2. Micro-fertilizers are mainly inorganic salts and oxides. Most of them are by-products or wastes from mining and metallurgy. Can be used for preparing multi-element foliar fertilizer for fruit trees, foliar fertilizer for vegetables and compound fertilizer.
3. Plants need 16 elements for growth and development, but the demand is quite different. Traditionally, carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulfur are called macro elements. The other seven elements with less requirements and contents below 0.0 1% are called trace elements. Micro-fertilizer is the abbreviation of trace element fertilizer. Compared with a large number of elements, it mainly includes iron, zinc, copper, manganese, boron and molybdenum. Traditionally, inorganic salts are used to supplement trace elements such as iron, zinc and manganese, such as zinc sulfate, ferrous sulfate and manganese sulfate, but there are many problems (for example, ferrous sulfate is easily converted into trivalent iron under natural conditions, and zinc sulfate and manganese sulfate are easily lost), so the application range is narrow and the efficiency is low, which is not conducive to crop absorption. Moreover, due to the alkaline reaction and redox reaction of the soil itself, insoluble hydroxides are formed, and so on.