish heap and a compost heap. A rubbish heap is merely a collection of vegetable waste, and may well be the breeding ground for pests and diseases, as well as a place where weed seeds are stored but not killed. In a properly made up compost heap the temperature will rise to 180° F. (82° C). It is then that the actinomycetes break down the more resistant proteins and carbohydrates in the heap. The temperature may remain high for a month and then, as the heap cools down, the bacteria complete the task of manufacturing plant foods.


For a good compost heap, the layers of refuse should be 6 to 8 in. thick and should be trodden down moderately firmly. If the material is very dry, water may be applied before the activator is put on. If it is necessary to use very tough material such as cabbage stumps it is best to break them up first on a chopping block to pulverize them. They should then be intermingled with grass mowings or similar material to help build up heat. Healthy woody material can be included. Unhealthy woody material should be burnt and the ashes added to the heap. Never burn any soft material. Rhubarb, laurel or elderberry leaves can be added to the heap, even though these three are thought by some people to produce bad effects.

Apply the activator at the rate of 3 oz. per sq. yd. to every 6-in. thickness of waste. If the soil of the garden is known to be acid then activate three of the 6-in. layers with fish manure and treat the fourth 6-in. layer with carbonate of lime at 7 oz. per sq. yd. Build up the heap gradually day by day and week by week as the vegetable waste becomes available. When the heap reaches a height of, say, 6 ft., put a 6-in. layer of soil on the top, thus providing a capping to help keep in the heat.

When very soft materials are used, such as lawn mowings or cabbage leaves, provide a ventilation shaft by driving a post 3 in. across into the ground in the centre of the bin or pit, pile the vegetable waste round it layer by layer and activate in the normal way. When the heap reaches its-normal height pull out the post, thus leaving an air shaft through the middle. This is seldom necessary for small heaps but is quite a good thing for heaps that are 12 ft. by 12 ft.

Some gardeners believe that the compost heap should be turned at the end of three months, but the heap should rot satisfactorily without any attention at all. It will probably be ready for use at the end of six months, though it need not be used for six years. If the outsides have not rotted down properly, cut them off with a spade, just as the black part of a burnt cake is cut off with a knife, and put them on the reserve compost heap for rotting down.

When the compost is ready to use, it should look like earthy mould or moist peat. It should be dark brown or black, perfectly sweet smelling and show no traces of the orginal materials. Eighty-five per cent of it should pass easily through a ^-in. sieve.

When it is properly made, compost can be twice as valuable as dung, for in addition to containing actual plant food it is alive with millions of microorganisms. It will also contain most of the minor minerals, known as trace elements, which plants require.

These are the principles of compost making. There are two other methods that are often used.

The first is the Indore Method: for the small garden make a bottomless box to contain a heap 4 ft. by 4 ft., and 3 ft. 4 in. high. Such a heap will provide 2 cubic yds. of good compost, weighing l ton. Bolt or screw three sides of the box together, and make up the front with loose boards slipped into position as the box is filled. Where possible, make a reserve bin.

Cut all the vegetable waste into lengths of a few inches and put it into the box with one-third or one-quarter of the same volume of manure. Incorporate a little soil at the same time. If poultry or rabbit manure is not available then use hoof and horn meal or dried blood at the rate of l to 2 per cent of the dry vegetable waste.

When the box is full, make three holes vertically through the mass with an iron bar to improve the supply of air. Cover the top with sheets of corrugated iron to keep out the rain. After six weeks dig the material out and stack it on a convenient site where it can ripen for another six weeks. Four tons of compost per year can be made in one of these l ton boxes.

The second method is to make the bins with old boards (old railway sleepers are excellent as they are thick and help to retain the heat), wire netting or bales of straw. The straw can later be put on the heap.

Make the bins 6 ft. by 6 ft. with open ends for ease of access, and intersperse the 6-in. layers of waste with fish manure at 2 oz. per sq. yd. whenever available add the urine and excreta from any animals that are kept. Once a week or so, in the summer, give the heap a good watering. When it is 4 ft. high plunge a long-tined fork into it in several places and move it backward and forward to provide aeration.

At the end of six months the heap will be ready for use. Skim off the top 9 in. or so and also the sides, if they are not fully decomposed, and put them into the reserve bin for further rotting.

If the garden soil is acid, use hydrated lime instead of fish manure as the activator, at 4 oz. to the sq. yd. for every 2 cubic ft. of waste.


Apply compost at the rate of at least a gallon bucketful to the sq. yd. Each year. Do not dig it in deeply, but either fork it or distribute it with a rotary cultivator through the top 3 or 4 in. of soil, or apply it as a top dressing or mulch on the surface of the ground. The worms will pull much of it in, thus aerating the ground. By using compost the soil will not dry out so readily, the tilth will be improved, and there will be ample humus to feed seedling plants.

11. September 2013 by admin
Categories: Gardening History, Plant Biology, Top Tips | Tags: , , , , , , , , , , , , | Comments Off on Rules of Composting


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