Proper mushroom compost is essential for the cultivation of edible or medicinal mushrooms. Although, according to the American Mushroom Institute, mushrooms are one of the most difficult commodities to grow, a diligent mushroom farmer can make his or her own mushroom compost that will ensure a healthy mushroom harvest. Sterilization and pasteurization are the most essential components in making a quality mushroom compost as the risk of contamination is the number one threat to a quality mushroom crop.
To make a vegetable based compost, mix hay, straw, crushed corncobs and gypsum. To make a manure based compost, mix manure and gypsum.
Put your compost base into a compost heap or compost bin and leave under the sun for two or three weeks to allow it to decompose thoroughly. Cover the compost heap or bin with a tarp or plastic to help heat up the compost and facilitate the decomposition of the organic materials.
Steam pasteurize the compost indoors. Use a sterilized room that has vents that allow steam to be blown in and heat up the room to at least 160 degrees. You must kill all pests that may be living on the compost or the mushrooms will not grow.
Place the pasteurized compost in trays and mix in whatever mushroom spawn you are using. Totally cover the tops of the trays with peat moss.
Keep the mushroom compost indoors and control the temperatures and humidity. If there has been no contamination, mushrooms should begin to grow within a month.