At the end of phase i substrate preparation the

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Unformatted text preview: se I, the substrate is bulky and yellow. At the end of Phase I substrate preparation, the substrate should be dense, chocolate brown in color, and have a strong odor of ammonia. The substrate still has some structure so aeration can be maintained during Phase II composting. The potential fresh mushroom yield depends on the amount of dry weight filled. In order to achieve a substrate density in the growing structure necessary to support an economical mushroom yield, the substrate at fill has to be short or dense enough to attain a high substrate dry weight. 5 Figure 5. A tunnel used for Phase II and/or Phase III (spawn-growing) systems. Growing Systems (Phase II) Once Phase I is complete, the substrate will be filled into a system for Phase II substrate preparation and to grow the mushrooms. Phase II takes place in one of three main types of mushroom-growing systems, depending on the type of production system used. The difference in the mushroom-growing systems is the container in which the crop is processed and grown. With a multizone system, the substrate is filled into boxes or trays and moved from room to room as shown in Figure 5. Each room has a different heating, ventilating, and airconditioning (HVAC) system designed for a specific stage in crop development. A single-zone system— or bed farm—consists of several large, stacked beds or shelves within a single room (Figure 6). The substrate is filled into these beds after Phase I, and the crop remains in the one room throughout the process. Bulk pasteurization or tunnels are systems where the substrate is filled into “tractortrailer”–type bins (called tunnels) with perforated floors and no covers on top of the compost (Figure 7). Phase II and, occasionally, the next phase of growing are carried out within these tunnels. The substrate may then be filled into a tray, shelf, or even plastic garbage bags for the remaining part of the process (Figure 8). 6 Figure 6. Single-zone, bed, or shelved farm. These shelves are aluminum; many farms have wooden bed boards. Figure 7. Trays used for a multizone system, moving through a tray-filling line. Phase II: Finishing the Compost Phase II composting is the second step of compost substrate preparation. The first objective of Phase II is to pasteurize the composted substrate. The composted substrate is pasteurized to reduce or eliminate the bad microbes such as insects, other fungi, and bacteria. This is not a complete sterilization but a selective killing of pests that will compete for food or directly attack the mushroom. At the same time, this process minimizes the loss of good microbes. Figure 8. Bag-growing system often uses substrate prepared in a bulk composting facilities. The second goal of Phase II is to complete the composting process. Completing the composting process means eliminating all remaining simple soluble sugars and gaseous and soluble ammonia created during Phase I composting. Since ammonia is toxic to the mushroom mycelium, it must be converted to food the mushroom can use. The good microbes in Phase II convert toxic ammonia in solution and amine (other readily available nitrogen compounds) substances into protein—specific food for the mushroom. At the end of Phase II, volatile ammonia (concentration more than 0.05 percent) will inhibit mushroom spawn growth. Generally, ammonia concentrations above 0.10 percent can be easily detected by a person and are toxic to the spawn. Most of this conversion of ammonia and carbohydrates is accomplished by the growth of the microbes in the compost. These microbes are very efficient in using Phase I composting products, such as ammonia, as one of their main sources of food. The ammonia is incorporated as mostly protein into their bodies or cells. Eventually the mushroom uses these packets of nutrients as food. 7 Phase II objectives are possibly the most difficult procedures in growing mushrooms. Because of a composting or other cultural problem, growers sometimes have to adjust Phase II programs. The Phase II process takes anywhere from 7 to 18 days, depending on how the air and compost temperatures are managed to control microbial activity. During Phase II in standard bed or tray systems, compost temperatures are brought down through all temperature ranges to ensure that all the different species have a chance to...
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This document was uploaded on 03/16/2014.

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