PINHEADING
Too many or too few pinheads
Achieving the correct amount of pinheads during pin setting is probably the most challenging process that growers have to steer in mushroom growing. There are no ready-made solutions in the form of computer programs that can effortlessly determine the right number of pinheads, as too many natural influences have a bearing on the outcome. However,
there are a number of practical guidelines that growers can keep in mind. By Jos Buth,
josbuth@gmail.com
T
he first question is defining your intended market – are you culti- vating for the fresh market or the processing sector? Both markets
require certain grades, and the fresh market also specifically entails looking at the harvesting capacity, which can increase considerably when growing easy to pick mushrooms. The number of pinheads formed, and the actual moment they develop into mushrooms, has an immense effect on the harvesting capacity, but above all, on quality. At some time or other, growers all over the world will be faced by too many mushrooms per square metre or even over-pinning, but also experience cropping cycles with too few developed mushrooms, with all the resulting consequences.
What determines pinheading? Firstly, compost has a huge impact on pinhead- ing. The quality, amount and activity of the compost greatly affect pin formation in the first, second and third flush, and whether these pins subsequently grow into mature mushrooms. Another influential factor is the addition or not of supplements, and if so, in which quantity – in other words, how many easily decomposable nutrients are available for the mushrooms. In addition, the quality of the casing soil (structure and moisture content) also determines the num- ber and size of the pinheads, as does the climate and technical specifications of the growing room. Is there enough bacteria (Pseudomonas Putida, which is usually found in every type of casing soil, provided it has not been too strongly disinfected or not steamed as a disinfection measure) present to enable good pinheading?
8 MUSHROOM BUSINESS
And, not to forget, factors such as the casing soil pH and the how high the mycelium develops in the surface of the casing soil. In short, there are countless components that can affect pinhead- ing in each successive cycle, and present a great challenge to the skills of growers, even more so as they have very little influence at all on many of them (natural influences on the raw materials that comprise the compost and casing soil, for example).
Skill
The entire pinheading process is highly complex and tests the skill and expertise of growers to take the right decisions at the right time. In principle, pinheading starts at the moment of cool down. This is when the process starts of gradually changing the nature of growth from vegetative (mycelium growth) to generative (pinheading). On Dutch mechanical harvesting farms, the moment of cool down determines the precise moment (to the hour) of mechanical harvesting. This says a lot about the precision and accuracy of the process, and that taking such decisions correctly requires a great deal of care, attention and skill. The speed at which casing soil is colonised by the mycelium governs the moment of cool down in particular. Just how fast the mycelium colonises the casing is determined in turn by factors including the compost quality, compost pH (mycelium grows faster in the casing soil in phase III compost with a pH value below 6.5 than in compost with a value above 6.5), use of CAC compost or CI in the casing soil, casing soil quality, amount of water, the point in time of the last spraying session before cool down, CO2
and temperature. There are multiple
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