The home-built compost heap is often the best and if constructed correctly in the first instance can provide a long-term, easy-to-manage environment for successful composting.
The following method has been used by gardeners for many years and I have found it very reliable. It can be adjusted to suit your own garden.
The size and shape of the heap is one of the main aids to success, so some careful thought should be given to this. For a garden of less than, say, 400 square yards (metres) a compost head of 4 ft (1.2 m) square and high is required for one year’s composting, and, as composting takes up to two years, two containers will be required.
The container can be made of wire netting simply supported by strong posts at the corners, or of planks of timber, bricks or concrete blocks, but if these more solid materials are used provision for the free passage of air through the sides must be provided. One side of the container should be detachable to allow easy access to the finished compost. However, when I was an apprentice we built compost heaps 10 x 10 ft (3 x 3 m) and up to 8 ft (2.5 m) high without surrounds and it may not be necessary to provide any container, particularly where there are large amounts of material to be composted.
Free drainage of the heap is important and to achieve this soil on which the heap is to stand should be single dug. This also ensures that the soil organisms that will aid decomposition can gain entry to the base of the stack and work their way up through the lower layer of the material to be composted.
As material becomes available it should be placed in an even layer on the dug soil within the containing frame. Once the layer has reached 12 in (30 cm) a 1 in (3 cm) layer of garden soil is placed over the composting material. The soil can come from any area of the garden and is used to ensure that the soil organisms needed for decomposition are transported from the soil to this higher level of the compost heap. To ensure that these organisms have adequate food in the form of nitrogen, a small sprinkling of composting activator such as Garotta is added, as recommended on the packaging.
This layering of composting material, soil and activator is continued until the container is full or the winter arrives and active composting ceases.
As the heap is built up it will sink and heat up, good signs that it is working as planned. Because the soil organisms need moisture the heap should not be covered.
For the best weed-free compost the heap should be turned in the winter following its formation. For this a second container should be built into which the first year’s compost is turned and restacked. The moving aerates the compost and ensures even decomposition. There is a temptation to use the compost at the end of the first year as decomposition is often well advanced by then. However, the compost may contain large amounts of unsterilized weed seeds that, if spread over or dug into the soil, will germinate and cause real problems. It is not necessary to introduce more soil in this restacking but feeding every 12 in (30 cm) with a sprinkling of Garotta will promote decomposition.
By the end of the second autumn a useful renewable supply of organic material will be available. Just one more precaution is needed before the compost is finally used, to ensure that the weed seeds do not cause a problem: the top 6-8 in (15-20 cm) and a 4-6 in (10-15 cm) slice from the outer edges is removed and placed on next year’s heap, as it may not have been fully sterilized.
In larger gardens or in those with limited space it may be worth considering composting below ground. Suitable sites are at the back of shrub borders and other hidden but accessible places. Pits are dug 4 ft (1.2 m) wide and 4 ft (1.2 m) deep and the bottoms of the pit dug over to ensure good drainage. The pits are then filled in layers as fro the standard compost heap until full, or until the winter comes and active composting ends. Compost produced in this way normally does not require turning and if the siting of the pits is chosen with care the compost can be made near where it will finally be needed. The only extra precaution that is required is to provide a strong cover to prevent anyone falling in by accident, but see that the cover allows rain to enter the composting material from above.