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In this article we will discuss about:- 1. Definition of Compost 2. Process of Composting 3. Factors 4. Roles.
Definition of Compost:
Compost is defined in the Oxford Advanced Learner’s dictionary as the process of mixture of decayed organic matter, manure, etc. added to soil to improve the growth of plants.
According to Biddlestone (1973) composting is the decomposition of heterogenous organic matter by a mixed microbial population in a moist warm aerobic environment. Incomplete microbial degradation of organic waste, where the microbial processes vary from aerobic to anaerobic form are stated as compost.
Process of Composting:
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For making the compost, the crop-residues are degraded in specially designed pits soak to conserve nutrients in a confined environment where cattle dungs, farm wastes (arranged in layers) and urine are allowed to remain for desired periods. The contents are either exposed to air or loosely covered with a mud pack so as to prevent water logging during rainy season.
After 6-8 months incubation, the material is ready for use in the farm as an organic fertilizer. Most compost deliberately consists of a mixture of pectin, hemicellulose, cellulose and lignin.
The compost may contain a number of chemical fractions each with its own decomposition characteristics. Usually the process of compost formation is aerobic. It is intended to produce a product compost which can be used as a organic fertilizer and soil conditioner.
Factors Affecting Composting:
These are several factors that affect composting:
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(a) Microorganisms:
The selection of suitable microbes depends on the type of composting process i.e. aerobic or anaerobic, type of raw material, etc. The efficient cellulolytic cultures, such as species of Aspergillus, Trichoderma, Penicillium and Trichurus accelerate composting for efficient recycling of dry crop wastes with high C:N ratio and reduce the composting period by about 1 month.
Enrichment of partially composted crop wastes can be achieved by Azotobacter and phosphate solubilizers to improve the nitrogen as compared with controls.
Moreover, the presence of a mixture of anaerobic forms of microorganisms in dung or biogas slurry proved potent in making compost. Actually, the compost carries agriculturally useful microorganisms which aid in the improvement of soil fertility.
(b) Soil:
The soil can be defined as a natural medium for plant growth composed of minerals, organic materials and living organisms. The biological activities and microbial metabolism in the soil contribute to its texture and fertility.
(c) Organic Matter:
The amount of organic matter present in any soil determines its natural suitability for plant cultivation. The value of compost has not only in its N P K content but also in the substantial quantities of humus which are essential for maintenance of soil organic matter and fertility levels in tropical and sub-tropical soils.
Roles of Compost:
Composting reduces the soluble nitrogen contents of agricultural wastes. If these wastes are spread directly onto land the highly soluble nitrogen compounds can be easily washed into water courses.
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Composting also results in phosphorus compounds becoming bound up in new microbial cells so that run-off can be avoided. Higher crop yields have also been claimed for composted versus directly applied animal manures.
The incorporation of organic remains in the form of compost, farmyard manure, cereal residues and green manure is known to influence favourably the physical, chemical, physicochemical and biological properties of soil.
Various workers have observed that composting is one of the oldest solid waste treatment methods known to man. Although compost making has been practised since Biblical times but modern interest probably stems from an extended visit to China, Japan and Korea in 1909 by Professor R.H. King of the U.S. Department of Agriculture.
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His observations were further studied by Sir Alberts Howard, a botanist employed by the Indian government, who developed the Indore composting process. The process is involved the construction of pits (30 feet long, 14 feet wide and 2 feet deep) to conceive heat and moisture, except during the monsoon season when they were built above ground. The heap was composted by building up of plant material, animal manure, dust soil, ash and moisture. The heap was turned after 16, 30 and 60 days and carted to the fields after 90 days.
Subsequently, the process was improved and developed. It has been shown that, when compared to inorganic fertilizers of similar nutrient value, compost has increased crop yield by as much as 10%. Further, compost has the additional advantages that they add humus to the soil and improve aeration and water holding capacity to the soil.
