Throughout the period following casing water must be

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Unformatted text preview: ures until flushing be held at spawngrowing temperatures. After flushing, compost temperatures are lowered and air temperature becomes the primary control point. Throughout the period following casing, water must be applied intermittently to raise the moisture level to field capacity before the mushroom pins form. Watering or Irrigation The moisture content of the casing often determines the uniformity of the casing depth. Casing, both by equipment and by hand, becomes more difficult as the casing material increases in moisture (Figure 15). Peat moss casing will lump up or adhere to the different parts of the equipment, making the flow of the material uneven. Knowing when, how, and how much water to apply to casing is an art form that readily separates experienced growers from beginners. Watering the crop is the most delicate operation in mushroom growing. Although each grower may have his or her own preference, no specific casing-management practice and casing material are universally accepted. Despite so much diversity, many growers are still able to harvest good crops with good freshmarket quality. Figure 14. Difference in time when CAC or CI is added to the casing. The two figures on the left and the two on the right show the difference in spawn growth over time into the casing. Mycelium 3 days 3 days Casting 11 days Not CAC’d 12 Compost 5-7 days CAC’d Although much has been written about when and how much water to apply at certain stages in the crop’s development, most growers rely on their ability to “read” the crop and determine how the mushrooms look from day to day. Water constantly moves throughout the cropping period: water is lost through evaporation and transpiration, and the mushroom takes up water into its cells; water is replaced when watering the casing layer. The increase in the weight of the mushroom from pinning to maturing is related to the rapid uptake of water from the casing and compost. The mushroom doubles in size 2 days before harvest, putting more strain on the pipe system in the compost and casing. As the mushroom matures during a flush, its weight gain is attributed to the accumulation of nutrients and water from the substrate. Figure 15. Most watering is done by hand, although newer farms use hand-propelled watering trees. Pinning Mushroom initials develop after rhizomorphs have formed in the casing. The initials are extremely small but can be seen as clumps on a rhizomorph. As these structures grow and expand, they are called primordia or pins (Figure 16). Mushroom pins continue to grow larger through a prebutton stage and ultimately enlarge to mature mushrooms. Mushroom harvesting begins 15–21 days after casing, which is normally 10–12 days after flushing and 7–8 weeks after composting started. The cultural practices used during pin development and cropping include the management of air and compost temperatures and CO2 content of room air, and is often dependent on the strain and number of pins the grower wishes to form and develop. Figure 16. The developmental stages of the fruiting process. Mycelium Initials—Clumping Pin—Primordia Pea-Sized Pin Pre-Button 13 Air-handling systems regulate the amount of fresh air entering the room and temperatures within the room. Ventilation requirements depend on the amount of mushrooms to be grown on the beds, heat, and CO2 production, which increases with temperature. Uniform air movement and circulation is important to prevent stale air with high CO2 levels from building up around the mushrooms, which lowers fresh quality. Air temperature is maintained in a range of 60–66ºF (15–17ºC); CO2 levels range from 1,000 to 2,500 ppm (1– 2.5 percent) during the pinning and cropping stages. The most critical stage of the mushroom’s development for fresh quality and yield improvement is during the Rapidly Expanding Stage (RES), when the mushroom doubles in size every 24 hours (Figure 17). This expansion stage depends on temperature, moisture of the compost, and casing. The environment inside a production room determines the rate of transpiration, which aids in the flow of nutrients and moisture into the mushrooms. Mushroom size is dependent on the number of pins that develop for a break or flush and by how the crop is prepared and managed. Portabella mushroom growers have learn...
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