COMPOST

Agricultural Uses

Compost is an organic manure formed by the slow decomposition of (a) various plant or animal residues, (b) wastes (like dung, crop waste, slaughterhouse waste, etc.), (c) pre-sorted household wastes, and (d) sediments of sewage purification units. Composting is the process of preparing compost for soil conditioning by the microbial degradation of organic waste, by using aerobic and anaerobic micro-organisms to hasten decomposition. The carbon to nitrogen (C:N) ratio of the material, its water content, aeration, pH and temperature, etc. regulate the prevalence and multiplication of the microbial population and the rate of decomposition of the material.
Organic material is decomposed by aerobic saprotrophico rganisms, mostly fimgi and bacteria. Some decomposition is also carried out by detritivores. Decaying organic matter is used as manure.
Anaerobic composting is a method of composting farm wastes with insufficient aidoxygen supply. When decomposable raw material like farm or crop wastes is filled in composting pits to a height of 40to 50cm and decomposed by micro-organisms in an anaerobic environment, the process is called anaerobic decomposition. The compost is generally ready within 4 to 5 months and contains 0.8 to 1 % nitrogen.
Conventional methods of composting require a long period to produce good compost, often 8 weeks or more. There is a combined action of organisms like earthworms, bacteria, nitrogen fucers and cellulolytic as well as lignolytic fungi, which hasten the process of composting. Such decomposition of organic matter results in a product which is rich in humus and has a low carbon to nitrogen ratio. In recent years, there has been considerable interest in the use of earthworms for composting. This practice is called vexmicomposting
There are different methods of composting, depending on the availability of raw materials and specific requirements of the region. For composting, the organic matter is piled in a specially built pit. Decomposition is facilitated by keeping the pile warm and moist, and encouraging the growth of micro- organisms. After a specified period of time, the compost is ready for use. If the organic matter is deficient in nutrients, these are added in the form of nitrogen, phosphates, manure and animal wastes.
Compost is produced primarily from plant residues is called artificial manure or synthetic manure. Compost produced by a partial aerobic fermentation of diverse organic material like cattle dung, urine, crop residues, farm waste or agricultural waste (such as weeds, straw, groundnut husks, etc.), is called rural compost. If produced from materials of urban origin - like street sweepings and dustbin refuge - the product is known as urban compost.
When sewage sludge and municipal garbage are composted, municipal compost is produced. This compost can cause health hazards because the organic and inorganic waste material may carry pathogens, viruses and parasite eggs. This problem can be partially solved by the self-heating of compost during decomposition. But heating does not remove non-organic material like lead, strong acids, etc. which harm plants. Some toxic substances, harmful to plants and animals are also produced during composting.
Composts are comparatively less effective than fertilizers, as they contain less than 2% NPK, half of which is mineralized during the growing season.
A rural compost generally contains 0.5 to 1.0% nitrogen, 0.2% phosphorus (as P₂0,) and 0.5% potassium (as K₂0), whereas urban compost has about 1.5 to2.0% nitrogen, 1.0%P₂0₅and 1.5% K₂0
. Compost can be made entirely from plant materials. Some examples are kitchen waste, plant litter, garden pruning and industrial waste of plant origin.
Compost has numerous uses, depending on its quality. High quality compost can be used to replace the lost topsoil in farms. The amount of compost needed for this purpose is enormous; 160tons of compost is required for 2.54 cm of topsoil over one hectare of land. Cornposting the organic wastes of a community of one million people could produce an estimated 600tons of compost daily. Compost is widely used in nurseries and landscaping industries and in inland reclamation. Sanitary landfills also need compost or soil between the trash layers and as a cap on the top, once the landfill is closed.