How to grow mushrooms on untreated pelleted sawdust
What you need:
This "cold" method requires no heat or chemical (lime or hydrogen peroxide) treatment because the sawdust has already been subjected to pasteurization temperatures and thorough drying when it is made into pellets. Mold spores are going to be present in the mix, but I can out-grow them by using plenty of quality grain spawn, and by creating environmental conditions that favor the mushroom mycelium. Favorable conditions are influenced by these 4 factors:
- Temperature. Heat favors mold. Keep it cold. Heat treatment, such as boiling or steaming, may initially kill many resident contaminants, but the long cool-down (especially for sawdust substrate) favors mold growth. With the pellets, it is faster to hydrate them with warm or hot water, but it is easily observable that any additional heat leads to increased contamination.
- Air. Good airflow favors mushroom mycelium. With the Reishi, I tried sealing the sawdust and spawn in a filter-patch bag, instead of an arrow-punctured bag. The sealed bags were consistently contaminated to beyond 25% visible mold. However, I found Turkey Tail does well in both kinds of bags.
- Moisture content. Keep the mixed substrate at 52-55% water by weight. Too dry favors mold and too wet can favor bacterial contamination and slow growth at the base of the bag.
- Carbon-Nitrogen ratio. I have found that an increase in protein supplementation increases contamination rates. In addition, at least for turkey tail, the increase in protein definitely does not increase the yield.