Key Cultivation Techniques for Converting a Cold Storage Facility into a Mushroom Farm
Cold storage facilities have good insulation and moisture retention, with easily controlled temperature and humidity and weak light, making them quite suitable for mushroom growth and development conditions. With slight modifications to the existing facilities inside the storage, year-round mushroom production can be achieved, with 3 cultivation cycles possible per year.
1 Cold storage conversion
Cold storage can be divided by temperature into high-temperature storage (fruit cold storage) and low-temperature storage (meat and aquatic product storage); by construction location, it can be divided into above-ground storage and cave storage. These cold storage facilities were originally designed and built for storing fruits and vegetables, and their performance is not quite suitable for mushroom cultivation, so appropriate modifications must be made to meet the environmental conditions for mushroom growth and development. Production practice has proven that high-temperature storage is easier to utilize than low-temperature storage, small storage is easier to utilize than large storage, and above-ground storage is easier to utilize than cave storage. From the perspective of industrial year-round cultivation, cold storage clusters are easier to utilize than single storage units. If the refrigeration equipment of the cold storage is in good condition, it is still necessary to modify or add bed frames, ventilation, heating, water supply and other conditions.
1.1 Bed frame specifications. Cold storage generally has bed frames for placing goods, which can be converted into 5-tier mushroom beds with a total height of 3.5 m. The bed frame specifications are: frame width 1.2 m, layer spacing 60 cm, top layer 1.2 m from the roof, bottom layer 20 cm from the ground, with aisles of no less than 50 cm width between bed frames. If the cold storage has a floor area of 200 sq m, the mushroom bed area with 5-tier bed frames is approximately 500 sq m.
1.2 Ventilation facilities. During summer production, to avoid directly drawing hot and humid outside air into the cold storage, the air inlet duct can be connected to the air inlet of the refrigeration unit inside the storage, so that the refrigeration unit can both directly cool fresh air and circulate and cool indoor air. The motor power of the original refrigeration unit, circulation fan and exhaust outlet inside the storage remains unchanged.
1.3 Heating equipment. Install a 0.75-ton steam boiler outside the storage, using both radiator fins and air release valves for heating, to carry out post-fermentation of the culture material.
1.4 Install water pipes to facilitate spraying and humidification.
2 Cultivation operations
2.1 Strain selection. Through multiple trials and comparisons, the mushroom strain "Heda No. 2" suitable for cultivation in cold storage was selected. This strain has fast mycelial growth, uniform fruiting, quick flushing, high yield and high marketability rate.
2.2 Culture material formula calculated per 100 sq m of fruiting area: wheat straw 4500 kg, wet chicken manure 4000 kg (about 4 cubic meters), cake fertilizer 90 kg, gypsum 350 kg, urea 30 kg, lime 140 kg, phosphate fertilizer 90 kg.
The characteristics of this formula: First, the nitrogen content is relatively high, reaching about 2.4% after post-fermentation; second, the gypsum dosage exceeds the conventional amount (generally 2%), because fresh chicken manure is relatively sticky (containing about 50% moisture), and adding more gypsum can improve the dispersibility of the compost.
2.3 Pre-fermentation. According to the formula, mix the pre-wetted straw, wet chicken manure and other auxiliary materials evenly and build a pile. The water adjustment principle is: wet on the first turn, adjust on the second, and do not touch on the third, meaning the first turning should add sufficient water, the second turning should appropriately supplement water, and the third turning should avoid adding water as much as possible. Pre-fermentation lasts about 21 days, avoiding over-fermentation of the culture material.
Qualified culture material standards after pre-fermentation: (1) Sensory standards: the material is brown, still elastic when tightly squeezed, sticky and dirty to the hands, the leachate is turbid, water is visible between the fingers but does not drip, there is an ammonia smell, and white spots of actinomycetes are visible; (2) Physicochemical standards: moisture content 72%-74%, pH 7.8-8.2, nitrogen content 1.8%-2%, ammonia content 0.4%.
2.4 Post-fermentation is a necessary procedure to increase yield and reduce pests and diseases. The operations are as follows.
While still hot, transport the pre-fermentation-qualified culture material into the storage, spread it loosely and evenly on each tier of shelves, install thermistor thermometers, placing 3 in the material and 2 in the air space. Raise the temperature through heating pipes or by directly releasing steam, while turning on fans for indoor air circulation. When the temperature rises to 58-60 degrees C, maintain for 6-8 hours for pasteurization.
Draw fresh air into the storage, slowly lower the temperature for decomposition and maturation. The indoor air temperature should preferably decrease by 3 degrees C per day. After 10 days in winter, 11 days in spring, and 12 days in summer, when the material temperature and air temperature stabilize at around 25 degrees C, end post-fermentation. During this period, to reduce the temperature and humidity differences between upper and lower material beds, indoor circulating air must be well managed.
Qualified culture material standards after post-fermentation: (1) Sensory standards: straw segments are brown, easily broken and lusterless, water marks appear between fingers when tightly squeezed, the leachate is not turbid, does not dirty the hands, has no ammonia smell, and white spots of actinomycetes are visible; (2) Physicochemical indicators: moisture content 65%-68%, pH 7.2-7.5, nitrogen content >=2%, ammonia content <=0.01%.
2.5 Spawning. Spawn rate 1 gram per cubic meter. Use the mixed spawning method, thoroughly mixing the spawn with the culture material. This method has many germination points, fast mycelial growth and uniform fruiting.
2.6 Casing soil. Peat soil is best for casing, but the cost is high. Through experimental screening, it was found that adding an appropriate amount of 15% power plant fly ash to clay soil produces a good casing effect. Fly ash has been through high temperatures, has few contaminating microorganisms, good air permeability, and does not compact. It holds more water, mycelium grows onto the soil quickly, and fruiting is early. Use the single casing method with a thickness of 3-3.5 cm. After casing, spray water for 3 days to bring the moisture content to saturation. Maintain the material temperature at 24-26 degrees C and relative humidity at 85%-90%. To promote mycelial growth onto the soil, ventilate for 3-5 hours daily.
3 Fruiting management
Using cold storage for mushroom cultivation differs greatly from dedicated mushroom houses in terms of temperature control, ventilation and humidification. Therefore, the techniques for regulating temperature, humidity and air during the fruiting period are quite critical. Some practical experience and monitoring data are presented below.
3.1 Cooling. Cooling is the most important and decisive factor in inducing mushroom primordium formation. When mycelium has grown onto 60% of the soil surface, cooling should be applied immediately, controlling the temperature at 15-16 degrees C to promote mushroom primordium formation. Temperature control depends on natural air temperature, and the temperature control and ventilation methods used differ across seasons.
For spring and autumn production, the temperature inside the storage is relatively suitable, and basically no energy is needed for cooling or heating. During the mycelial growth and fruiting periods, appropriately supply fresh air and circulating air to maintain suitable temperature and humidity.
During summer production, the refrigeration unit must be turned on once daily during the mycelial growth period, for about 1 hour each time, to maintain the temperature needed for mycelial growth. During the fruiting period, the refrigeration unit must be turned on twice daily, for 1-2 hours each time. Because the outside air temperature is hot and humid, fresh air intake is generally arranged in the morning and evening for 2-3 hours.
During winter production, heating is applied once every 2 days during the mycelial growth period, for 2-3 hours each time. During the fruiting period, heating once every 4-5 days is sufficient to maintain a storage temperature of 16-18 degrees C. Ventilation is carried out at noon each day when the temperature is relatively higher. Winter mushroom house temperature is relatively easier to control compared to summer, and management is easier.
3.2 When white primordia the size of rice grains form on the casing surface, lightly spray water daily, in small amounts but frequently. When young mushrooms grow to the size of soybeans, increase the amount of water sprayed. Thereafter, as the mushrooms gradually grow larger, spray more when there are many mushrooms and less when there are few. The amount of water sprayed can be calculated as 1 kg of water replenished per 1 kg of mushrooms produced. During peak harvest periods, generally do not spray water; after harvesting, spray one heavy watering to promote flushing. Always ventilate with fresh air or carry out indoor air circulation immediately after spraying water, to dissipate moisture on the mushroom bodies and prevent bacterial infection of the mushroom bodies.
3.3 Ventilation. Whether mushroom cultivation in cold storage succeeds depends most critically on solving the ventilation problem.
The theoretical concentration of carbon dioxide in the atmosphere outside cold storage is 0.03% (along with 78% nitrogen, 21% oxygen, and the remainder being argon, neon and other inert gases).
Inside cold storage, if ventilation is not carried out throughout the night during the mycelial growth period, the carbon dioxide concentration can reach as high as 2%, which is 50 times higher than outside. During the fruiting period, if the carbon dioxide concentration in the air exceeds 0.2%, it is harmful to mushroom development, for example causing poor development of young mushrooms, long stipes and easy cap opening, forming thin and light inferior mushrooms or deformed mushrooms. If the carbon dioxide concentration exceeds 0.6%, the mushroom beds easily develop "mycelial overgrowth," forming a dense mycelial mat without producing mushroom buds.
3.4 Water and humidity. Rapidly growing and developing mushrooms have strong transpiration. A mushroom with a diameter of 6 cm has a water evaporation rate of 2-4 mg/24 hours. If water evaporates too quickly, the mushroom surface will lose water, producing scales or cracking. Therefore, it is necessary to regularly spray "maintenance water" in mist form into the air space and onto the soil surface, so as to maintain the mushroom house air humidity and bed humidity within normal ranges, meeting the needs of mushroom growth and development. The amount of water sprayed should be flexibly controlled according to the requirements of mushroom development. Generally, during the mycelial growth period, mycelium maintenance period and flushing period, less water can be sprayed, every other day; during the fruiting period, more water should be sprayed, frequently. Especially during the fruiting period, spray 1-2 times daily. "Maintenance water" is the regular water used in mushroom house management; the amount used each time is not large, but its role is no less important than the "fruiting water" applied to the casing soil. When the air relative humidity approaches saturation (above 98%), condensation will appear on the mushroom surface, with a water film covering the mushroom surface, easily causing bacterial spot disease. To prevent this disease, ventilation and air circulation must be carried out simultaneously when spraying water. Note that in hot and humid summer, when hot and humid air is blown directly into a relatively cool mushroom house, water condensation will occur. Even with enhanced ventilation, the mushroom bodies will form a condensed water layer, leading to bacterial spots on the mushroom bodies or mold growth on the bed surface. This is the main reason for the high rate of contamination in mushroom houses in summer.
From May to June, the temperature outside the cold storage is 30-35 degrees C during the day and 25-30 degrees C at night; the outdoor humidity is 60% on clear days and 90% on rainy days. In a 130 sq m mushroom house, the circulating air cooler is run 3 times a day for cooling, 80-130 minutes each time, with temperature varying within a range of 4-5 degrees C and air relative humidity varying within a range of 30%-40%. The sudden drop in storage temperature causes loss of air moisture content, resulting in a sharp drop in humidity, which is the main reason for water loss from the beds and mushroom bodies, and even drying and death of young mushrooms. When using ordinary cold storage for cultivation, since there is no equipment for pre-heating or pre-cooling, humidifying or dehumidifying the air, generally only untreated natural air can be drawn in, so regulating air humidity is a difficult point. It should be pointed out that in summer, the air outside the storage is hot and humid, while the indoor walls and other environments are dry and cold. In this situation, when air is drawn in, condensation water will be produced, causing a sharp increase in humidity inside the storage and easily leading to outbreaks of red bread mold and other contaminating microorganisms.
When the air inside the storage is dry, use a humidifier or spray cooling, atomizing water into droplets of 3-30 micrometers. Because the water rapidly evaporates and absorbs a large amount of heat from the air, the moisture is then expelled outside to achieve cooling, with a cooling range of 3-5 degrees C.
3.5 Light. In June at 8 AM, outdoor sunlight is 80,000 lux, and in outdoor shade it is 660 lux; in a 130 sq m storage equipped with 36 60-watt fluorescent tubes, at 50 cm from the tubes it is 650 lux: at the upper, middle and lower mushroom shelves the averages are 123, 59 and 41 lux respectively. Such light intensity is sufficient for mushrooms (but far from meeting the requirements of white lingzhi mushroom).
3.6 Pest and disease control. In summer cultivation, cold storage is prone to outbreaks of pests and diseases. For example, mushroom cultivation requires high-temperature and high-humidity conditions (such as post-fermentation), and bed frames are mostly made of bamboo and wood, which are extremely prone to mold. Therefore, the mindset of "prevention first, integrated control" must be established, and comprehensive disinfection inside and outside the mushroom house must be carefully carried out. Generally, after fumigation with formaldehyde, spray with Bordeaux mixture, and preferably use high-temperature steam sterilization. In addition, pay attention to cleaning up all sources of contamination, which is the foundation of the entire control effort.