Traditionally carried out in situ
on mushroom farms in bags,
blocks or trays,
technological developments now enable the preparation of spawn-run compost (Phase III) in bulk tunnels
at composting facilities.
During a 14–18 day incubation period, optimum environmental conditions are: compost temperatures of 25oC, carbon dioxide levels in the range 0.3-1.5% and high (>90%) relative humidity.
To induce A. bisporus fruitbody production, it is essential, to cover the colonised compost with an approximate 5cm layer of relatively inert casing material. Typically, mixtures of sphagnum peat and calcium carbonate are used.
The casing provides water to enable the growth and development of mycelium and fruitbodies and protects the compost from desiccation. During case-run, similar environmental conditions to spawn-running are maintained for c. 7-10 days.
When the mycelia reach the casing surface, reducing both air temperature to 16-18oC and carbon dioxide levels to 600-1000 ppm induces sporophores (“mushrooms”) to form.
Sporophore production occurs in discrete "flushes" or "breaks", commencing 2-3 weeks after casing and continuing at approximately weekly intervals. Typically, three or four flushes are harvested from each crop.
