What conditions are needed for the growth and development of straw mushrooms?
1. Nutrition
Straw mushroom is a saprophytic fungus that does not contain chlorophyll and cannot carry out photosynthesis to synthesize the nutrients it needs, so these must be supplied from outside.
The nutrients required by straw mushroom are mainly carbohydrates and nitrogen-containing compounds. Carbohydrates mainly include sugars such as glucose, sucrose, maltose, starch, hemicellulose and cellulose. Organic nitrogen compounds mainly include peptone, amino acids and urea; inorganic nitrogen compounds include ammonium sulfate and ammonium nitrate. It is generally considered that a carbon-to-nitrogen ratio (C/N) of 20:1 is suitable for the vegetative growth stage, and a carbon-to-nitrogen ratio (C/N) of 30:1 to 40:1 is better for the reproductive growth stage. In addition to carbon and nitrogen sources, various mineral elements such as potassium, magnesium, sulfur, phosphorus and calcium are also necessary. In addition, a certain amount of vitamins is also needed, especially vitamin B1. Rice straw, wheat straw, waste cotton, cottonseed hulls, sugarcane bagasse and so on all contain large amounts of carbon, nitrogen, inorganic salts and other nutrients.
2. Temperature
Straw mushroom is a high-temperature edible fungus, with a growth and development temperature of 10 to 45°C. The suitable temperature differs among different growth stages. The temperature for spore germination is 25 to 45°C, with the optimum temperature being 40°C. At 30°C, the spore germination rate does not exceed 20%, while below 25°C or above 45°C, germination does not occur. The temperature for mycelial growth is 10 to 43°C, with the suitable temperature being 30 to 39°C and the optimum temperature being 36°C; below 15°C or above 42°C, mycelial growth is strongly inhibited. Mycelium will die after being kept below 5°C or above 45°C for a long time. The optimum air temperature for fruiting body differentiation and development is 27 to 31°C. When the average temperature is below 23°C, fruiting bodies are difficult to form. The optimum temperature for fruiting body growth is 28 to 33°C, and below 21°C or above 45°C, young mushroom buds die.
3. Moisture
Moisture is a prerequisite for the growth and development of straw mushroom. Straw mushroom is a fungus that prefers warmth and moisture, and its moisture requirements are higher than those of other artificially cultivated fungi. The water content of the straw mushroom substrate is generally required to be 70% to 75%; during the mycelial growth stage, the relative air humidity is required to be 80%, and during the fruiting body growth stage it is about 90%. In production, if moisture is insufficient, mycelial growth is slow, fruiting bodies are difficult to form, and they may even die; if there is too much water, then aeration is poor, respiration is affected, and mushroom rot and mushroom death are caused. When the temperature is too low or too high, the water content of the substrate should be appropriately reduced.
4. Oxygen
Straw mushroom is an aerobic fungus and needs to take in oxygen and release carbon dioxide during respiration. When the carbon dioxide concentration in the substrate and in the air near its surface reaches or exceeds 0.5%, it inhibits mycelial growth and fruiting body formation. Therefore, a certain amount of fresh air must be ensured to enter the straw mushroom cultivation room, but if the ventilation volume is too large, the water content in the substrate is easily lost. In case of high temperature (mushroom room temperature exceeding 35°C), the ventilation volume of the cultivation room should be increased.
5. Light
The germination of straw mushroom basidiospores and the growth and development of mycelium do not require light, and direct light hinders mycelial growth; a certain amount of scattered light (light intensity of several hundred lux, that is, normal vision can distinguish newspaper text in the mushroom room) has a good effect on fruiting body formation. At the same time, the intensity of light also affects the color and quality of the fruiting bodies. When light is strong, the fruiting bodies are dark in color and glossy, and the fruiting body tissue is dense; when light is insufficient, the fruiting bodies are grayish white; when there is no light, the fruiting bodies are white.
6. pH
For the germination of straw mushroom basidiospores, the suitable pH is 6 to 7.5. Under the condition of pH 7.5, the spore germination rate is the highest; when pH exceeds 7.5, the germination rate drops sharply; at pH 8.0, the spore germination rate is almost equal to zero. Straw mushroom mycelium has a relatively broad adaptability to pH and can grow within the range of pH 4 to 10.3. When mixing the substrate, pH 7.5 to 8 is suitable.