Composting is a biological process that converts organic matter into stable humus like product under controlled conditions. Compost is the dark brown crumbly material that is produced when a collection of plant and animal material is decomposed into fine organic matter and humus.
Method of Composting
Different methods of composting like aerobic, anaerobic and vermicomposting are followed for preparation areas, aerobic method of composting is found to be most appropriate and efficient method of composting farm wastes.
Material Required for Composting
- Farm wastes: Any farm wastes like cherry husk, coffee pulp and other crop residues like straw etc. would form the basic raw etc. would form the basic raw material for compost preparation.
- Animal wastes: cattle shed wastes containing ding and urine, goat droppings, piggery and poultry wastes.
- Green material: Any green plant material (preferably of legumes) like leaves, shade tree lopping, weed biomass etc.
- Compost enrichers: Rock phosphate, bio-fertilizers (Azotobacter, Azospirillum, ‘P’ solubilisers, Trichoderma, VAM) could be used for enriching the compost.
- Decomposition enhancing cultures: Phanerocheate chrysosporium, Trichoderma viride, Aspergillus awamori, Pleurotus sajarcaju, Bacillus, Pesudomonas cultures and yeast cultures.
- Nutrient additives/enhancer: Neem cake, pongamia cake, cow dung slurry, butter milk.
Materials to be Avoided
- Residue from crops sprayed with pesticides or herbicides.
- Materials diseased with rusts and viruses.
- Hard prickles or thorns.
- Persistent perennial weeds. To avoid any chance of these weed spreading, they should be killed by burning or spread in the sun till they dry out completely
- Paratoxic materials like metals, rubber, glass and plastics.
- Large quantities of newspaper and cardboard will greatly slow the rotting process.
Selection of site
Composting should be done under shelter of trees to prevent drying of heaps and to preserve moisture.
Size of compost heap
The compost heaps should essentially have 1.5 to 2 m width and about 1 m height. They can be of any convenient length depending upon the availability of raw materials.
Preparation of the materials
Although many materials can be used directly, some may need pre-treatment before composting, as given below.
- Material containing high moisture content (e.g. coffee pulp) should be allowed to wither a little.
- Rough and coarse materials such as stalks of paddy should be broken or chopped before use. The best way to break these materials is to spread them over cattle shed. It will also help in collecting the urine and dung properly.
- Dry woody material like cherry/parchment husk should be made moist before being added to the hep, preferably soak them in water for several days.
- Shortage of easily decomposable materials in the compost heap, the composting process will be very slow. If excess, the heap will become acidic and create nasty smell the composting process will be slow resulting in poor quality.
Construction of Heap
The compost heap needs to be made up layer by layer by spreading different raw material as described below.
Step 1: Lay a lattice of old braches or fibrous material like coconut shells etc. at the bottom for providing aceration and preventing water logging. This layer is called as base layer.
Step 2: over the base layer, spread the farm wastes (like cherry husk, coffee pulp, crop residues etc.), green matter (like leaves of shade trees, green manure crops like Daincha, Sesbania, any crop residues and weed slashing etc.) and animal wastes (cattle shed wastes ) layer by layer alternatively till the suggested height. The thickness of each layer should be around 10 to 15 cm.
Step 3: sprinkle cow dung slurry or bio-gas slurry (2 cm) between each layer to hasten the composting.
Step 4: sprinkling of supernatant liquid from well-fermented curd is also found to be highly effective, especially for composting coffee wastes like cherry husk and coffee pulp.
Time for Turning of Heap
- The first turning should be done after 2 to 3 weeks of heaping.
- The subsequent turning of the heap is followed by three weeks after the first turning.
- Depending upon the temperature and kind of residues, turning is done two to three times at an interval of about three weeks.
- If the heap is prepared using residues having different C:N ratios with proper aeration and moisture, only one turning after 3 to 4 weeks would be sufficient.
Advantages of Turning the Heap
- Turning improves the aeration of the heap.
- Removes excess carbon dioxide concentrated inside the heap.
- Gives a chances to check the moisture content of the materials and if the material is too dry, it should be watered.
- Help is evenly mixing of undecomposed materials to get good quality compost.
Maturation of Compost
- The time required for the heap to mature and become good compost, depends on local climatic conditions and materials used.
- If the weather is warm, the heap is moist, well aerated and good combination of materials is used for building the heap, the compost is ready in three months time.
- In colder or dryer conditions and dominance of materials with high C:N ratio, heap usually takes six months to ripe.
- Well composted material is coarse varies from dark brown to grey colour , giving an earthly smell.
- The volume of the mature heap is reduced to half of the original.
Application of Compost
In coffee, application of compost at least once in 2 to 3 years at the rate of 5 kg and 10 kg is recommended at 5 to 7.5 t ha-1 ( 2 to 3 t ac-1) for Arabica and Robusta respectively. The application of compost would improve soil texture and structure, minimizes soil erosion by binding soil particles, increases water holding capacity of the soil, provides ideal environment for growth of beneficial microorganisms in the soil and increases the use efficiency of applied nutrients.