Detailed Explanation of Points to Note When Mixing Substrate for Substitute-Material Cultivation of Shiitake Mushrooms

Substitute-material cultivation of shiitake mushrooms is another cultivation method following log or round-wood cultivation. Its cultivation forms are diverse, mainly designed according to differences in cultivation conditions, cultivation materials and cultivation containers. It has developed rapidly in recent years and now accounts for more than 95% of the cultivation area. In its medium, materials rich in cellulose, lignin and hemicellulose, such as wood chips, crop straw and wild grasses, are used as the main components of the cultivation material, appropriately supplemented with auxiliary materials such as wheat bran and rice bran rich in organic matter and vitamins, as well as gypsum, calcium carbonate and similar substances containing inorganic salts. The water content is adjusted to around 60%, and after sterilization it is inoculated and cultivated.

The preparation of the culture substrate is an important step in shiitake mushroom production. Mistakes in substrate preparation often cause acid spoilage of the substrate, contamination by competing microorganisms, and a decline in the finished-product rate. Although in some cases the mycelium can still slowly grow to the bottom of the bag, the mycelium is not robust, fruiting is late, and yield is extremely low, affecting economic returns. The following issues should be noted during substrate preparation.

1. Site: The site for mixing materials and filling bags is best treated with cement and have a 1% slope so that washing water can drain away naturally. After daily operations, rinse with clean water and sweep up and discard leftover culture substrate so it is no longer used, to prevent microorganisms in the leftover material from entering the newly mixed substrate, which would accelerate the rate of substrate acid spoilage and increase the chance of contamination.

2. Sterilization: The culture substrate should be mixed, bagged and sterilized in sequence. No more than 4 hours may pass from mixing to sterilization. When loading the substrate into the sterilizer for sterilization, use a strong fire to raise the temperature so that the substrate enters a sterile state as early as possible.

3. Water adjustment: Because raw materials differ in water content and physical properties, and because the air temperature and relative humidity during mixing differ, water adjustment must be handled flexibly. When the substrate is on the dry side, the particles are fine, and acidity is strong, the water can be adjusted somewhat higher; when the substrate has a higher water content, the particles are coarse and hard, and water absorption is poor, the water should be adjusted lower. On sunny days, when bagging takes a long time, adjust the water somewhat higher or adjust it once more in between; on cloudy days, when relative air humidity is high and water does not evaporate easily, adjust the water somewhat lower. Raw materials such as sugarcane bagasse, corncobs and cottonseed hulls have loose, large particles and absorb water easily, so the amount of water added should be appropriately increased.

4. Even mixing: Make every effort to mix the materials evenly. When mixing is uneven, some fungus bags fail to fruit or fruit late, and some have very poor yield and quality. This is mainly due to an uneven carbon-to-nitrogen ratio. In mixing, all raw materials should first be mixed dry, then mixed wet, so that the main raw materials and auxiliary materials are mixed evenly, the water and culture substrate are mixed evenly, and the pH is uniform.

5. Bagging time: When the temperature is on the high side, the time for mixing and bagging must not be too long. It is required to organize manpower and race against time to finish, in order to prevent acid spoilage of the culture substrate and loss of nutrients. 6. Aseptic bagging: In substrate preparation, to avoid contamination, on the basis of selecting good raw materials, choose a sunny morning for mixing, and strive to complete loading in the cooler morning and enter the sterile procedure, reducing the chance of contamination by competing microorganisms.