Comparison of mushroom yields obtained from fresh grain spawn and spent mushroom subtrate in oyster mushrooms Pleurotus HK 35

Abstract

This study investigated the possible use of spent mushroom substrate as spawn. It was conducted at the University of Zambia in May 2002 using Pleurotus HK 35 strain and giant star grass (Cynodon Plectostarhycum) as substrate. The substrate was pasteurised by immersing in hot water at 70° C for 2 hours. Fresh grain spawn and spent substrate post third flush (55 days) were inoculated into the substrate and incubated.In this study the mean time to full colonization for fresh grain spawn and spent substrate was 23 and 33 days while the mean time to first flush was 31 and 50 days, respectively.The mean yields per flush in fresh grain spawn were 417.70 g, 334.0 g and 90.42 g of mushrooms, respectively. In spent substrate, there was one flush with a mean yield of 97.35 g mushrooms, with only one substrate out of 10 producing a second flush with a yield of 288.81 g. There was no third flush in spent substrate. The mean flushing intervals in fresh grain spawn 9.7 and 10 days respectively, whereas in spent substrate there was mean interval of 16 days between full colonisation and first flush. The total mean yield for fresh grain spawn was 910.10 g mushrooms, that of spent substrate was 126.20 g of mushrooms. The contamination rate in fresh grain spawn 10 % as opposed to 100 % in spent substrate, while were responsible for the reduction in yields. It was thus concluded that spent mushroom substrate cannot be used as an alternative to fresh grain spawn.