Internet Naturalist – August 17, 2014

  • Mushroom Compost
    Mushroom compost (also referred to as “spent mushroom substrate” or “mushroom soil”) has become a popular organic soil amendment for the establishment and maintenance of lawns and sports fields, gardens, agricultural and horticultural crops and with land reclamation projects. Here are some commonly asked questions and answers about mushroom compost. | The visual appearance of a good quality, thoroughly processed mushroom compost typically resembles a dark topsoil, has a loose crumbly structure, and has an “earthy” aroma. Recent research conducted at the Pennsylvania State University showed that mushroom compost contains an average of 25 percent organic matter and 58 percent moisture on a wet volume basis. Where uniform application and good mixing with soil is required, this amount of organic matter and moisture in mushroom compost is ideal for handling and making surface applications or incorporating into the soil. Mushroom compost contains an average of 1.12 percent nitrogen in a mostly organic form that slowly is available to plants. Also, mushroom compost contains an average of 0.67 percent phosphate (phosphorous) and 1.24 percent potash (potassium), as well as other plant nutrients such as calcium (2.29 percent) magnesium (0.35 percent) and iron (1.07 percent). The average pH of mushroom compost is 6.6 (6.0 to 7.0 is an ideal range for most plants). The amount of carbon relative to nitrogen is an important indicator of nitrogen availability for plant growth, and an ideal compost should have a ratio of 30:1 or lower. Mushroom compost has an excellent 13:1 ratio, indicating outstanding nutrient availability and mature and stable organic compost.
  • Mushroom compost–use carefully | Oregon State University Extension Service | Gardening
    Commercial mushroom growers in the Willamette Valley grow tons of mushrooms in an elaborate mixture that gardeners love – mushroom compost. Often sold at landscape supply houses, mushroom compost can help amend garden soil, but should be used with caution, according to John Hart, soil scientist with the Oregon State University Extension Service. Mushroom compost is rich in soluble salts and other nutrients and can kill germinating seeds and harm salt-sensitive plants including rhododendrons and azaleas. | The recipe for mushroom compost varies from company to company, but can include composted wheat or rye straw, peat moss, used horse bedding straw, chicken manure, cottonseed or canola meal, grape crushings from wineries, soybean meal, potash, gypsum, urea, ammonium nitrate and lime. | "Each mushroom growing facility has its own recipe," explained John Stout, general manager of PictSweet Mushrooms in Salem. "It’s very precise. The compost ingredients are weighed out, then mixed
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