Do not use cottonseed hulls with a high content of cottonseed kernels directly for cultivating oyster mushrooms

Cottonseed hulls consist of the hulls left after the kernels are removed from cottonseed, the short cotton lint attached to the hulls, and a small amount of broken cottonseed kernels. Cottonseed hulls are rich in nitrogen, phosphorus, potassium, cellulose and lignin, with a carbon-to-nitrogen ratio of 79-85:1, are slightly alkaline, loose outside and dense inside, have good air permeability and strong water retention, and are a top-grade material for edible mushroom cultivation. However, cottonseed hulls contain toxic substances, and after sterilization under high pressure or normal pressure they release aldehydes, ketones and acids, and these toxic substances inhibit mycelial growth, delay pinning, and cause undesirable outcomes such as small mushrooms and poor mushroom quality. In particular, when the content of cottonseed kernels in the hulls is too high, mycelial colonization is severely affected, because cottonseed kernels contain gossypol, which inhibits mycelial growth when its content exceeds 3% and can stop mycelial growth when it reaches 5%. When using cottonseed hulls to cultivate edible mushrooms, the content of cottonseed kernels must not be too high and the cotton lint should not be too long; when there are too many broken cottonseed kernels, they should be sifted out before use; moreover, the cottonseed hulls must be fresh, with a grayish-white or snow-white color being best; the cottonseed hulls should be sun-dried under strong sunlight for 1-2 days, sprayed with dichlorvos, and piled and covered for 1-2 days before use. If cottonseed hulls are used for raw-material cultivation of oyster mushrooms, they need to be fermented in advance so that the pile temperature reaches above 65°C, and fermented for 4-5 days; this can kill pathogens and insect eggs in the material and decompose and release free gossypol.