Cultivation Theory: 4. Compost Heat Treatment and Inoculation

Compost Heat Treatment

After weighting the material it can be soaked into water for several hours (recommended) or it can be directly sent to heat treatment.
There are several methods of heat treatment but here I will show you only two of them because they are widely used in the household system:

1. Direct flame heating (as shown in fig. 15): The material is placed into a container (usually a metal barrel, or an improvised boiler) half filled with water and it is soaked by using a grill placed on the top of it which is designed to keep the material under water, then everything is covered up with a lid for an appropriate heat treatment.
2. Scalding the material into hot water: the same procedure as described above should be used here too.

Fig. 15. Substrate pasteurization on direct flame
(Photo credits: www. fungiforum.com)

Heat the content of the barrel until the temperature reaches 80-85 ºC / 176-185 F and try to maintain this temperature for about 2 to 4 hours. If the treatment temperature is lower, then allow more time for heat treatment process. This way occurs the so called 'substrate pasteurization' and this step is important because kills competing fungi and bacteria present into the substrate mass. However this temperature doesn't kill some bacteria species useful for the mushroom cultivation process.

Note: Another heat treatment procedure is to sterilize the material by boiling it for several hours or rising the temperature to 121ºC / 249.8 F for about 30 minutes to 1 hour. However, this procedure is not suitable for backyard mushroom cultivation.

Preparing the Compost for Inoculation with Mushroom Mycelium

The house backyard mushroom cultivation is a concept based on ideas and lots of improvised tools in order to make the whole process easier.
One of such improvised tools is the wire mesh container which is filled up with material and soaked under water during heat treatment. This has the ad-vantage that allows water flow immediately after heat treatment. Thus through a rope system it can be lifted up from the boiler and kept in the air while water is licking away (see Fig. 16). It also has the advantage of removing all material from the barrel after heat treatment.

Fig. 16. An improvised wire mesh container filled up with straw
(Photo credits: www.fungiforum.com)

Caution: All operations that we undertake from now on (draining, inoculation, weighing, etc) should be performed in clean conditions in order to avoid substrate infection with molds, germs and bacteria; otherwise all of our work until now could be compromised. This is why containers and all tools that the pasteurized material enters in contact with should be clean enough to ensure mushroom cultivation suc-cess.
A first step is to clean up container surfaces with 90º alcohol or some other germ killing substances (however, these should be oyster fungus friendly substanc-es designated only against competing fungi or bacteria).
Wash hands with soap and water then spray them with alcohol or use a pair of gloves.
After pasteurization, allow material to cool down preferably on a clean con-crete surface covered up with a clean plastic wrap, or a specially designed table for this purpose (see Fig.17). Disperse the material on the table in a layer of 20-30 cm / 7.9-11.8 US inch thick in order to cool quickly.

Fig. 17. Material left to cool down on an improvised table designed solely for this purpose(Photo credits: www.fungiforum.com)

! Check the substrate before inoculation:
• The material when squeezed into our hands should not show any water drops;
• The smell should indicate a freshly humidified substrate and should not have any sour odor indication the start of decomposition process.

Note: How will you know if you did the right thing so far?
Water should not accumulate at the bottom of the plastic bag that is going to be introduced in (waste bag, customized plastic bag, etc).
When the substrate temperature drops down to ca. 20-25 ºC / 68-77 F the material is cool enough to be weighted and inoculated with mushroom mycelium (spawn).
In order to know the exact quantity of compost, it is recommended to weight materials in a wet state separately and then to mix them up.

Adding Supplements and Mycelium to the Substrate

1. Immediately after mixing up the substrate ingredients we will add to the substrate mixture gypsum at a rate according to the chosen formula (usually 4-5%) mix well and we are ready to go further with the inoculation step.

2. Now take a pair of disposal gloves on your hands and carefully take the mycelium out of the jar or bag. Care should be taken not to damage the hypha of mycelium surrounding the grain kernels or other support on which it is growing. Mycelium is a living organism, therefore if damaged the mycelium won't be able to spread throughout the compost and this will result in low mushroom yield.

3. Now weight the mycelium and use the desired quantity (usually 2-3% = 2-3 kg / 4.4.-6.6 lbs to 100kg /220 lbs of compost)

4. Next add the weighted mycelium quantity to the readily pasteurized and cooled substrate that has been mixed up with gypsum (see Fig.19). Mix everything together and disperse the mycelium in the whole substrate mass.

Fig. 18. Adding mycelium to the straw based substrate
(Photo credits: www.wildbranchmushrooms.com)

! Remarks:
a) If you will increase the amount of mycelium added to the substrate from 1.25% to 5% automatically the mushroom production will increase by about 30-50%. In addition this will reduce the time necessary for spawn to colonize the substrate during incubation and will prevent contamination by competing molds, bacteria or insect occurrence in the substrate.
b) If you won't take into consideration the first remark, the competing spe-cies might take control of part (10-20%) of your bags filled up with inoculated sub-strate. When this happens, the oyster mushroom mycelium stops or reduces its development. However, such situations occur, even if you did everything right, so there's no need to panic if you find 10-20% of your bags are infected with molds or such contaminants. Don't get discouraged, but try to think of what did you do wrong or how could you improve your mushrooming experience. From time to time even the experienced mushroomers are dealing with such situations.

The Mushroom Mycelium: What is It? and Where Can It be Purchased?

Once you know exactly what species of mushroom you will cultivate, the next step is to procure mycelium (spawn or mushroom seeds). However, before purchasing mycelium you should know few things:
• Check the provenience of the mycelium. A pure mycelium is the result of its preparation in laboratory conditions; therefore you should purchase it from companies that you trust;
• Make sure that your mycelium is fresh (it has a warranty of about 2 months);
• Another important aspect refers to transportation: this should be made in proper temperature conditions (2-4 C / 35.6-39.2 F);
• Do not accept damaged bags of mycelium;
• Make sure that you've got the best strain, this will influence your mush-room production.

Where do we get the mycelium from?

You can get mycelium from various sources of producers or cultivators.

Here are some mycelium producer addresses that might help you:

http://www.fungiperfecti.com/
http://www.italspawn.com/ita/
http://www.sylvaninc.com/

If you are not pleased with buying spawn whenever you want to grow mushrooms you can build your own lab with less than $400, in order to find out how visit the Consulting page

How much mycelium should you purchase?
As a beginner cultivator you should purchase a small amount: 3-5 kilos /6.6-11 lbs are sufficient for the inoculation of 20 substrate bags each one of them weighting 5 kilograms /11 lbs.
Note: Once purchased mycelium should be kept in the fridge and taken out with up to 24 hours before usage.

Preparing the Compost Bags for Incubation

Once prepared the compost mixture is inserted into trash bags or column type customized bags (about 4-10kg / 8.8-10 lbs of material in each bag). The bags are then bound to their end by using a rope.

Note: Preferably use transparent polyethylene bags for a good visibility. This is important because you can easily detect any infection in time. In case of contamination remove the bag out of the incubation room. Another advantage of the transparent plastic is that you can observe the spawn run through the compost mass.

Fig. 19. Inserting the inoculated compost into polyethylene bags
(Photo credits:www.fungiforum.com)

Fig. 20. Inserting the inoculated compost into polyethylene bags
(Photo credits:www.fungiforum.com)

Next take the bags and make wholes on their surface with a diameter of 1-2 centimeters / 0.4-0.8 in and distribute them in zigzag at distances of 10-15 cm / 3.9-5.9 inches one from another. Make rounded wholes or cross shaped wholes. The latter variant is superior to the first one because it reduces the chances of compost to lose humidity especially in the warm season.
The mycelium hypha in order to grow requires nutrients, moisture, temperature, oxygen and pathways for elimination of metabolic substances resulted from their development process such as carbon dioxide and metabolic water. Therefore the role of the holes is to allow gas exchange in the substratum.

Note: The size of the bag also has its significance. A good habit is to think about balance: a small and narrow bag will quickly dehydrate (especially in sum-mer), on the opposite, a big and thick bag prevents good ventilation. Having in mind this simple principle most mushroomers are using bags measuring 40-50 cm /15.7-19.7 inches in diameter and 70-80 cm 27.6-31.5 inches long.