Extending the productive lifespan of oyster mushroom substrates using external nutrient supplementation

Abstract

In conventional mushroom cultivation, the productive lifespan of mushroom bags typically ends after approximately 3.5 months due to nutrient depletion within the substrate. At this stage, farmers discard spent mushroom substrate (SMS) and begin the labor-intensive process of preparing new cultivation bags. This study investigates whether external nutrient supplementation can rejuvenate SMS and extend harvesting in American oyster mushroom cultivation. The effects of two external nutrient media, pasteurized yogurt drink (PYD) and glucose solutions (GS) were assessed at three concentration levels each (2%, 3%, and 4%), alongside a control group (water only). A total of 133 SMS bags were used across all treatments, with 19 bags allocated per treatment, following a completely randomized design. Nutrient solutions were prepared by dilution in water and applied by spraying 10 ml per bed every three days over a four-week period. Environmental conditions such as temperature, humidity and light were maintained consistently. Daily observations recorded yield, contamination and mushroom quality. External supplementation successfully reactivated SMS, extending the productive period by approximately two weeks. The two-weeks average harvest per kilogram of growing media was 17.69 g (Control), 50.56 g (GS 2%), 55.09 g (GS 3%), 67.36 g (GS 4%), 60.30 g (PYD 2%), 71.37 g (PYD 3%) and 58.95 g (PYD 4%). By comparison, the conventional method yielded an average of 61.87 g over three months. The highest regrowth was observed with 3% PYD, followed by 4% GS. PYD outperformed GS, likely due to its higher nutrient and nitrogen content, although excessive concentrations promoted contamination. Economically, PYD was also cost-effective than GS. These findings demonstrate a simple, low-cost strategy for small-scale mushroom farmers to enhance substrate efficiency, increase yields, reduce input costs, minimize waste and promote environmentally and economically sustainable cultivation practices.