effectively remove 99.9% of the competitor moulds. But 0.1% will survive, and in heavily soiled raw materials with a high concentration of moulds, 0.1% is still too high. Using pure, unsoiled materials is crucial, as in this instance 0.1% is really low. Straw
Straw is surrounded by a waxy layer that offers natural protection against mould growth, so hardly any mould will grow on clean, dry straw.
However, in damp and dirty pressed bales of straw a number of undesirable moulds will develop. The quality of good straw will also deteriorate during the course of storage. Bales on top or underneath the pile are often of clearly inferior quality. Dripping rainwater or melting snow makes the straw in these bales too wet, too fermented, sticky and it will lose structure. Later on this will result in compact lumps of compost in which other moulds will be able to grow. Stacking the bales nine- high instead of four-high results in relatively fewer poor quality bales on top. Even better is covering the pile of straw well, and ensuring sufficient drainage at the base. Horse manure Heavy, old horse manure, mouldy patches, hay and piles of swept up leaves are all potential sources of problems. Horse manure may well be a waste product for stables, but for composter it is the source of what should be good compost. Horse manure should be assessed and selected rigorously, otherwise the final quality will be affected.
The quality of horse manure greatly depends on how much straw is used as bedding, the storage method, how frequently it is collected and the season. Old, heavy horse manure makes the entire batch more heterogene- ous and gives compost with plenty of soft fibres. Young, straw-rich horse manure can be used to make a more homogenous, well-structured compost.
Homogenisation
The basic raw materials such as horse manure, straw, chicken manure, gypsum, and not forgetting water, must be blended together perfectly right at the start so all the materials undergo identical processing condi- tions from the offset.
No matter how well the raw materials are selected, there will always be differences between the various loads. This also necessitates a sufficiently large storage capacity, so that directly adding horse and chicken manure to the production process straight from trans- port is avoided, and the materials are pre-mixed instead to create a uniform batch.
A good mixing installation – consisting of a mixing drum combined with a spinner, for example – should guarantee that the individual raw materials are well- mixed to form a homogenous blend. It is important to avoid leaving any dry patches in the compost. In dry conditions, spores of competitor moulds can easily survive the fermentation temperature of 80 degrees Celsius, while easily accessible carbohydrates will not decompose either in dry patches.
Spores of smokey mould (penicillium hermanssi) can survive the fermentation process in dry patches of compost and reduce yields by some 80% later on.
Fermentation During the fermentation process partial binding of nitrogen into lignin occurs, where later on it can be digested by the mushroom mycelium, but not by competitor moulds. This is because mushroom myce- lium has the ability to decompose difficult to degrade nutrients such as cellulose, hemicellulose and lignin, whereas many other micro-organisms can only survive on easy to degrade nutrients. And it is these easy to degrade nutrients especially that are combusted during fermentation, so they no longer form a nutrient source for competitor moulds. Nitrogen and moisture are necessary to combust simple sugars. If chicken manure or water is not properly distributed, patches of compost will form with a too high ammonia concentration or where fermentation leaves behind too many carbohydrates. On the one hand, this gives compost patches which are more difficult for the mushroom mycelium to colonise, and on the other patches occur where undesirable microflora can rapidly develop. During the fermentation process, the compost
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