| The use of compost on the farm is generally limited to allowing weeds and the residues of previous crops to be dried out in the sun and then either heaping them in a convenient corner of the field until they are used in the preparation of mounds or ridges for the following crop or burying them as the mounds or ridges are prepared. |
On a garden scale, the preparation of a compost heap is more closely supervised since it is probably the only farm of organic material available, unless animal manure can be obtained.
The main factor to be considered in preparing decayed plant remains for use as an organic fertiliser is that the decay processes, which begin with a type of fermentation which produces heat, are brought about by bacteria of various kinds. In order to provide the most suitable conditions for this decomposition to take place, water and oxygen are required and the compost heap must therefore be kept well aerated and moist. Temperature is an important factor also, but air temperature in most tropical areas is high enough to promote rapid band erial decay.
Compost may be prepared by digging pits and throwing into them all organic residues as they become available, such as weeds, crop residues, kitchen waste and animal manure. The larger pieces should be chopped into lengths of 10-20 cm before being placed on the heap, or in the pit.
A second method is to partially sink the heap into the soil. The third method is to build the heap entirely above ground. These diagrams show the general construction of compost heaps and pits, their size will vary according to the size of the garden or farm, but they are generally in the region of 120-150x 120-150 cm and maybe up to 150 cm high. The main objective is to place the materials on the heaps, or in the pits, in layers, adding thin layers of soil or animal manure between the layers of vegetable material.
Wood ashes may also be added, if available. The thickness of each layer varies with the quantities and the types of material which are available, but may be from 5-10 cm thick. Where a wide variety of materials is being added at one time, these should be well mixed, since some materials decompose more rapidly than others. Mixing will ensure a fairly uniform rate of decay. Sulphate of ammonia, or other fertiliser containing soluble nitrogen can be sprinkled on the heap at intervals, as it is being made. This provides nitrogen for the bacteria at the beginning of the decomposition reactions. Animal manure has a similar effect. Heaps should also be turned at intervals of 2-3 weeks to promote bacterial activity and water should be added whenever the heaps become dry, since the bacteria require moisture for their life processes.