At a certain stage in the decomposition the mushroom

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Unformatted text preview: f much else. At a certain stage in the decomposition, the mushroom grower stops the process and plants the mushroom so it becomes the dominant organism in that environment. The sequence used to produce this specific substrate for the mushroom is called composting or compost substrate preparation and is divided into two stages, Phase I and Phase II. Each stage has distinct goals or objectives. It is the grower’s responsibility to provide the necessary ingredients and environmental conditions for the chemical and biological processes required to complete these goals. The management of starting ingredients and the proper conditions for composting make growing mushrooms so demanding. Making a Composted Substrate Many agricultural by-products are used to make mushroom substrate. Straw-bedded horse manure and hay or wheat straw are the common bulk ingredients. “Synthetic” composts are those in which the prime ingredient is not straw-bedded horse manure. If bulk ingredients are high in nitrogen, other high-carbohydrate bulk ingredients—such as corncobs, cottonseed hulls, or cocoa bean hulls—are added to the mix. All compost formulas require the addition of nitrogen supplements and gypsum. Additional nitrogen-rich supplements are added to composts to increase the nitrogen content to 1.5–1.7 percent for horse manure or 1.7–1.9 percent for synthetic; both are computed on a dry weight basis. Poultry manure is probably the most common and economical source of nitrogen. A variety of meals or seeds, such as cottonseed meal, soybean meal, or brewer’s grain may also be used. Inorganic or nonprotein nitrogen sources such as ammonia nitrate and urea are also used, but only in small amounts when high-carbohydrate bulk ingredients are used. Gypsum is added to minimize “greasiness” and to buffer the pH of the compost. Gypsum increases the flocculation of colloids in the compost, which prevents the straws from sticking together and inhibiting air penetration. Air, which supplies oxygen to the microbes and chemical reactions, is essential to the composting process. Gypsum may be added early in the composting process, at 70–100 lbs per ton of dry ingredients. A concrete slab, referred to as a wharf, is required for composting (Figure 1). In addition, a compost turner to aerate and water the ingredients and a tractor-loader to move the ingredients to the turner are needed. Water used during a substrate preparation operation can be recycled back into the process. It is, in a sense, a closed system. Water runoff into the environment is nonexistent on a properly managed substrate preparation wharf. Water collected in concrete pits or a sealed lagoon is aerated and recycled to soak bulk ingredients before the composting process begins. Conventional Phase I composting begins by mixing and wetting the ingredients as they are stacked. Most farms have a preconditioning phase in which bulk ingredients and some supplements are watered and stacked in a large pile for several days to soften, making them more receptive to water. This preconditioning time may range from 3 to 15 days. The piles are turned daily or every other day. After this pre-wet stage, the compost is formed into a rectangular pile with tight sides and a loose center. A compost turner is typically used to form this pile. Water is sprayed onto the horse manure or synthetic compost as these materials move through the turner. Nitrogen supplements and gypsum can be spread over the top of the bulk ingredients and are thoroughly mixed by the turner. Figure 1. Traditional compost wharf, showing pre-wet pile on the right and the ricks or windrows on the left. 3 Figure 2 is a close-up of a machine “eating” its way through a compost pile. Once the pile is wetted and formed, aerobic fermentation (composting) commences as microbial growth and reproduction naturally occur in the bulk ingredients. Heat, ammonia, and carbon dioxide (CO2) are released as by-products during this process. Compost activators, other than those mentioned, are not needed. sufficient heat is generated to start the draw of air into the pile. Under anaerobic conditions, organic acids and othe...
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This document was uploaded on 03/16/2014.

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