CULTIVATION TIPS DLV PLANT MUSHROOMS Picking is an art
By Erik Polman, DLV Plant Mushrooms
e.polman@dlvplant.nl
Photos: DLV Plant Mushrooms
On farms that harvest manually, quality is still the trump card played to beat the compe- tition. Quality depends on many factors. The right quality and quantity of compost, sup- plements and casing soil and good climate control are indispensible. Many companies do have the right blend of skills to be able to produce good mushrooms for the consumer market, but the punnets of fresh mushrooms on the pallet fluctuate in quality. Pickers frequently work under high pressure to harvest a large number of kilos per hour, which in many cases is detrimental to the quality of the mushrooms. Fingernail dents, pressure and impact bruises and badly cut stems all cause quality levels to plummet. Some companies perform quality inspections of the harvested produce on day one, three and five after harvesting. The pickers then assess the quality of a number of punnets to- gether. Strikingly, mushrooms of identical quality will show a wide diversity of keepablity qualities after a few days. Taking good care of the mushrooms post-harvest is essential. The conclusion during these brief evaluation sessions is that a good quality product sells itself! (see photo) So when appraising your pickers don’t just take picking performance into account, but also the picking technique. The appearance of the bed after it has been picked is also important here. Make sure that mushrooms still on the bed are undamaged and that any loose mushrooms have been removed. Then it really is worthwhile growing to showcase quality. Y
ou can never have too much quality… Moisture deficit explained
By Jan Gielen, DLV Plant Mushrooms Manager / Specialist Climate & Energy
j.gielen@
dlvplant.nl
In 2002, moisture deficit was developed on the initiative, and with the contribution, of Cpoint (now DLV Plant Mushrooms). The guiding principle was to create a more stable moisture absorption capacity of the growing room air, and to control growth using less energy than conventional RH-based control. Despite the moisture deficit control feature being widely available as a program update since 2006, and its use by a large number of growers, there is still a lot of uncertainty surrounding its exact meaning. It is often thought that moisture deficit control regulates evaporation. However, this is not – entirely- the case. As our previous tip explained, the entire evaporation process consists of three stages: moisture transport to the mushrooms, moisture absorption by the growing room air and moisture extraction from the room. What the moisture deficit control regulates is the moisture absorption by the growing room air (step 2), and not evaporation as a whole. The essential difference between control based on moisture deficit or RH, is that with conventional RH control the moisture absorption capacity of the growing room air is not just dependant on the RH, but also on the temperature. A more stable moisture absorption capacity of the growing room air can then only be achieved if both the RH and the tem- perature control are extremely stable. This is often not the case in practice, meaning that the moisture absorption capacity of the growing room air- in other words, the moisture deficit – is also unstable. To create a stable moisture absorption capacity of the room air, the RH should always also be adjusted if (large) adjustments are made to the temperature, to keep the moisture deficit constant. If control is directly moisture deficit-based this happens automatically; if the temperature is adjusted, the RH adjusts as well in order to maintain the same moisture deficit. This means that the mutual influence is decoupled and the tempe- rature can be controlled independently to steer the speed of growth, while the moisture deficit control regulates the moisture absorption capacity of the room air.
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