There are different methods of composting organic materials. For the purpose of this class we are going to concentrate only on Indore method. Here, compost are produced in:
- Pit – during the dry part of the year; and
- Stacks on surface or aboveground – during the rainy season.
In either of the method, the heap is built to a height of 1.5 m and having a base of about 40 m2. A heap with the such dimension will require nearly 20 tons of organic waste material and should produce 6 to 8 tons of compost per batch.
It should be possible to produce 2–3 bathes per year in a pit and normally one batch for a stack. A smaller dimension can be adopted depending on the available materials to be composted. A good basic size is 2 to 2.5 wide and 1.5 to 2m in height while the length will depend on the quantity of the available organic materials.
It is strongly advised to start with a heap greater than 1 cubic meter otherwise the temperature in the heap remains low and the decomposition is too slow and incomplete.
1. Setting up the heap
In setting up a compost heap, it is important to start the heap with a foundation of coarse materials such as twigs and sugar cane stalks. The outside can easily flow in under and the excess water flows away more quickly.
Materials such as straws and dried leaves are then added on top of the coarse materials. These materials are called the brown materials. Next is to add materials that are easily decomposed such as fresh leaves, weeds grasses, etc. these materials are called the green materials.
In good composting practice, the ratio of brown materials to green materials should be 1:2. That means to each part of brown material you add two parts of green material. This is then followed by the addition of animal manure.
After this, water is sprinkled on top of the set up before another set of layer is built up. The individual layer should not be more than 10 cm of the plant materials and 2 cm for the manure.
Read Also: Process of Composting Organic Waste Materials
As stated earlier, air channels should be inserted in the heap by putting twigs upright in the heap as indicated in figure 5 above. It should be remembered microorganisms are the ones that carry out this decomposition process. Hence it is necessary to add them in the heap.
2. Additives
Compost is essentially a soil conditioner containing a fairly low level of plant nutrient. Where food production needs to be increased and mineral fertilizer can be afforded, then there is an incentive passing it through composting process.
Care must be taken to avoid adding excessive nitrogenous fertilizer is not added which can lead to nitrogen loss as ammonia. Addition of phosphorus has a beneficial effect on the compost heap.
The composting process makes phosphate more water soluble and hence more available to plants. Cheap phosphate rock can be used instead of more expensive superphosphate, which has been chemically treated to make it more water-soluble.
Moreover, he addition of phosphate rock or calcium phosphate of 2 to 3 % by weight has been found to be beneficial in speeding up the composting process and in nitrogen conservation.
Addition of inoculants such as bacterial culture will be beneficial to the compost heap as it adds microorganisms to the heap. It has been indicated that inoculating compost heap with suitable nitrogen fixing bacteria, Azotobacter, in the presence of phosphate rock will significantly increase the nitrogen content of the final compost.
3. Covering the heap
In times of heavy rain or in an area of heavy rains, the heap has to be protected against excess water. This can be done by covering with a simple roof above the heap or even simpler by covering with layers of leaves, cloth, plastic materials, and so on. If plastic materials are used, then cover the top only so that air can penetrate through the sides.
Trenches around the heap should be created to facilitate run off of excess rainwater. Covering the heap with the material mentioned can also be advantageous in dry areas. It prevents excess evaporation of moisture from the heap and it dries out less quickly.
Read Also: The Practice of Composting Organic Waste Materials
