COMPOST 4
should be mixed once, or more, so that any cold zones also have the chance to reach 80 degrees.
Pasteurisation and conditioning Pasteurisation Pasteurisation is actually the selection of micro-orga- nisms and is a process that walks a fine line between good and bad. Competitors should be destroyed or weakened, while beneficial micro-organisms should be left unharmed. Effective pasteurisation depends on the temperature, duration and ammonia concentration. The importance of a sufficiently high ammonia concentration is often underestimated. With too low ammonia concentrations, pasteurisation is not effective enough, but this can be partly compensated for by a longer pasteurisation time. Vice versa, with a too high ammonia concentration, you should reduce the duration otherwise too many useful microflora will be removed. Conditioning During conditioning, the optimal compost temperature is applied to stimulate the growth of specific microflora which are converted into a suitable nutrient medium for mushroom mycelium in phase I. Micro-organisms flourish that decompose organic matter and ammonia and convert these substances into suitable nutrients; mould develops which will stimulate mushroom mycelium growth at a later stage, and actinomycetes are also present that produce antibiotics. The temperature in the lower layer of compost in the tunnel must be maintained at a high enough level, preferably above 42 degrees Celsius. If not, mesophilic moulds will be able to develop too strongly, which will cause problems later on the cultivation process.
Inoculation
It is very important that at the end of the conditioning stage, before cooling, the compost is entirely ammo- nia-free. Even a very low ammonia concentration can inhibit growth, or even destroy mushroom mycelium. Moulds that are less sensitive to ammonia will quickly step in and dominate. The compost temperature is lowered to 25 degrees, so that microflora which performed useful tasks during conditioning are deactivated.
The selective nutrient medium is now virtually ready. This is the most sensitive time for infection as nothing is actually growing in the compost at this stage, and anything that does start to grow has free rein to multi- ply unhindered.
Composing plants that supply incubated compost must observe stringent hygiene standards. A flow of infection from incubated compost or, even worse, from a farm, can have disastrous consequences. During inoculation the hall is a clean room. Machines
36 MUSHROOM BUSINESS
The source of plaster mould is often compact, recycled compost. In inoculated compost this mould can cause serious problems.
and the hall itself have been meticulously disinfected, filtered air is used to introduce over pressure in the space, and all the personnel should wear clean clothing and footwear. During inoculation, a very large dose of mushroom mycelium is mixed through the compost to elicit the fastest possible colonisation. The more spawn is used and the more inoculation points, the faster the compost will be colonised by the mycelium and the less suscep- tible it will be to infection. The right volume of spawn greatly depends on the conditions at the company. With perfect hygiene and good compost considerably less spawn can be used than in more unfavourable condi- tions.
Incubation
The primary conditions required for mycelium to start colonising the compost right from the carrier grain are ammonia-free compost with a sufficiently low pH and a good moisture content.
Compost can be incubated in the form of blocks, in beds, trays or in tunnels. Each system has its own particular parameters. However, some rules of thumb are univer- sal: mycelium hates high air speeds and dry air; there must be enough oxygen in the compost and the optimal compost temperature is around 25 degrees Celsius. If you stray too far from these optimal conditions, other moulds will seize the opportunity. Never forget there is always a low concentration of other moulds lying in wait in the compost, and if conditions become only slightly less favourable for mushroom mycelium, they turn in favour of this other group. Temperature
At too high temperatures, the speed of growth of mushroom mycelium will slacken and growth of other
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