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Composting
Farmyard manure is the oldest manure known to mankind and is made up of solid excreta or dung of animals, urine and plant remains which are allowed to decay with the help of soil microorganisms capable of decomposing complex organic debris into substances that the easily assimilated by plants. The manorial value of farmyard manure depends on the nature of raw materials used and the extent of decomposition by soil microorganisms.
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Compositing farm residues and night soil has been practiced for long in China and India. In China, the compost pits dug in soil have usually dimensions of 35 m x 25m x 15m (L x B x H). The pits are filled layer by layer and each layer is about 15cm thick. The bottom layer (layer No.1) consists of green plants and aquatic weeds available on the farm followed by silt-straw mixture (layer No.2) and animal excreta (layer No.3). The layering is repeated until the pit is filled. Finally, a layer of mud is made on top of the pit in such a way that water of about 4 cm depth is maintained on the surface to create anaerobic conditions which helps to reduce losses of nitrogen.
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In a time span of about 10 weeks, the mud plaster is dismantled and the contents of the pit are turned over or mixed with superphosphate and water (if necessary); At the end of 3 months, the compost is ready for use on the farm. The compost may have a CN ratio of 15-20 and organic matter content of 8-10 per cent. A compost is considered superior if the CN ratio is 20 or less and the organic matter content is around 30-60 per cent.
In India, the pit method is also practiced without any water logging in an elevated place often protected by a shed. The layering at the bottom is usually the urine-soaked bed in the cattle shed. The bed is made of farm materials such as vegetable wastes, fodder remnants, green matter etc.
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The bed layer is sprinkled with a slurry of cowdung and mixed with well decomposed manure from the previous batch. This sort of layering and sprinkling with cowdung slurry is repeated until the pit is filled. The compost pit sits for a period of 2-3 months within which time the contents are turned over or stirred three times.
Composting can also be done by the heap method in which the base material on a hard ground consists of hardwood materials coming from cotton and pigeonpea stalks followed by layering with farm residues such as leaves, hay and garbage.
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The heap can be rectangular in shape. After wetting with water, the heap is mud plastered and allowed to sit. Within a period of 2-3 months, the heap is broken, materials turned or stirred and again mud plastered. The final product becomes a heap of well decomposed organic matter.
High temperature composting is done in China by heaping alternate layers of night soil, urine, wage, animal dung and chopped plant residues. The base material consists of hard stalks of crops and this is followed by layering with other materials. Water is added at optimum levels. The entire heap is shaped finally with mud plaster taking care to insert bamboo or maize stalks into the mud covered heap all the way to the bottom of the heap.
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After 24 hours, the bamboo poles or maize stalks are withdrawn to leave behind holes for ventilation. Within 4-5 days, the temperature in the heap reaches 60-70°C when the holes are closed and sealed with mud plaster.
Composting
After a period of 2 weeks the mud plaster is broken and the contents mixed followed by resealing with mud plaster. At the end of 2 months, the decomposed compost free from pathogens is ready for use on the farm.
The finished compost can be enriched with finely powdered rock phos¬phate and inoculated with non-symbiotic nitrogen fixers such as Azotobac¬ter, Azospirillum and phosphate dissolving bacterial or fungal species such as Pseudomonas, Micrococcus, Bacillus, Flavobacterium, Pencillium, Fusarium, Asppergillus etc.
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