CULTIVATION TIPS DLV PLANT MUSHROOMS Over developed mycelium
By Erik Polman, DLV Plant Mushrooms
e.polman@dlvplant.nl
Photos: DLV Plant Mushrooms
The amount of mycelium wanted on top of the casing soil varies from farm to farm. These differences are influenced by factors including the type of casing soil, the compost qua- lity , the climate control options, and what the grower is aiming to achieve. If a grower is used to letting the mycelium develop quite high up in the casing, there will regularly be periods when it is difficult to keep mycelium development in check. In other words; the mycelium continues to grow vegetatively instead of starting generative growth. There can be a range of causes, which are often difficult to identify. If you experience problems, there are various options for subsequent cropping cycles; Let some air into the room throughout the entire development phase of the mycelium in the casing layer. This will help trigger the transition from vegetative to generative growth and stop excessive vegetative growth. If you have experienced too many pre-pinners with this method, you could also try starting cool down differently. Instead of slowly lowering the temperature from e.g. 20 to 17 ˚C, it’s better to briefly (2-6 hours) lower the temperature to 18 ˚C and then revert to following the original temperature line. At this low temperature the mycelium will easily stop growing, and there will hardy be any effect on the number and spread of the pinheads still to be formed. If the mycelium still keeps growing without any signs of generative growth, you could spray 0.5 to 1 litre / m2. This should halt mycelium growth, but does carry a risk of bacte- rial blotch or other problems with discoloration if the RH is not kept well under control.
Evaporation
By Jan Gielen, DLV Plant Mushrooms Manager / Specialist Climate & Energy
j.gielen@
dlvplant.nl
Every grower knows how important evaporation is, as it is part of their everyday work. The evaporation process is however very complex, and can be affected by various factors. To understand this process better, the evaporation process can be split into three parts: (1) supplying moisture to the mushrooms, (2) moisture absorbed by the growing room air and (3) extracting moisture from the growing room. The supply of moisture to the mushrooms is greatly influenced by compost activity. A more active compost exchanges more heat, and therefore moisture. This is a part of the evaporation process that can only be guided to a limited extent by the grower. The difference between air/compost temperature is the only way to manipulate this. A larger compost/air difference will transport more moisture to the mushrooms, while a smaller compost/air difference will transport less moisture. Moisture absorption in the growing room can be compared with the action of a sponge. Depending on the temperature and RH, the room air has a certain moisture absorption capacity. This is also referred to as the moisture deficit. If the RH remains the same, but the air temperature in the growing room becomes colder (sponge shrinks), the moisture absorption capacity of the room air, or moisture deficit, will decrease. If the RH remains the same, but the air tem- perature in the growing room becomes warmer (sponge swells), the moisture absorption capacity of the room air, or moisture deficit, will increase. So not only the RH, but the combi- nation of the air temperature and RH determine the ultimate moisture absorption capacity, or moisture deficit, of the growing room air. A last, and important, step in the evaporation process is extracting moisture from the growing room. This is determined by the difference between the absolute moisture content (AMC) of the inlet air and the growing room air. Moisture will only be actually extracted if the AMC of the inlet air is lower that the AMC of the air in the growing room. How much air is introduced into the growing room, i.e. the fan position, is obviously also very important here.
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