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Unformatted text preview: he bag or bottle. During the process, temperatures are maintained at 74–76ºF (23–24ºC). Uniformity of the air circulating around the bags is important to ensure that all containers are kept within the desired temperature range. Mycelium is sensitive and its fruiting mechanism can be easily damaged at high temperatures. Figure 11. Spawn grains used to seed the compost with mushroom mycelia. Spawn is cooked, sterilized, grain cooled, and inoculated with mushroom mycelia. There is no in vitro test to determine a stock culture’s validity. A series of cropping trials must be conducted on the mycelial stock culture to determine a culture line’s value. Mushroom yield, size, color, cap shape, and any other desired quality or growth factors are selected and then compared for each culture line. 9 Spawning On bed farms, spawn and supplement are broadcast over the surface of the substrate. Uniformity of this distribution is critical to achieve even spawn growth and temperatures. On tray or bulk farms, spawn is usually metered into the substrate during the mixing operation. Spawning is the cleanest operation performed on a mushroom farm. All equipment, baskets, tools, and so forth should be thoroughly cleaned and disinfected before spawning. The amount of spawn used depends on the length of the spawn-growing period and compost fill weights. The use of more spawn will result in a quicker colonization and more efficient use of substrate nutrients. Improved colonization of substrate will help ensure that the mushroom mycelia will grow quicker than other fungal competitors. During the spawn-growing period, heat is generated and supplemental cooling is required. Substrate tempera- tures should be maintained at 75– 77ºF and relative humidity should be high to minimize drying of the substrate surface. Under proper conditions, the spawn will grow as a delicate network of mycelia throughout the substrate. The mycelium grows in all directions from a spawn grain. Eventually mycelia from different spawn grains fuse together, making a spawned bed appear as a white root-like network throughout the compost (Figure 12). As the spawn grows, it generates heat. If the compost temperature increases to above 80° or 85°F, depending on the cultivar, the heat may kill or damage the mycelia, reducing crop yield and/ or mushroom quality. The time needed for spawn to colonize the compost depends on the spawning rate and its distribution, the compost moisture and temperature, and the nature or quality of the compost. A complete spawn run usually requires 14 to 21 days. The spawn-growing period is considered complete when spawn has completely colonized the substrate and the metabolic heat surge is subsiding. Figure 12. Handful of mushroom substrate showing fully colonized spawn growth. 10 Substrate Supplementation The compost has to provide the mushroom mycelium with a smorgasbord of food. Not only is ligninhumus complex and cellulose important, but protein, fat, and oils are also important. A good analogy is protein serves as the mushroom’s “steak,” carbohydrates its “potatoes,” and lipids (fats and oils) its “butter.” Like people, mushrooms should eat a balance of all these food types. The main source of “steak and butter” for the mushroom is from Phase II microbes. The dead cells of thermophilic fungi, bacteria, and actinomycetes “firefang” are the packages that deliver protein and fat to the mushroom (Figure 9). The addition of delayed-release supplements further enhances the protein and lipid content of the compost for the mushroom. Many of these supplements consist of a high-protein oil material, such as soybean meal, cornmeal, or feather meal, that has been treated to delay the availability of the nutrient for the mushroom. If an untreated supplement is added to the compost at this time, it often becomes a “candy bar” to other microbes, weeds, or competitor molds. These molds grow more rapidly than the mushroom mycelium and can quickly colonize the compost, competing with the mushroom for nutrients. The oils or lipids in these supplements are used by the mushroom to...
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This document was uploaded on 03/16/2014.

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