At the PictSweet mushroom farm, huge piles of mushroom compost sit for about 30 days and do what compost does - heat up. The straw provides the structure and some food for bacteria, and the urea, cottonseed meal and chicken manure provide most of the nutrients. The bacteria multiply, forcing the temperature inside the pile up to more than 160 degrees F, killing any weed seeds or pathogens that might have been present in the straw or animal wastes. The result is mushroom compost, ready to grow a crop of commercial table mushrooms. The cured compost is placed in beds in a dark, cool and humid warehouse and then is pasteurized at about 140 degrees F to kill any surface disease-causing organisms and pests, said Stout.
Workers then inoculate the compost with mushroom spores.
Underground roots called mycelium grow in the compost, then five weeks after inoculation, mushrooms are ready to pick. A crop continues to be harvested for three to four weeks before the bed is exhausted, said Stout. Mushroom compost can supply nutrients and increase the water-holding capacity of the soil. But mushroom compost can be too much of a good thing for seeds, seedlings and young plants, said OSU's Hart. To avoid killing germinating seeds and stressing heath family members, Hart recommends mixing mushroom compost with garden soil before using it on young plants.