Composting is a natural process of rotting or decomposition of organic matter by microorganisms under controlled conditions.

Raw organic materials such as crop residues, animal wastes, food garbage, some municipal wastes and suitable industrial wastes after composting enhance their suitability for application to soil as a fertilizing resource. In addition to being a source of plant nutrient, compost also improves the physiochemical and biological properties of the soil.

As a result of these improvements, the soil becomes more resistant to stresses such as drought, diseases and toxicity.

Composting helps the crop in improved uptake of plant nutrients and possesses an active nutrient cycling capacity because of vigorous microbial activity indirectly leading to pathogen suppression in soil. These advantages manifest themselves in reduced cropping risks, higher yields and lower outlays on inorganic fertilizers for farmers.

In recent years, decomposition of agricultural wastes such as coir pith, banana sheath (dried), sugarcane trash, millets and pulse waste, cotton stubble with white rot fungus (Pleurotus sp.) is gaining importance.

These wastes are decomposed with any one of the white rot fungi P. eous, P. platypus, P. djamor or P. sajorcaju by layer system. One layer of agricultural waste at 100 kg is spread uniformly in an area of 4 x 3 m2 under shade.

Culture of P. djamor at 200 gms is applied over the substrate. Another 100 kg of substrate is spread over the first layer and urea is applied at rate of one kg to the substrate.

This sandwiching is repeated to make a heap of 1,000 kg substrate with such 20 layers. A total of one kg of the fungus and five kg urea is required to decompose 1,000 kg waste.

Water is sprinkled twice a day to maintain 50 -60 per cent moisture level. The heap is allowed to decompose for a month after which a turning is done. The waste undergoes degradation within 45 days. It has a narrow carbon : nitrogen ratio of 20:1 which can be used as organic manure.

(M.Theradimani, Associate Prof & A. Sankaralingam, Head, Department of Plant Pathology, Agricultural College and Research Institute, TNAU, Madurai-625 104, e mail :, Phone : 04522422956 extn.242, Mobile : 9443432752.)