Peat is the best casing material; it has more advantages compared to the other materials. Due to its properties, peat can hold a great amount of water and gradually give it up. The peat's pH level is very low; hence, there are practically no pathogenic organisms in it.
There are many kind of peat. Let's highlight three basic ones:
High-moor peat - a high moisture capacity and pH level, a low ash content (a low rate of decomposition), and almost no pathogenic organisms present.
Valley peat - low moisture capacity and pH level, a high rate of decomposition (ash content), a more optimal structure, and might contain pathogenic organisms, especially on the surface layer.
Transition peat - the name speaks for itself, it's something between the high-moor and valley peat.
Peat is also classified according to its origin:
It can be arboreal, sphagnous and sedgy. More detailed information about peat can be found in any agrochemical guide on organic fertilizers.
It's advisable to know that there are two basic methods of peat preparation – milling and bucketing. Milled peat is small, while bucket peat consists of large pieces.
Before preparing the peat for the use in mushroom cultivation, it's necessary to remove the upper layer 60 cm thick, because it contains a great amount of pathogenic organisms, which can cause irreparable harm to the mushroom culture in the cultivation process.
To prepare the casing layer, mushroom growers usually use the mixture of high-moor and valley peat in various proportions, which are determined by the properties of these kinds of peat and the mushroom cultivation conditions.
We intentionally don't specify the numbers of these correlations, hence in every industry, different kind of peat is used, and there is also an individual mushroom cultivation technology and individual proportions.
In order to regulate the pH level and to improve the structure of the mixture, chalk, ground lime, crushed dolomite, marl and quicklime are added as a lime component. The lime that is being used for the casing layer must the have the calcium content of not less than 20 %, and the magnesium content of not less than 5%. The amount of lime to be applied is determined through laboratory test of each new batch of peat.
For the making of casing layer in regions where there is a sugar factory, the waste products of lime (defecate) are used instead of lime itself.
Defecate usually consists of very small particles the size of 1 to 8 micron (0.001-0.008 mm), and therefore, it has a structure similar to clay's. At changing the quantity of defecate in the casing mixture, it can be given more or less dense structure, which will affect the size and quantity of mushrooms. A high percent of defecate in the casing mixture makes the layer's structure denser and as a result, large mushrooms grow in small amounts, and conversely, at a low content of defecate, the casing layer is less dense, which makes mushrooms of small size grow in big amounts.