Effect of delayed-release supplements in grain-based substrate on yield of the mushroom agaricus bisporus

Non-composted grain-based substrates mixed with delayed-release supplements were used as a mushroom substrate to test suitability for mushroom production as a replacement for the environmentally problematic composted substrate. Five delayed-release supplements (S41, S44, Promycel Target, T6, and T7) were added at seven levels (0%, 5%, 10%, 15%, 20%, 25%, and 30%) to a non-composted substrate composed of commercial millet grain spawn. Overall, mushroom yield, substrate bioefficiency (fresh weight of mushrooms / dry weight of substrate), and mean mushroom weight increased with the addition of the supplements when compared to the 0% supplement treatment. The highest mushroom yield and substrate bioefficiency were observed for the 20% S41 treatment, which produced 13.7 kg m _-2 of mushrooms with a corresponding substrate bioefficiency of 133.7%. The observed yield and substrate bioefficiency were considerably higher for S41 than for Promycel Target, S44, T6, and T7. Mean mushroom weight was highest for the 20% T6 treatment (34 g), and higher mean mushroom weights typically corresponded to treatments with lower mushroom yield. Substrate temperatures for the different treatments were either similar to or lower than the ambient air temperature. Hence, substrate overheating as encountered in compost-based substrate was ruled out as being the reason for lower yields observed at the higher rates of supplementation.