Abstract:
Coir dust, an agricultural by product, can be used as a plant growing medium after 
amendment of chemical properties. C: N ratio implies the presence of Carbon in the 
medium in relation tp available Nitrogen. It should be less than 30% to minimize 
the competition between micro organisms and higher plants for available Nitrogen. 
An experiment was design to reduce the initial 55.46% C: N ratio of coir dust by 
using Oyster mushroom {Pleurotus ostreatus). Mycelium growth rate on coir was 
compared with traditional substrate, saw dust, There were no significant difference 
between mycelium growth rate or contamination percentage between coir dust and 
sawdust. Bag and bed method were used to test the effectiveness of C: N ratio 
reduction at field conditions. C: N ratios of both methods were checked in weekly 
intervals. After six weeks initial C: N ratio was reduced to 33% by bed method and 
26% by bag method. According to the results oyster mushroom can successfully be 
used to reduce C: N ratio of coir dust by bag method.