Production of the edible mushroom in the United States totaled 802 million pounds during the 2007–08 growing season, with 521 million pounds or 65% produced in Pennsylvania (Norris, 2009). The major ingredients in mushroom-growing substrate from farms in Pennsylvania are typically recycled agricultural waste products and other materials, which include hay, straw and horse bedding, poultry litter, corn cobs, corn stover, cottonseed meal, cocoa hulls, and gypsum in various amounts and proportions (Chang and Miles, 1989; Stamets, 2000). The ingredients are mixed, blended, and irrigated thoroughly, placed inside a production facility, and pasteurized with steam heat to sterilize the substrate before inoculation with mushroom spawn (Wuest, 1982). Sphagnum peatmoss is added later in the growing process (Beyer, 2003; Chang and Hayes, 1978).
After a cropping cycle has been completed and the substrate has been depleted of nutrients needed for growing mushrooms, the substrate is removed from the production facility and the discarded material is then referred to as fresh mushroom compost (Beyer, 2003; Chang and Hayes, 1978; Wuest, 1982). Before removal, however, the substrate is again pasteurized with steam heat to eliminate the potential for unwanted fungi and weed seeds (Wuest, 1982). Fresh mushroom compost was previously called spent mushroom substrate or mislabeled as “mushroom soil” (American Mushroom Institute, unpublished data). Although weathered or outdoor-aged mushroom compost has been used as an organic fertilizer and soil amendment for plant production in agriculture and horticulture (Chong et al., 1991b; Lohr et al., 1984a; Maher, 1991, 1994), limited information is available regarding the analysis of fresh mushroom compost (American Mushroom Institute, unpublished data). An estimated 650,000 to 700,000 yard3 of fresh mushroom compost are generated annually by the mushroom industry in Pennsylvania (American Mushroom Institute, unpublished data; Fidanza and Davis, 2009). The objective of this project was to analyze the fresh mushroom compost produced in southeastern Pennsylvania for chemical and physical properties considered important for plant growth and soil improvement.
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