How to make an oyster mushroom substrate

How to make an oyster mushroom substrate

YouTube says it’s simple:

  1. pour boiling water over the components that were at hand (leaves, cardboard, shavings, sawdust),
  2. held for 5-8-12 hours (each mushroom grower recommends different numbers),
  3. you can make mushroom bags.

On the picture: an example of how NOT to do steaming.

What substrate is suitable for mushrooms?

The best result at home gives a substrate of sunflower husks.

It has much less mold spores than straw. Therefore, it takes only 3 hours to heat the husk. And straw – at least 6 hours.

The yield of mushrooms on the husk is higher than on straw.

Be sure to add legume grass hay to the straw to increase the yield.

If you watched a video on YouTube and want to make a substrate from sawdust, foliage, paper, make small portions. You will most likely have to throw out those experimental bags.

If there are few of them, you will not be so sorry for your costs and labor.

How to make a substrate easily?

You can do everything as you read on the Internet, and see for yourself: the first month, maximum two, the blocks will overgrow.
The substrate will then overgrow with dark spots in which bacteria grow. Or trichoderma (green mold) will appear on the substrate.
Therefore, making a substrate “quite easy” will not work.

Read also the article “What is the best composition of the substrate for oyster mushrooms?”
Please use google translate!

Why do we steam raw materials?

We need to destroy the competitors of oyster mushroom mycelium: mold spores and bacteria.

It is impossible to heat raw materials during heat treatment above 75C.

At the same time, some of the spores not only survive, but also receive thermal activation – after cooling, they swell and grow faster and more aggressively than the rest of the spores.

How to make mushroom blocks without defects and spoilage

  1. Heat treatment of raw materials must be carried out by hydrothermal method.
    The technology is described in detail here * (link below). It is important to follow all the recommendations from the article, as they are equally essential.
  2. If you didn’t have enough mycelium, or the bags ran out, and the steamed raw materials are still left, you will have to throw it away. You can’t steam it again!
  3.  The time required for heat treatment does not depend on the volume of the container.
  4.  The tank, barrel or bath in which heat treatment is carried out must be completely (the lid too) pasted over with foam plastic or foil glass wool.
    If the container is not insulated, then near the walls the raw material will cool faster, part of it will not warm up, and the likelihood of damage will increase dramatically.

    If you steam raw materials in a two-hundred-liter barrel, you can make 5, maximum 6 mushroom blocks weighing 8.5-9 kg.

5. If you have just started growing oyster mushrooms, you can steam the raw materials by pouring hot water over them.
In doing so, be sure to:

  • water must be heated to such a temperature that after you pour it into the raw material, the temperature of the raw material is at least 73-75 degrees;
  • the container must be insulated. This is necessary for high-quality heating of the entire volume of the husk and so that the temperature does not drop during heat treatment;
  • keep the sunflower husk at this temperature for at least 4 hours.

    If your raw material is straw, I do not recommend this method at all.

  • Immediately after the raw material has been steamed, the empty barrel (container) must be washed with clean water and treated with a solution containing sodium hypochlorite. For example, Domestos. Dilute in water as instructed.

substrate for oyster mushroomBut this method is possible ONLY if there is a special room for inoculating mycelium into the substrate – a clean zone or also called a sowing zone. It must be constantly treated to kill mold spores and bacteria.

Unfortunately, even the presence of a clean zone does not guarantee that by pouring raw materials with hot water, you can avoid the appearance of green mold, non-growth spots, and bacterial infection.

If this happens, you will have to switch to hydrothermia*.

You see in the photo – inoculation takes place outdoors
Heat-treated straw is not even covered.

There will definitely be problems in a few months of such work.

Why do spots appear in the substrate?

Mold and bacteria spores are covered with a thick shell and die at a temperature of at least 121 degrees for 40 minutes.
Therefore, when pouring straw or husks with boiling water (or hot 85-90 degree water), we get rid of only those spores that have swollen or hatched from the shell at the time of heating.
The rest of the spores can germinate simultaneously with the mycelium, and make it a significant competitor.

The longer you grow oyster mushrooms, the more mold and bacteria spores accumulate.

There remain spores that are more resistant to heat treatment.

In the room where the inoculation takes place, spores are most dangerous. Due to high humidity, their number increases.
When germinating, the hyphae of both spores and oyster mushroom mycelium secrete certain substances that inhibit the growth of competitors. It is not always possible for oyster mushroom mycelium to win this fight.

pH in the substrate should be in the range of 7.8-8.2

If there are no problems with overgrowing of the substrate, most likely the pH is in order.
But, when green mold (Trichoderma) appears in the bags, it is necessary to buy a pH meter and measure the alkalinity of the substrate before stuffing.
Read more about pH-substrate here.

Why you do not need to add chalk and gypsum, read here. Section “Chalk and gypsum for oyster mushrooms”.

* An article about the hydrothermal method