factors that can influence the moment of cool down and therefore pinheading can differ in each cropping cycle. This explains why creating uniformity during the entire process is vital. Once cool down has been started, growers can be faced by many other factors that can influence pinheading to a lesser or greater extent. First of all, having optimal climate control on the farm is very important. All farms vary widely, so comparing one farm with another is very difficult - even if they seem similar. The specifications of a growing room greatly influence whether uniform air circulation is optimal or sub-optimal. On a tray-growing farm where the trays are packed close together, air will have to be circulated at a much higher speed. This dries out the casing soil more which can easily lead to too many pinheads being formed, which will then develop into too many mushrooms. Air handling in growing rooms is a highly technical specialism, and knowledge and expertise can only contribute to perfectioning this art. Growers are strongly advised to have their farms inspected and measured by air handling specialists if they start experiencing inexplicable problems during cultivation. The speed of cool down - more specifically the speed at which the air temperature is reduced - also significantly influences the number of pins. The air temperature has the greatest influence on the number of pinheads and lowering the CO2


has


the biggest influence on the decrease in compost temperature, as lowering the CO2


relates to


more fresh air – which in general will encourage higher evaporation levels. Evaporation means that heat is expelled from the compost thus causing the compost temperature to drop. Note


that U1-related varieties that form pinheads less spontaneously are more sensitive to changes in CO2


, while U3-related varieties that pin more spontaneously are more sensitive to changes in the air temperature in regard to the number of pinheads produced. During cool down, mycelium gradually starts to contract and form pins (so-called primordia). In principle, the pins formed first should immediately start to grow to stimulate spread. This must be encouraged by the right evaporation levels. If too little, or no, evaporation takes place the pins will stay damp for too long and will start to build up internal moisture, which can lead to bacterial blotch and a short to extremely short shelf life. This type of pinhead turns into poor quality mushrooms that are highly susceptible to discoloration during and immediately post-harvest. Cut stumps usually discolour straight after they have been cut. So, growers must ensure they avoid this situation at all times by making certain the evaporation process proceeds naturally and optimally. In a crop like this, very high number sof mushrooms with scaling may be seen if a high fan speed is used. Poor evaporation can also occur despite a high fan position (e.g., with insufficient cooling capacity and/or too little space between the beds, or incorrect distribution of circulation air in the growing room). In this case, the pinheads and mushrooms fill with internal moisture. Osmotic pressure from the compost forces moisture into the pinheads and if there is little or no evaporation, this disrupts the water balance in the mushrooms. A practical guide is the appearance of the pinheads – they must be and stay white as a sign of optimal evaporation. It is also essential to avoid any


The pinheading process requires a great deal of care, attention and skill.





Growers need good quality compost in order to steer pinheading optimally.


The number of pins that develop to create a second fl ush greatly depends on aspects such as the compost quality.


MUSHROOM BUSINESS 9


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48