Detailed Explanation of the Latest Key Cultivation Techniques for King Oyster Mushroom
I. Morphological Characteristics
The fruiting bodies of the king oyster mushroom grow singly or in clusters. The cap is 4cm—6cm wide, initially round, later flattening out with a slightly depressed center, covered with fine down, ranging from black tea color to grayish brown, with white flesh; the stipe is central to off-center, club-shaped to bulbous, white and smooth, with a round cross-section and firm flesh; the stipe is 5cm—12cm long and has no annulus.
II. Biological Characteristics
1. Nutrition
The king oyster mushroom has a strong ability to decompose cellulose and lignin, and requires abundant carbon and nitrogen sources. Especially when nitrogen sources are abundant, the mycelium is thick and white, grows quickly, and fruiting body yields are high. Generally, crop straw supplemented with rice bran, cornmeal, wheat bran, etc. can all be used for cultivation and production.
2. Temperature
Temperature is a crucial factor in the success or failure of king oyster mushroom cultivation, and is key to determining growth and development and achieving high and stable yields. The mycelial growth temperature is 25°C, the temperature for fruiting body formation and growth is 10°C—18°C, with the optimum being 12°C—15°C. Below 8°C, fruiting bodies do not form and are difficult to grow; above 20°C, under high humidity conditions, the stipe softens, shrinks, easily turns yellow, and may even rot.
3. Humidity
During the mycelial culture stage, the moisture content of the substrate should preferably be 60%—65%, but since water should not be sprayed directly on the mushrooms during cultivation and moisture is mainly supplied by the substrate, the moisture content of the substrate is generally controlled at 65%—70% in actual cultivation. During the fruiting body formation stage, air humidity should be increased, generally controlled at a relative humidity of 90%—95%, and during the fruiting body growth stage, 85%—90% is preferable.
4. Light
Like other edible fungi, the king oyster mushroom does not need light during the mycelial growth stage; mycelium grows faster under dark conditions. However, the fruiting body formation and development stage requires a certain amount of scattered light stimulation. It is generally required to control it within the range of 300lx—1000lx. If the light is too strong, the cap turns black; if the light is too dim, the cap turns white and the stipe becomes too long.
5. Aeration
Both mycelial growth and fruiting body formation require a certain supply of O2, especially during primordium differentiation and formation, when sufficient O2 is needed. With poor O2 supply, mycelial growth is slow, and fruiting bodies are prone to small mushroom bud shrinkage and deformed growth.
6. Acidity and Alkalinity
The most suitable pH for the king oyster mushroom is PH6.0—6.5. It can grow normally within the PH4—8 range. Below PH4 or above PH8, fruiting becomes difficult. In actual cultivation and production, to prevent the substrate from becoming too acidic due to acid production during mycelial growth, the substrate PH is generally required to be within the range of 6.5—7.5.
III. Cultivation Season and Site
Based on the suitable growth temperature for king oyster mushroom cultivation, under natural conditions, autumn cultivation is more suitable. Temperatures that are too low or too high are both unfavorable for mycelial growth and fruiting body formation. If the first flush mushroom buds cannot form and grow normally, it will affect the occurrence of the second batch of mushroom buds. In the north, bag preparation and mycelial incubation are generally chosen in late July or early August, with fruiting in September. Cultivation can also be chosen in late spring and early summer, but because the suitable temperature period at this stage is relatively short and pests and diseases occur more frequently, this period is generally rarely chosen. Of course, if constant temperature conditions are available, cultivation can also be carried out in all four seasons.
The cultivation site can be chosen according to specific circumstances; a clean room or plastic greenhouse will do. The cultivation site must have sufficient ventilation facilities and shading conditions. When scattered light is needed, the shading material should be opened appropriately.
IV. Cultivation Techniques
1. Spawn production: The mother culture uses PDA medium, cultured at 26°C for 10d—13d to fill the test tube. The stock culture can use ordinary sawdust and wheat bran medium. To accelerate mycelial growth, wheat grains can be used as the medium. Generally, the stock culture at 26°C takes 30d—35d to fill the bottle. Each mother culture can inoculate 3—6 bottles of stock culture, and each bottle of stock culture can be transferred to about 20 fruiting bags.
2. Raw materials and preparation: There are many suitable growth substrates for the king oyster mushroom, including various agricultural and sideline product by-products such as broadleaf sawdust, cottonseed hulls, bagasse, wheat straw, waste cotton, rice straw, soybean stalks, etc., with appropriate amounts of supplements such as wheat bran, rice bran, cornmeal, sugar, calcium carbonate, and gypsum powder added for cultivation.
Stock culture formula: cottonseed hulls 36%, sawdust 20%, wheat bran 20%, cornmeal 4%, sugar 1%, calcium carbonate 1%, PH7—7.5 Cultivation substrate formulas:
(1) Mixed sawdust 35%, soybean stalk powder 40%, wheat bran 20%, cornmeal 3%, sugar 1%, calcium carbonate 1%, moisture content 60%—65%.
(2) Mixed sawdust 38%, corncobs 38%, wheat bran 22%, sugar 1%, calcium carbonate 1%.
(3) Mixed sawdust 23%, corncobs 23%, wheat bran 19%, cornmeal 5%, sugar 1%, calcium carbonate 1%, soybean stalk powder 30%.
The stock culture is generally placed in spawn bottles, and the cultivation bags use 17×34 plastic bags, sealed with collar rings and cotton plugs.
3. Sterilization and inoculation
The filled bottles (bags) of substrate should be sterilized promptly. Spawn bottles or high-pressure polypropylene plastic bags can be sterilized under high pressure (1.5kg/cm2—2kg/cm2) for 2h, while low-pressure polyethylene plastic bags must be sterilized in a pressure cooker for 10h—12h. After cooling, inoculate under aseptic operation in an inoculation box or sterile room. After inoculation, place at 23°C—25°C for dark culture; generally about 35d to fill the bag. The culture site should be ventilated, and humidity should not be too high; around 70% is sufficient.
V. Fruiting Management
After the mycelium fills the bag, it can be moved into the mushroom house and measures taken to promote fruiting at a suitable temperature. Be careful not to arrange them too tightly, otherwise yield will be affected. If wall-type bag arrangement cultivation is adopted, generally the “alternating upper and lower bag opening method” is used for single-row bag stacking. Then open the doors and windows, strengthen ventilation, and increase the temperature difference to stimulate primordium formation. The specific method is to maintain the mushroom house humidity at 90%—95%, and spray water mist into the air and on the ground. Generally after 10d—15d, buds will appear. During this stage, maintain the temperature at 12°C—15°C. When the primordia form inside the bag and 1cm—2cm small mushroom buds appear, promptly remove the cotton plug and plastic collar ring, cut away the plastic bag above the substrate surface, and keep 3—4 relatively robust mushroom buds per bag. Note that the time of opening the bag is directly related to yield. If the bag is opened immediately after the mycelium fills it, it is difficult to form primordia or primordia form slowly, and fruiting is uneven. If the bag is opened after larger fruiting bodies have formed, it easily causes deformed king oyster mushrooms, or even shrinkage and rot. During the mushroom bud growth period, humidity of 85%—90% is preferable. To extend the freshness period of the fruiting bodies, 2d—3d before harvest, humidity should preferably be controlled at around 85%. The fruiting management of the king oyster mushroom specifically includes the following aspects:
(1) Temperature control: The mushroom house temperature directly affects primordium formation and normal growth and development of fruiting bodies. The king oyster mushroom fruiting body is relatively sensitive to temperature. It can grow normally within the 10°C—18°C range. Below 10°C, primordia are difficult to form. Above 18°C, the growth rate of existing unharvested fruiting bodies accelerates markedly, quality declines, the mushroom body is no longer white and firm, and yellowing and softening begin to appear at the neck of the mushroom body. Small mushroom buds stop growing, and primordium differentiation stops. At the same time, with high temperature and high humidity and poor ventilation, the disease resistance of fruiting bodies declines, making them susceptible to bacterial invasion. The cap develops mucus, and the mushroom body turns yellow and rots. At this time, pay attention to ventilation, widen the spacing between bags, and regulate the temperature through means such as opening and closing doors and windows, keeping the temperature within the 12°C—19°C range.
(2) Ventilation management: When fruiting body primordia are forming, focus on moisture retention and appropriately reduce ventilation. As the fruiting bodies gradually grow, appropriately increase ventilation to ensure fresh air in the mushroom house. With poor ventilation, fruiting bodies are difficult to grow and develop normally, and small mushroom buds are prone to shrinkage and growth cessation. If high temperature and high humidity occur as well, bacterial diseases are likely to result.
(3) Humidity management: During the fruiting body primordium formation stage of the king oyster mushroom, the relative air humidity in the mushroom house should be maintained at 85%—95%. If humidity is low, primordia are difficult to form, and fruiting bodies dry out, crack, shrink, and stop growing. To increase humidity, generally methods such as spraying into the air and wetting the ground are used. Newspaper or non-woven fabric can be used to cover the bag openings, while at the same time trying to avoid cold wind blowing directly onto the mushroom bodies. When the mushroom house temperature is high, water should not be sprayed directly onto the mushroom bodies, otherwise it easily causes mushroom rot.
(4) Light regulation: The fruiting bodies of the king oyster mushroom can grow and develop normally under a light intensity of 200lx—1000lx. Light regulation and control are generally carried out according to temperature. When the temperature is low, reduce the mushroom shed covering or open the mushroom house to regulate temperature; when the temperature is high, increase shading, close the sunny-side doors and windows during the day, and then open the doors and windows for ventilation in the evening.
In fruiting period management, all factors should be considered comprehensively, while also focusing on the main factors and seeking the best solution among contradictions. This requires managers to be careful and conscientious, continuously exploring and summarizing experience; only in this way can fruiting be ensured.
VI. Harvesting and Processing
Harvest when the cap has expanded flat, the edge is slightly incurved, and the spores have not yet been discharged. It can be sold after refrigerated preservation at 2°C—4°C. Harvesting appropriately early gives the mushroom better flavor and a longer shelf life. Compared with general mushrooms, the king oyster mushroom keeps for a longer time. It can also be sun-dried (oven-dried) or made into cans. After the first flush is harvested, clean the substrate surface, remove contaminated bags, and adjust the temperature, humidity, ventilation, and light of the mushroom house properly. After 10d—15d, the second flush can grow. Generally after one flush, the bags have become severely lighter, and water and nutrient solution should be replenished in time. However, because after the first flush the mycelium in the bags is highly susceptible to contamination by foreign fungi, and the yield of the second flush is relatively low, the yield of the king oyster mushroom is mainly concentrated in the first flush.