CULTIVATION TIPS DLV PLANT MUSHROOMS White mushrooms sell themselves!


By Erik Polman, DLV Plant Mushrooms e.polman@dlvplant.nl


Finding less than perfectly white mushrooms on the supermarket shelves can have many rea- sons; raw materials, cultivation method, climate, picking technique, care and transport. At farm level, mushrooms indicate whether they are ‘happy’ and grown under ideal conditions. Bad, or irregular, evaporation is often the culprit behind discolouration. Symptoms include a sticky feel during harvesting, yellow damp patches on the cap and stripes on the stems, hollow stems, bacterial blotch, discolouration of the cut surface in the stem or watery stipe. Reacting well to e.g. day and night climates can result in more uniform evaporation, as well as moisture deficit-based control. The evaporation is usually too low. Using a minimum setting for the fresh air inlets can avoid many problems. However, if the mushrooms are beautifully white during cultivation, it’


s important to check how well the pickers are actually picking. Mushrooms


should be removed from the casing soil by a gentle twist. Hold the mushrooms using the finger tips and do not roll them in your hand from finger to finger otherwise they will be damaged. Despite the use of gloves, damage caused by nail dents is also common. Try saving a couple of punnets per picker and looking at them after one, three and five days. This will reveal any differences in quality and motivate the pickers to improve their technique where necessary


.


Good quality needs no advertisement – certainly if the mushrooms are treated carefully (see photo). It is also very important to cool down mushrooms quickly to 2 - 4 ˚C post-harvest. Ensuring the mushrooms are properly chilled before sealing the packaging or closing lids prevents condensation which subsequently leads to discolouration. Avoid placing them in di- rect sunlight or draughts as this also quickly leads to discolouration, reduced keepability and a product that is less saleable.


Fan characteristics and choice


When selecting the most appropriate fan, considering the air flow the fan has to supply is not the only important point, but also at what resis- tance this air flow should be supplied. A general rule of thumb is an air flow of 22.5 m3/h/m2 growing surface area for manual picking farms (25 m3/h/m2 for mechanical harvesting), at a resistance of 600-650 Pascal. Farms are regularly equipped with incorrectly chosen fans, or in the case of expansion projects the fans left working have insufficient capacities. One of the most common forms of expansion is placing an extra (6th or 7th) bed. This type of addition results in 20 or 16.7% more growing surface, respectively should increase accordingly


37


. This clearly means that the fan capacity . If the fan, the motor and the frequency con-


By Jan Gielen, DLV Plant Mushrooms Manager / Specialist klimaat & energie j.gielen@dlvplant.nl


troller are sufficiently dimensioned, this problem can be simply solved by setting the frequency controller to a higher maximum. For instance, with a 20% increase in surface area, the frequency controller must also be set 20% higher. The previous setting of 50 Hz must now be incre- ased to 60 Hz. In new-build projects the same problem sometimes also occurs, when issues such as cost mean a relatively small fan is chosen. A small fan may just about be capable of delivering the required flow, but it uses more energy than a larger fan. So the savings made at the acquisition stage are cancelled out later by the higher energy consump- tion. To illustrate this, an example is used whereby an air flow of 9000 m3/h (i.e. 2.5 m3/s) at a resistance of 600 Pascal is required. The graphic shows the fan characteristics of the CNA-400 (40 cm diameter) and the CNA-630 (63 cm diameter). Both centrifugal fans can deliver 2.5 m3/s at 600 Pascal. However, to do so the CNA-400 must run at approximately 2000 RPM, causing the fan performance to drop below 50 % while the required power for the motor rises to +/- 3.2 kW


. The CNA-630 only


needs to run at 950 RPM, which means the fan performance remains al- most maximum (72 %) and the required power does not exceed +/- 2,1 kW


%. To arrive at the right dimensions for your fan, remember to include the energy consumption in your calculations.


. The energy saved by using a larger fan in this situation is roughly 35


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