Gabrielle Young

Current mushroom (Agaricus bisporus) cultivation practices use peat, an environmentally costly resource. Peat functions as a water reservoir, supporting mycelial growth and mushroom formation. There is a knowledge gap in characterizing the physical attributes of alternative materials; conventional methods are destructive and often imprecise. This research aimed to determine, over time, the physical properties of peat and two bark-based alternative casing materials using X-ray computed tomography as a novel, high-resolution approach. A microcosm culturing technique was developed to facilitate scanning. A series of scans was taken at key growth stages to assess the dynamic changes that occur within the casing over the course of a mushroom production cycle. Measurements of porosity, pore surface area and pore size distribution revealed significant differences between peat and bark-based alternatives in addition to capturing the changes within each casing material over the mushroom production life cycle. Peat was found to have greater average pore size than bark-based treatments, and this divergence in pore size distribution increased significantly between treatments over the time frame of the experiment. A significant finding of the research is that relative increases in the air-filled porosity of different casing materials may be a useful predictor of casing media performance.

White button mushrooms are an important crop globally, and due to the role of peat in current cultivation practices, the industry is under increasing pressure to find suitable alternatives. Peat functions as “casing”, a surface layer that, amongst other functions, provides available water to the fungal mycelium and is considered essential for mushroom growth. This research aimed to determine the potential of bark as an alternative casing material and its suitability for commercial mushroom production. Two experiments were conducted, comparing two types of commercially available peat casing with bark-based casings. The bark casing in Experiment A was found to be statistically similar to the peat casing in terms of yield and quality. The two bark casings in Experiment B failed to produce a 1st flush of mushrooms, and total yields were significantly lower compared to the peat casings, highlighting the fact that the consistency of the bark material across both experiments was variable. There were several issues associated with the bark casing, which included water stress and cropping delays, all of which would be unacceptable from a commercial perspective. Further research is required to refine bark-based casing, focusing on a better consistency of the bark feedstock and reduction of contamination risk. This work contributes to ongoing research and development to address the dependency of mushroom production on peat.