Most by-products from agriculture and forestry industries can make up a base medium for mushroom culture. This base medium is commonly referred to as the"fruiting substrate".This primary material is often supplemented with a carbohydrate- and protein-rich additive to enhance yields. Here is a short list of the materials that can be recycled into mushroom production Wood wastes, paper products
Cereal straws & grain hulls Corncobs
Coffee plants & waste Tea leaves Sugar cane bagasse Banana fronds
Seed hulls (cottonseed and oil-rich seeds)
Hulls of almonds, walnuts, sunflower, pecans, and peanuts Soybean meal, roughage (Okara) &
soy waste Artichoke waste
Cactus waste: saguaro & prickly pear, yucca, agave*
A vast variety of woods can be used for growing gourmet and medicinal mushrooms. Generally speaking, the hardwoods are more useful than the softwoods. Several wood types may not perform by themselves, but when combined with more suitable woods—and boosted with a nutritional supplement—will give rise to commercially viable crops. Recommended hardwoods are alders, birches, horabeans, chestnuts, chinkapins, beeches, ashes, larches, sweetgums. tanoaks, cottonwoods, willows, ironwoods, walnuts, elms, and similar woods. Suggested softwoods are Douglas firs and hem locks. Most other pines (ponderosa, lodgepole), cedars, and redwooa are not easily degraded by mushroom mycelium. Aromatic hardwoods, such as eucalyptus, are not recommended un^ til we better understand why some people become ill from eating otherwise edible mush* An Oyster mushroom, Pleurotus opuntiae, is native to prickly pear, agave and yucca. Although I have not cultivated Oyster mushrooms on these cacti, they shoüld serve well as a substrate base.
rooms growing from this source. (Arora, 1990.) Cedars and redwoods are likewise not recommended as they decompose slowly due to their anti-rotting compounds. Obviously, these same compounds stifle the growth of mushroom mycelium.
Other woods than those listed may prove to be satisfactory. Hence, experimentation is strongly encouraged I find that the fast-growing, rapidly decomposing hardwoods are generally the best because they have greater ratios of starch-enriched sapwood to heartwood. These sugars encourage rapid initial growth, resulting in full colonization in a short period of time. The key to successful cultivation is to match the skills of the cultivator with the right strain on the proper substrate under ideal environmental conditions.
For outdoor log culture, disease-free logs should be selected from the forest in the winter or early spring. If you use sawdust and chips for indoor or outdoor cultivation, freshness counts—or else competitors may have already taken hold. Lumber mills, pulp mills, furniture manufacturers, and many other wood product-companies generate waste usable to the mushroom cultivator. However, those industries which run mixed woods and do not separate their sawdust into identifiable piles, are not recommended as substrate suppliers. Cultivators face enough problems in their struggle to understand the different yields of each crop cycle. Hence, mixed wood sources are best avoided, if possible.
Red alder (Alnus rubra) is a "weed tree" in western Washington State of North America. Like poplars and cottonwoods, its penchant for valleys, wetlands and open habitats encourages a prodigious growth rate. Many of these trees are common along roads where they foul telephone and electrical lines.A whole industry has arisen dedicated to rendering these trees into chips, a fortuitous situation for mushroom cultivators. A matrix of smaller and larger particles can be combined to create an ideal habitat for mycelium. The smaller particles stimulate quick growth ("leap-off'). The larger particles encourage the mycelium to form thick, cordlike strands, called rhizomorphs, which forcibly penetrate through and between the cells.The larger chips become nutritional bases, fruiting platforms, giving rise to super-large mushrooms.This concepthas been an overriding influence, steering my methods, and has resulted, for instance, in the large 5 lb. specimens of Stropharia rugoso-annulata, the Garden Giant, that is pictured in this book. A simple 50:50 mixture (by volume) of sawdust and chips, of vary ing particle sizes, provides the best structure for the mushroom habitat. The substrate matrix concept will be explored in greater detail later on.
Cultivators should avoid wood chips originating from trees along busy roadways. Automobile exhaust and leachate from the oil-based asphalt contaminate the surrounding soil with toxins, including lead and aluminum. Metals can be concentrated by the mushroom mycelium and transferred to the mushrooms. Wood chips from county roads with little traffic are less prone to this heavy metal contamination.This problem is largely circumvented by obtaining sawdust and chips from larger diameter trees. Sawmills and pulp chip companies provide the cleanest source of wood debris for substrate preparation.
Currently, the heavy metal concentrations taken up by mushrooms are well below the stan dards set by the United States government for fish, for instance. However, air pollution is a growing concern. My analyses of mushrooms grown in China, California, and Washington state revealed that the Chinese mushrooms had the greatest aluminum, mercury & lead concentrations, with Californian mushrooms next, and mushrooms grown in the less industrialized Olympic Peninsula ofWashington had the least. With the phasing out of lead-based gasoline and the implementation of tougher environmental restrictions, pollution of wood sources maybe ameliorated. (For more information on the concentration of metals and toxins, and their potential significance, consult Stijve, 1992 &
Mushroom News, Dec., 1992). Many environmental service companies will analyze your product for a nominal fee, usually between $ 50-125 U. S. If an analysis shows unusually high levels, the same specimens should be sent to an unrelated laboratory for confirmation. Please consult your Department ofAgriculture, county extension agent or comparable agency for any applicable threshold requirements.
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