Mushroom Compost Bedding and Spawning Techniques

1. Mushroom house disinfection

Before bringing in the compost, the mushroom house must be cleaned thoroughly. The surrounding walls and growing beds should be brushed or coated with bleaching solution or limewater for disinfection. Some lime should be scattered on the floor and wall bases, and a 20-times dilution of dichlorvos solution sprayed to kill insects and sterilize. Then close the doors and windows, and fumigate with 500 mL of formalin per 100 cubic meters of mushroom house. The specific method is to pour the formalin into an iron pot, add 5 times its volume of water, heat it on a charcoal stove, and let the formalin diffuse through the mushroom house with the steam. After 1 to 2 days, open the doors and windows for ventilation. Some mushroom houses are simply constructed and difficult to seal; in that case, spray the surrounding walls and mushroom beds with a 50-times dilution of lime-sulfur mixture.

2. Putting the compost on the beds

Before the compost is put on the beds, the transport tools should be disinfected. Move quickly during handling to avoid excessive loss of heat from the compost pile. After carrying it into the mushroom house, immediately pour it onto the mushroom beds to a thickness of about 12 to 15 cm, layering the compost from top to bottom to avoid the hot steam making operation uncomfortable. For compost that has not undergone secondary fermentation, after putting it on the beds, the doors and windows should still be closed for a 2 to 3 day sweating period. Also fumigate with sulfur or formaldehyde; generally, for every 100 square meters of growing area, use 1.5 kg of sulfur mixed with 0.25 kg of sawdust and fumigate for 24 hours, or use 1 kg of formalin with a formaldehyde content of 40%, place it in an iron pot and steam it to let the gas spread through the room. After disinfection, open the windows for ventilation, and once the temperature drops below 28°C, spawning can begin.

3. Spawning

(1) Timing of spawning  Spawning too early, when the temperature is too high, can easily cause mushroom death. Spawning too late delays fruiting and affects yield. Based on the requirements that the optimum temperature for mushroom mycelium growth is 23 to 25°C and the optimum temperature for fruiting body formation is 13 to 16°C, the suitable spawning period is one in which there is a temperature condition suitable for mycelium growth after spawning, and about one month later the temperature gradually drops to suit fruiting body formation. The specific time varies with the climate conditions of each region. In the southern provinces, the spawning time is roughly between September and October.

(2) Spawning methods  There are three types: drill spawning, hole spawning and broadcast spawning. At present, hole spawning and drill spawning are most commonly used.  Hole spawning  Use your fingers to make holes in a square or plum-blossom arrangement, with a hole spacing of 10 to 12 cm and a depth of 3 to 4 cm, then insert a small piece of spawn, cover it well with compost and press flat. The top of the spawn should be slightly exposed to the outside to allow air circulation. Each bottle of spawn can inoculate 0.5 square meters.  This is currently the method commonly used in production.

Drill spawning  At a row spacing of 10 to 12 cm, first dig a shallow furrow, then scatter in the spawn, cover well with compost and press flat. Likewise, the spawn must not be completely covered; the top should be slightly exposed. This method saves labor, but the amount of spawn used is large, so it is relatively seldom used when spawn is insufficient.

Broadcast spawning  First loosen the surface of the compost to a depth of 3 cm, scatter in the spawn, then cover with a thin layer of compost and pat gently with the hand. Generally, wheat-grain spawn can use this method. After spawning, close the doors and windows for 3 to 4 days to help maintain the temperature and humidity of the mushroom house, allowing the mycelium to recover and colonize. After 6 to 7 days, check the spawn growth; if there are missing holes or missed spots, reseed promptly. If mold is found, increase ventilation, lower the temperature, and prevent the spread of the pathogen.

4. Casing soil

The role of casing soil is to increase the moisture of the surface layer of the compost, change the ratio of oxygen to carbon dioxide in the compost, promote the transformation of mycelium toward fruiting body formation, and support the mushroom bodies after fruiting. In addition, the casing soil itself has a certain weight and nutrients and can play a role in gravitational mechanical stimulation, microbial stimulation, and supplying mushroom nutrition. The material used for casing soil should be selected as soil that is moist but not sticky, dry but not crumbly, loose and air-permeable, with strong water retention, a certain fertility, and a pH of about 7.2. Generally, pond mud, peat soil, and loam or sandy loam that has grown leguminous green manure are best. Surface fertile soil has many pathogens and pests and is not suitable for use; usually soil from below 20 cm beneath the surface is taken. The collected soil is dried in the sun, crushed, and sieved through screens with different mesh sizes to divide the soil particles into two types: coarse (about the size of a broad bean) and fine (about the size of a soybean). Before casing, first adjust the moisture of the soil particles with 1% limewater; generally, the water content of the soil particles is required to be 20% to 25%.  The suitable time for casing is when the mycelium in the various holes can connect with one another and extend 5 to 6 cm into the compost layer, generally about two weeks after spawning. If casing is too early, the mycelium has not yet developed well; growth is slow, fruiting is delayed, and yield is not high. If casing is too late, the already mature mycelium lacks environmental conditions suitable for fruiting body formation, easily ages, and can also cause reduced yield.

When casing, first cover with coarse soil, and after the mycelium grows onto the soil, cover with fine soil. The suitable casing thickness is about 3.3 cm, with coarse soil accounting for 2/3 and fine soil accounting for 1/3. If the casing is too thin, it easily produces thin mushrooms, dense mushrooms, and opened-cap mushrooms. If the casing is too thick, fruiting is delayed and there are many deformed mushrooms. Generally, it is best that the coarse soil does not show the compost and the fine soil does not show the coarse soil.