How much calcined soda or lime do I need to add when soaking the substrate for oyster mushrooms?

How much calcined soda or lime do I need to add when soaking the substrate for oyster mushrooms?

Substrate produced from any plant material (sunflower husk, straw and their mixture with hay) should have a pH in the range of 7.8-8.2 after any treatment method. Therefore, the quantity of lime or soda to be added depends on your water alkalinity. It is necessary to send it for analysis. If it is neutral (7) or alkaline (7 and above), then you should start adding these components at a quantity of 100 grams per 100 kg of the ready substrate. You should look at the result: in case the substrate pH is still low, increase the lime (or soda) dose by one and a half times. Repeat the experiment, gradually increasing the dose until the pH of the substrate becomes 7.8-8.2. After you have determined the right amount of soda (lime), do not forget to control the pH of each inoculation. You can change the pH of the water or the raw material composition – for example, if the sunflower husk contains residual oil, part of the lime will enter the saponification reaction, and this will affect the pH of the substrate.

If the substrate pH is above 8.5, the oyster mushroom mycelium starts to become suppressed, and the higher the alkalinity, the stronger the mycelial development is inhibited, until its death (pH> 12).

If pH is lower than 7 – the development of molds is activated.


In what form form it should be added?

A solution of technical (calcinated) soda or a solution of lime paste is used. The paste itself can be bought in ready-made form or obtained from quicklime by slaking it.

  • In case of hydrothermal treatment – add a solution at the stage of filling dry raw material in bags, or add it in the heated water. In the second case, you may need a larger amount of lime or soda and it also takes more time (2-3 extra hours) to soak the raw materials.
  • In case of xerothermal treatment- add components into the water, used to cool the substrate.
  • In case of tunnel pasteurization – add lime or soda when you are soaking your straw.