Making mushroom substrate, particularly a bulk substrate like the popular coco coir, vermiculite, and gypsum (CVG) mix, is a key step in cultivating many mushroom species.
Creating mushroom substrate involves selecting the right materials, mixing them correctly, and often pasteurizing the mix to prepare it for colonization while preventing contamination.
Essential Ingredients
A common and effective bulk substrate recipe uses a blend of natural materials:
- Coco Coir: Provides the primary structure and retains moisture well.
- Vermiculite: Helps retain moisture and adds air pockets, improving aeration.
- Gypsum: Acts as a pH buffer, provides minerals, and helps prevent clumping.
- Water: Used to hydrate the dry ingredients to the proper moisture level.
Step-by-Step Process for CVG Substrate
Here's a general outline for making a coco coir, vermiculite, and gypsum bulk substrate:
- Gather Your Materials: Collect the required amounts of coco coir, vermiculite, gypsum, and hot water. Ratios vary, but a common starting point might be 1 part coco coir, 1-2 parts vermiculite, and a small amount of gypsum (around 5% of the dry weight).
- Hydrate the Coco Coir: Place the dry coco coir brick or loose coir into a clean container, often a large bucket. Add the calculated amount of hot or boiling water. The heat helps hydrate the coir quickly and can begin the pasteurization process.
- Mix in Vermiculite and Gypsum: Once the coco coir is mostly hydrated, add the vermiculite and gypsum to the container.
- Mix Thoroughly: Mix all ingredients together until uniformly distributed. Ensure all dry spots are hydrated. The final mixture should be moist enough that a squeezed handful releases only a few drops of water (this is known as "field capacity").
- Pasteurization (Using the Bucket Method): This is a crucial step to kill off competing microorganisms while leaving beneficial ones intact.
- Place the mixed substrate in the bucket.
- Close the lid on the bucket.
- After that, some growers, as shown in the reference, like to wrap the bucket with a towel. The reference notes, "i think that this helps aid the pasteurization." This insulation helps the hot water maintain a pasteurizing temperature range (typically 140-165°F or 60-74°C) for several hours as it cools slowly.
- Cooling: Allow the substrate to cool down to room temperature before using it. This can take several hours or overnight. The substrate is ready when it's cool to the touch.
- Use or Store: Once cooled, the substrate is ready to be mixed with colonized grain spawn. If not using immediately, it can often be stored in a clean, sealed container for a short period.
Why Pasteurize?
Pasteurization is different from sterilization. Sterilization kills everything, including beneficial microbes. Pasteurization aims to reduce the number of competing organisms (like bacteria and molds) while leaving some less harmful bacteria that can help the mushroom mycelium colonize the substrate more effectively and resist future contamination. The bucket method described in the video is a simple way to achieve pasteurization by using the heat from the hot water and insulating the container.
By following these steps, you can create a nutrient-rich and properly prepared substrate for your mushroom cultivation project.
