Detailed Explanation of Key Production Techniques for Buried-log Shiitake Mushrooms

I. Scope

This technique specifies the management standards for off-season soil-covered ground-cultivated shiitake mushrooms.

This technique applies to off-season soil-covered ground-cultivated shiitake mushrooms.

II. Selection of Cultivation Site

1. The cultivation site should be selected in mountain valley fields with a good ecological environment, fresh air, excellent water quality, uncontaminated soil, no various pollution sources within 300 meters, mountains to the east and west, relatively short sunlight exposure, and large temperature differences between day and night, with a water source preferably mountain spring water or reservoir water, relatively flat terrain, convenient drainage and irrigation, and convenient transportation.

2. Fields frequently hit by hail and prone to flooding should not be selected as mushroom farms.

III. Social Conditions

1. Farmers cultivating soil-covered shiitake mushrooms must have technical skills and capital, and comply with all regulations stipulated in the Measures for the Administration of Edible Fungus Spawn of the Ministry of Agriculture of the People's Republic of China.

2. Those without technical skills must undergo training, carry out cultivation under the guidance of technical personnel, or pair up with experienced cultivation households.

IV. Spawn Bag Production

1. Selection of cultivation season. To ensure normal fruiting from June to September, bag production from late November of the current year to early March of the following year is preferable.

2. Cultivation substrate. Use sawdust, napier grass, and cottonseed hull culture medium. Sawdust, napier grass, cottonseed hulls, wheat bran, corn flour, etc. must be fresh, dry, free from insect damage, free from mold and rot, and free from pesticide residues. Cultivation material formulas: A. Broadleaf tree (dry) sawdust 79%, wheat bran 16.56%, corn flour 2%, sucrose 1.2%, gypsum powder 1.2%, potassium dihydrogen phosphate 0.02%, magnesium sulfate 0.02%; B. Broadleaf tree (dry) sawdust 60%, napier grass (dry) powder 20%, wheat bran 13.49%, corn flour 1%, rice bran 2%, sucrose 0.8%, gypsum powder 1.6%, activated carbon 0.15%, plant ash 0.41%, potassium dihydrogen phosphate 0.15%, magnesium sulfate 0.15%, superphosphate 0.25%; C. Broadleaf tree (dry) sawdust 50%, cottonseed hulls 30%, wheat bran 17%, sucrose 1%, gypsum powder 1%, activated carbon 0.15%, plant ash 0.4%, potassium dihydrogen phosphate 0.15%, magnesium sulfate 0.15%, superphosphate 0.15%.

3. Bag filling. According to the selected formula, mix the culture material evenly with a water content of 60%. Bag-filling machine operation typically requires 2-3 people rotating, one person adding material, one person filling bags. During operation, one hand inserts the cylindrical bag onto the discharge port, while the other hand firmly pushes against the bottom of the bag during feeding, slowly pushing it backward until one spawn bag is full, then tie the bag opening tightly with fine yarn rope.

V. Sterilization and Inoculation

1. Sterilization. High pressure (1.5 Mpa, 125°C) sterilization for 2h or atmospheric pressure (100°C) sterilization for 10h-12h.

2. Inoculation. The inoculation environment must be clean, dry, and disinfected; after the material temperature cools to below 28°C, place into an inoculation box or sterile room; place an appropriate amount of disinfectant in the inoculation box or sterile room, seal and fumigate for 0.5h before inoculation; each bag of cultivation spawn inoculates 20-30 cultivation bags.

VI. Mycelium Cultivation

1. Cultivation room. Should be disinfected regularly, requiring cleanliness, dryness, ventilation, and light blocking.

2. Cultivation method. Inoculation surface facing up, stacked in a "#" shape pattern.

3. Cultivation management. The temperature of the spawn-running room should be 22-25°C, relative air humidity 65-70%; use straw curtains to block light, keeping the spawn-running room basically dark; open windows and doors in a timely manner for ventilation, maintaining fresh air in the spawn-running room; within one week after inoculation, check once while turning the stacks, promptly removing inferior spawn bags.

4. Removing tape for aeration. After 15-20d, when the mycelium has spread within the bag to a diameter of 8-10cm, one corner of the adhesive tape or tape paper attached to the inoculation opening can be peeled open to prevent insufficient oxygen in the spawn bag from affecting continued mycelium growth in the next stage; in some places, tape has been omitted and paraffin coating is used instead, in which case the wax on the inoculation hole should be pried off; be careful when peeling off the tape to avoid tearing the spawn bag.

5. Spawn bag quality standards. Under normal conditions, at 50-60d after inoculation, the mycelium can basically fill the bag, and with continued cultivation, the mycelium gradually thickens, and white mycelial membrane may form in some areas, followed by the culture medium surface beginning to wrinkle and shrink slightly, and secreting a pale yellow liquid. The spawn bag is basically mature and can be moved to the mushroom shed for color conversion, soil covering, and the next stage of management work.

VII. Bag Removal, Color Conversion, and Soil Covering

1. Bag removal. Soil-covered ground-cultivated shiitake mushrooms require spawn bag cultivation for 90d-110d before the spawn bags are basically mature and bag removal can be carried out. Use a sharp blade to cut the plastic of the spawn bag, first peel off both ends of the spawn bag, then peel off the spawn bag, and immediately arrange them flat on the bed surface.

2. Mushroom bed disinfection. After cleaning the mushroom bed and rinsing it with water, spray the bed surface with 6Kg bleaching powder or 50Kg lime water per thousand bags for 2-3d, then spray about 2Kg copper sulfate on the bed surface, cover with plastic film, disinfect for 3d, then remove the film, spread a 2cm sand layer on the bed surface, mix 1 bottle of chlordane and 2.5Kg formaldehyde with 70Kg water and sprinkle on the bed surface, then cover with film for 3 days; after removing the film, mix 0.5Kg potassium permanganate with 70Kg water and sprinkle on the bed surface, then spread a layer of lime before arranging the logs.

3. Color conversion. After arranging the spawn bags on the bed surface, immediately cover with plastic film, so that bag removal, log arrangement, and film covering are done simultaneously. After covering with film for 3 days, the film must be completely removed on the 4th day. If contaminating microorganisms are found at this time, promptly clean and treat them, sprinkle lime powder and cover with film. On the 5th day, strengthen ventilation once in the morning and once in the evening, for half an hour to 1 hour each, and rinse the spawn logs with clean water, combining with the prevention and treatment of contaminating microorganisms to allow color conversion.

4. Soil covering of spawn logs. The soil covering the spawn logs must be sandy subsoil selected from below 30cm of topsoil, and the excavated subsoil should be exposed to the scorching sun for 2d, sieved to remove stones and debris, and mixed with 10% lime powder or burnt soil and plant ash. When the spawn logs have converted color by 80-90%, stop watering for 4-5 days, fill in the prepared covering soil, press slightly to compact, until the spawn log surface is covered by 3cm, so that the spawn logs are completely covered. Do not cover with film during the day, cover with film at night, increase the frequency of watering, water regardless of sunny or rainy days, channel flowing stream water or mountain spring water or reservoir water into the field furrows, preferably change once a day; at this time, cover with film on rainy days, do not cover with film on sunny days.

VIII. Fruiting Management

1. Mushroom induction. After the spawn logs go through the watering management of the color conversion period, stop watering for 4-5d, then use the alternating wet and dry method to induce mushrooms, or pour water from a height onto the spawn log surface 2-3 times, which can produce a large number of small mushrooms. Do not use vibration to induce mushrooms unless absolutely necessary. To protect the spawn logs and promote high-quality mushroom production, excess mushroom buds must be thinned out.

2. Early-stage management. Soil-covered ground-cultivated shiitake mushrooms are mostly used for off-season cultivation to fill the summer fresh shiitake market demand. The first batch of mushrooms after bag removal generally occurs in early to mid-May to June, when temperature rises from low to high, but nighttime temperatures are relatively low, with large temperature differences between day and night, and it is also the rainy season with high humidity, which is favorable for fruiting body differentiation and pinning. As temperatures gradually rise, ventilation should be strengthened, generally hanging the film high so that rainwater does not fall on the spawn logs. After the first batch of shiitake mushrooms is harvested, drain the furrow water and stop watering to reduce the humidity of the mushroom bed, allowing the spawn log mycelium to resume growth and accumulate nutrients. Wait until the mycelium at the mushroom harvesting marks (depressions) has resumed growing white, then refill the furrow water and strengthen watering stimulation to promote the rapid pinning and formation of the next batch of fruiting bodies.

3. Mid-stage management. This period is from late June to late July, the hottest season of the year, with fewer mushrooms produced. Currently, soil-covered ground-cultivated shiitake mushrooms in our county rely on natural temperature combined with artificial regulation. Mid-stage management mainly involves lowering the temperature of the mushroom bed to promote fruiting body development, generally channeling mountain spring water or reservoir water to increase flow, increasing ventilation to lower temperature, and preventing high temperatures from burning the spawn logs.

4. Late-stage management. This period is from late August to the end of September, after the hot summer, temperatures have somewhat decreased. The spawn logs have consumed nutrients from early and mid-stage fruiting, and the shiitake mushroom spawn log mycelium is not as vigorous as in the early stage. Therefore, spawn log management at this stage should focus on preventing log rot and mushroom rot. If contaminating microorganisms are found, apply 5% cresol soap solution or 100-fold carbendazim to the affected area, and the next day apply 5% lime water, and move the diseased spawn logs elsewhere for centralized isolated management to prevent contagion.

IX. Harvesting

According to international market demand, the harvesting standard for fresh-keeping soil-covered ground-cultivated shiitake mushrooms is generally higher than that for dehydrated mushrooms. Generally, shiitake mushrooms should be harvested when the cap is about 50% open and the partial veil has not yet completely ruptured, and the scales on the cap should be preserved as much as possible, with no scuff marks on the cap. When packaging, prevent sawdust or other debris from falling on the gill area, and maintain the clean appearance of fresh mushrooms.

X. Pest and Disease Control

1. Control principles. Adhere to the principle of prevention first and integrated control, strictly controlling chemical pesticide control.

2. Main disease control. The main diseases include molds (Trichoderma, Neurospora, Penicillium, Mucor, Rhizopus) and bacteria and viruses. Prevention methods are: maintain a clean and hygienic environment, promptly remove diseases when found and carry out harmless treatment, and prohibit the use of chemical pesticides during the fruiting period.

3. Main pest control. The main pests include Oomorphoides cupreatus, Apriona germari, Photinus sp., Nemapogon granella, Odontotermes formosanus, slugs, and nematodes. Control methods: barrier method to prevent pests, dig trenches around the mushroom farm, and use shade nets around and above the mushroom shed to prevent pests from flying in. Prohibit the use of chemical pesticides during the fruiting period.