COS is chitosanpro liquid. It is a kind of functional liquid for crop protection. With 100% molecule weight within 500Da, the material can enter into crop body directly. It can be used as nature fungicide.It has the advantages of high efficiency, environmental friendliness, and no side effects, and is widely used in agriculture and food industry. Meanwhile, as a kind of organic fertilizer, it has the effect of root promoting, crop growth regulation effects, etc.,