THE EFFECT OF COMPOSTING SUBSTRATES ON THE GROWTH, YIELD AND NUTRIENT CONTENT OF THE OYSTER MUSHROOM, PLEUROTUS OSTREATUS (JACQ. EX FR.) KUMMER

ABSTRACT The effect of composting substrates prepared from four agricultural wastes: corn cob, oil palm fruit fibre, rice husk and sawdust on growth, yield and nutrient content of oyster mushroom, Pleurotus ostreatus, (Jacq. ex Fr.) Kumer was investigated. One set of the substrates was decomposed and the other set was not. The mother spawn, obtained from oyster mushroom fruit body tissues and spores from two sources and a spawn from a third source, cultured on Potato Dextrose Agar medium grew best at 30 °C and in total darkness. Sorghum grains gave the best growth as a multiplication medium. Spawns grew best on decomposed substrates than on undecomposed substrates. Decomposed substrates gave higher yield than the undecomposed substrates. Oil palm fruit fibre produced the highest yield, followed by corn cob, sawdust and rice husks in that order. The decomposed substrates contained higher levels of nutrients than the undecomposed substrates. The types of substrate also determined the level of nutrients in the mature oyster mushroom. Thus, fat and protein levels were highest in mature fruit bodies obtained from oil palm fruit fibre while total carbohydrates were highest in fruit bodies obtained from rice husk. Insoluble lignin breakdown in all four agricultural wastes by Pleurotus ostreatus was highest in rice husks, 67.01 – 78.78 %; followed by sawdust, 39.70 – 50.93 %; oil palm fruit fibre, 30.85 – 35.11 %; and lowest in corn cob, 11.32 – 22.32 % while breakdown of soluble lignin remained generally the same for all the four substrates (0.0757 – 0.0780 mg/g). Use of agricultural wastes as substrates for oyster mushroom production can solve the problem of malnutrition and pollution of the environment.