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CULTIVATION TECHNIQUE
How many pinheads are enough?
During a cultivation cycle, mushroom growers often have to take decisions fast and quickly change their strategy. One of the most challenging periods during cultivation is cool down and pinheading, as this phase determines to a great extent whether you will be harvesting large or small mushrooms, and which quality. The outside climate also plays a significant role here, despite modern, computer controlled climate installations.
By John Peeters
In the first place, every grower has to decide what his precise aims are. If you aim to produce giants you obviously need to take a different approach than if you want to harvest fine grade mushrooms. Growing flats also places a different set of demands, and on mechani- cal harvesting farms you have to have a clearly defined idea of what the best grade is to harvest. There are a number of aspects that are particularly important in steering towards the right number of pinheads. Spawn variety The choice for a certain variety was often the de-
Good spread and good quality. This flush pro- duced 18 kg per square metre with a picking performance of 35 kg per hour, and a maximum cap diameter of 65 mm for the UK market.
termining factor, and growers who wanted to produce large mushrooms often chose a large hybrid variety such as the U1. Remarkably enough a trend has be- come apparent in recent years towards a kind of “one size fits all” intermediate hybrid, with the Sylvan A15 as the most well known exponent. All the other white varieties are compared in one way or another with the A15, but there are actually not any major differences. Amycel, Lambert and other, smaller spawn produces also offer an intermediate hybrid, that doesn’t differ
greatly to the benchmark set by the A15. So selecting a variety has less to do with the choice between large and small, but is rather more about something margi- nally larger or smaller, slightly better keeping qualities, a little higher quality. Every grower has a personal preference - there are plenty of options to choose from. This trend mainly seems to be prompted by production patterns. Intermediate hybrids generally tend to show more consistent production than large hybrids.
Casing soil Looking at casing soil, there are still large differences between what is on offer. Casing soil is what largely determines the outcome of the wish to produce large or small, few or many mushrooms. It is natural that a very coarse casing soil will produce less mycelium, and therefore fewer pinheads, than a casing soil with a fine structure. But one of the most important details in cultivation is how compactly the casing soil is applied. This action is what determines how open the structure of the micro surface of the beds really is. If a growing room with a growing surface of 500 square metres is filled with a casing soil that is heavily compacted, the micro surface will not be much larger than the original 500 square metres. However, if the casing soil is filled loosely onto the beds this same surface area can easily amount to three times or more the original figure. Each thread of mycelium that comes to - or is just below - the surface, is potentially a pinhead. So, levelling very loosely will potentially produce a multitude of pin- heads. If growers experiment until they obtain the ideal situation, a certain line can be established regarding the number of pinheads they can expect to produce. Dutch casing soil is, in principle, coarser and more crumbly than other casing soil, but the current gene- ration of ruffling machines or rufflers on the filling ma- chines make a huge variety of finishes possible, even if the basic material is not always consistent. Obviously it
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