The appearance of ferrous sulfate is a blue-green monoclinic crystal, so it is generally called "green manure" in agriculture. Ferrous sulfate is mainly used in agriculture to adjust the pH of the soil, promote the formation of chlorophyll, and prevent yellowing disease caused by iron deficiency in flowers and trees. It is an indispensable element for acid-loving flowers and trees, especially iron trees. Ferrous sulfate contains 19-20% iron. It is a good iron fertilizer, suitable for acid-loving plants, and can be used frequently to prevent and treat yellowing disease. Iron is necessary for the formation of chlorophyll in plants. When iron is deficient, the formation of chlorophyll is blocked, causing plants to suffer from chlorosis, and the leaves turn pale yellow. The aqueous solution of ferrous sulfate can directly provide iron that can be absorbed and utilized by plants, and can reduce the alkalinity of the soil. The application of ferrous sulfate, generally speaking, if the potting soil is directly watered with a 0.2%-0.5% solution, there will be a certain effect, but due to the soluble iron in the poured soil, it will quickly be fixed into an insoluble iron-containing compound It fails. Therefore, in order to avoid the loss of iron elements, 0.2-0.3% ferrous sulfate solution can be used to spray the plants on the foliage.