The Effect of Different Substrates Found in Zimbabwe on the Growth and Yield of Oyster Mushroom Pleurotus Ostreatus

Abstract

The research was carried out to investigate the effect of different substrates on the growth and yield of P. ostreatus. Locally available agricultural wastes such as saw dust (S1), cotton waste (S2), wheat straw (S3) and corncob (S4) were tested for parameters such as days required for spawn run, primordial formation, harvest days, total yield and biological efficiency. Biological Efficiency (BE) was calculated as the ratio of fresh fruiting body weight (g) per dry weight of substrates (g), expressed as a percentage. Before substrates were used in this study they were subjected to nutritional (C, N, P, K, Ca, Mg and Zn) analysis. The highest yield of 1275.45 g was obtained in saw dust and the lowest yield of 1058.7 g was obtained in cotton waste. The highest carbon to nitrogen (C/N) ratio was found in saw dust (53:0.1) and the least C/N ratio was found in cotton waste (39:1). There were 19 spawn run days in saw dust and 24 spawn run days in cotton waste. Stem width (2.6 cm) and cap diameter (9.7 cm) were greatest in cotton waste and low in saw dust with stem width (2.3 cm) and cap diameter (7.4 cm). Substrates with a higher C/N ratio had the greatest yield and biological efficiency. The higher C/N ratio favoured mycelium growth and lower carbon to nitrogen ratio favored fruiting body growth. In this study saw dust had the highest C/N ratio and it had the greatest yield and low spawn run days yet cotton waste had the least C/N ratio but its fruiting body measurements were very high. There was no significant difference at p≤0.05 between wheat straw and corn cob in terms of growth parameters and yield as their C/N was significantly high at (44:1) and (49:1) respectively. The results signifies that apart from soya beans and maize stalk which were widely used by farmers as substrates of choice, saw dust, cotton waste, corn cob and wheat straw were good alternatives for the growth of P. ostreatus mushrooms. Saw dust was very good in the total yield obtained but cotton waste had the best quality of mushrooms with very big stipes and cap diameter. These locally available substrates in Zimbabwe were recommended for use by small scale farmers for sustainable production of oyster mushrooms as they produced good yields at low cost.