Are you interested in how to grow oyster mushrooms on straw? One major part of the process is knowing how to treat the straw substrate accordingly

Oyster mushroom cultivation on straw can be broken into four parts, treatment of the straw, inoculation, incubation, and fruiting. Each step is crucial to the next and affects the overall yield.

Today I am detailing the process of straw treatment for those interested in how to grow oyster mushrooms on straw. The first step is to source your straw and chop it well. Then it is time to treat the straw. By treating the straw microorganisms are killed and competition for the available nutrients is limited. I provide four methods for treating straw below.

How to grow oyster mushrooms on straw: 4 straw treatment methods to know about

1) Hot water pasteurization: Using a 55 gallon drum raised up on cinder blocks and a turkey burner below about 30 gallons of water is brought up to 180 degrees F. Two burlap sacks of straw are then submerged in the barrel and the heat is turned off. A top is placed on top of the barrel and the water is maintained above 145 for two hours. We did not need to turn the heat on after submerging the straw in 180 degree F water. (figure 10)

2) Hydrated lime: Soak 2-3 burlap sacks of straw are placed in a 55 gallon barrel. 1 Gallon of hydrated lime is mixed with water in a 5 gallon bucket, the lime is dissolved and slowly added to the 55 gallon drum as it is filled with water. The barrel is filled until the straw is completely under water and the solution is at a pH of 12-13. The straw is left to soak for 16 hours. It is critical to use hydrated lime with magnesium content below 10%.

3) Cold fermentation: Straw is submerged in a 55 gallon barrel of water for 5-8 days until the smell of fermentation is apparent.

4) Wood ash soak: This method is the same as the hydrated lime soak but instead of using lime wood ashes are used. We found it difficult to bring the pH to the necessary level using wood ashes. Close to 4 gallons of ashes was used for a 55 gallon barrel raising the pH to about 11. The straw was allowed to soak for 16 hours.

In pasteurization, which is the standard for straw treatment, the temperature is raised to kill all of the mesophilic organisms but not reach temperatures to activate the thermophilic organisms. By killing the mesophilic organisms the mushroom mycelium has a clean substrate to grow onto. With the lime soak and wood ash treatment the pH spikes and bursts the cell walls of the microorganisms. Once the straw is drained the pH lowers back to 7 a suitable place for mycelial growth.

To kill the microorganisms using fermentation an anaerobic environment is created by submerging the straw for five days. All aerobic organisms die and the anaerobic ones come alive. Once the straw is removed from the water the anaerobic organisms die as well. All four of these treatments in theory leave the straw free of competing organisms for the mushroom mycelium to grow uninhibited. In practice the lime and heat treatments were much more effective at doing this than the fermentation or wood ash soak.

straw treatment: biological efficiency

The highest biological efficiency achieved, 65% used the lime soak and Pleurotus ostreatus Elm A. Of the 8 bags inoculated in total 15 pounds was harvested. If this treatment method and strain were used continuously a grower would likely increase this biological efficiency to 100%. By sticking with a certain strain and method of treatment the grower can fine tune their system to be the perfect set up for that particular mushroom. The average biological efficiency over all the trials is shown in table 3.

Efficacy is measured through biological efficiency. This is calculated by dividing the total harvest by the weight of the dry substrate. Each bag used in these trials weighed 10 lbs with a moisture content of about 70%. So each had 3 lbs of dry substrate. To achieve 100% biological efficiency 3 lbs of fresh mushrooms would need to be harvested off of each bag.

There are two major factors that may have influenced the yields of these trials. These numbers include the bags which were contaminated and did not fruit at all. The number of completely contaminated bags was much higher for the fermentation and wood ash treatments compared to lime.

BE by treatment

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