Black peat
Black peat, which was formed up to 10,000 years ago, is widely used in mushroom cultivation and is mainly harvested in the northern hemisphere. It is heavy and feels moist when handled, with a firm structure. If you knead it into a ball and throw it against a wall, it will stick.
Black peat absorbs water slowly but retains it very effectively once absorbed. Right after moistening, its surface appears shiny, but after about 24 hours it becomes dull—an indication that the water has been gradually absorbed. This behavior is the result of the fine capillary pores in the peat, which cause water to enter and be released at a slow pace.
White Peat
White peat, which is younger (up to about 5,000 years old) and far less decomposed than black peat, feels dry to the touch. When kneaded into a ball and thrown, it immediately falls apart.
Unlike black peat, white peat absorbs large amounts of water very quickly, but also releases it quickly. Because of this, it is less suitable for long-term moisture retention. White peat is therefore often used in gardening and as a base material for potting soil.
Influence on the casing soil
The type of peat influences the height and structure of the casing soil layer.
Black peat
When black peat is incorporated into the casing soil, less material is needed per cubic metre to create a higher layer. In the case of heavy casing soil, the height is only 4.3 cm per m³, but in practice, the layer height after filling often measures 6 to 7 cm. During cultivation, the layer settles slightly, but this is limited. The difference arises because black peat often contains coarse clods of 2 to 4 cm. Air remains between these clods, making the layer higher and airier.
White Peat
With white peat, the effect on the casing soil layer is very different. White peat does not contain coarse clods but consists of fine material. As a result, the spaces within the layer are completely filled, creating a denser and less structure.
This difference has important consequences for cultivation: watering, mycelium growth, and the approach to ventilation differ significantly compared to casing soils with black peat. These differences ultimately influence the cultivation system as a whole.
Black peat
With casing soil containing black peat, it is possible to apply more water before use and at the start of cultivation. After cooling down, almost no water is added till moment of harvesting. Watering resumes only when the mushrooms reach a size of about 1 cm and the compost temperature begins to rise. In many cases, white mushrooms are not watered again until after the first flush has been harvested.
White Peat
With casing soil containing white peat, water must be applied every other day, even after cooling down. If this is not done, the casing soil will dry out very quickly.
Cultivation Challenges with White Peat
Whether white peat has only disadvantages depends greatly on the circumstances. When compost quality is excellent and the climate is well controlled, white peat often becomes the limiting factor. With white peat, it is much more difficult to manage pinning effectively. Producing multiple generations of mushrooms within a single flush—and thereby harvesting over a period of five to six days, it is virtually impossible with white peat. This is, however, achievable when heavier types of peat are used.
Possible Advantages of White Peat
On the other hand, if compost quality is not always optimal and mycelium growth is more difficult, white peat can offer certain advantages. Because it forms a lighter casing soil, the mycelium is able to grow through it more easily.
You should therefore only switch from white peat to heavier black peat if you have good, consistent compost. Do this step by step, for example by starting with 20% heavier casing soil mixed with the white peat. If you notice that this works well and leads to better production and quality, you can continue to 40%.
Final Note
Remember, you didn’t learn to walk in a single day, it took trial and error. The same is true for mushroom cultivation. Don’t give up if everything doesn’t go perfectly at first; what matters is that you are moving in the right direction. In the long run, using heavier casing soil will lead to better production and higher quality.
Mushroom Blog | Mark den Ouden
