Modern mushroom cultivation is an indoor, highly-intensive and controlled series of processes aimed at growing fungal cells, and so is very different from green crops. Up to nine crops per year are produced in a growing house. A number of mushroom species are grown in different countries but in the UK the predominant species grown is the cultivated white mushroom Agaricus bisporus; it is marketed in a range of products including white and brown varieties, and closed, open and Portobello types. The UK mushroom industry annually produces around 70,000 tonnes of mushrooms worth £113M, the largest value of any protected crop. The annual world value of A. bisporus is $4.7 bn.
The first stage of mushroom cultivation is the production of the substrate, mushroom compost, from which it gains nutrition. Wheat straw is mixed with a nitrogen source, gypsum and water, and the ensuing microbial fermentation under controlled conditions results in mushroom compost containing partially decomposed straw embedded in humic substances. The compost is inoculated with Agaricus bisporus mycelium which fully colonises the compost after approximately 17 days. The final stage of mushroom cultivation is the manipulation of the environment to stimulate mushroom fruitbody production; the colonised compost is covered with a 55 mm layer casing soil consisting of a peat/sugarbeet lime mix, the growing room temperature is reduced and gases released during fermentation are diluted by the ventilation with fresh air.
EMR are researching all aspects of mushroom cultivation: compost production and quality, mycelial growth, replacement of peat with alternatives, the stimulation of mushroom production, genomics and mushroom diseases. These approaches have led to a number of research and development opportunities that can be applied to other horticultural crops such as disease suppressive composts, peat replacement, and formulation of growing media.