Why is casing soil used? There are two main reasons: 1. the Pseudomonas putida bacterium; 2. to regulate evaporation. Mushrooms will not grow without evaporation. The casing soil structure, through the depth of casing and on the surface, is the factor that determines how much water can absorbed and released. This is also known as the water buffer. How can growers influence this effect?

Properties
Casing soil is made up of peat. Peat consist of many small and larger pores which act as communicating structures that affect the flow of water. The very tiny (micro) pores absorb water very slowly, but retain it for a long time. The larger (macro) pores can absorb water faster but release it again very quickly. In good casing soil, both properties are necessary: rapid absorption of water: during mycelium growth and after harvesting, and slow release: during pinhead formation and out grow, and when the mushrooms are harvested.

Air
What is the secret of casing soil? Ensure that the moisture content of the casing soil is good. With “export” casing soil, you have to apply enough water and mix the casing with a loader or bobcat. Ask the supplier for instructions and follow them correctly. This has already been done with casing soil delivered in bulk and ready to use. Casing soil is sensitive to structure loss just before it is applied. If the casing soil is compacted or compressed, the “air” will be squeezed out. This effectively closes off the very crucial micro pores. The casing soil will feel harder. During transport and filling avoid compacting the casing soil too much, for example when using augers, over-filling the hopper on the filler or in front of the levelling axle during filling.

Soft
Casing soil should feel nice and soft. Straight after filling, push your finger into the casing soil. You should be able to plunge your finger in easily and without resistance. Experience will teach you how to feel the difference. A good layer of casing soil after filling is about 6 cm thick. The amount ordered is much less, around 4.5 cm. The rest is air, and these air pockets can largely be filled with the water necessary for the mushrooms to grow!

Mark den Ouden
Mushroom Office
Master class course Mushroom composting and growing is 18 – 23 February, there are still some seats available! Please contact This email address is being protected from spambots. You need JavaScript enabled to view it. ASAP if you want to join! Next course will be 29 April – 4 May.