There are various types of substrates which are used in mushroom growing, including:

• Mushroom compost, which is sterilised (unused and pasteurised)
• Horse manure, which is straw-rich
• Saturated straw
• Spent mushroom compost and old straw
• Logs and stumps
• Sawdust, especially poplar sawdust; this is ideal for Agrocybe cylindracea
• Bundles of twigs 20 to 30 cm thick which are well moistened
• Chopped straw and sawdust; this is particularly good for Lepista nuda
• Wood chips (70%) and rice bran (30%); suitable for Flammulina velutipes
• Pasteurised straw, sawdust and barley chaff to a pH of 5.5
• Straw (30%), wood chips (60%) and soybean meal (10%); this is ideal for Lentinus edodes
• Burnt ground during the late winter/early spring stimulates morels to fruit

Thanks to Clifford Davy of Forest Foragers.