Fertilization Knowledge (Part 1)

Fertilizer is food for crops. There are now more than 20 known nutrients needed for crop growth. Among them, carbon, hydrogen, and oxygen can be obtained from air and water, and generally do not need to be provided in the form of fertilizers. Nitrogen, phosphorus, and potassium have higher contents in crops and are absorbed more, accounting for several percent to several thousandths of the weight of dry matter. They are called "macroelements". Nitrogen, phosphorus, and potassium are generally less abundant in soil and need to be supplemented in the form of fertilizers, so they are specifically called the "three elements of fertilizers." Calcium, magnesium and sulfur are generally called "middle elements". Elements such as copper, zinc, iron, manganese, boron, and molybdenum are required by crops in small amounts and are called "trace elements." Generally, the medium and trace elements contained in soil can meet the needs of crops. However, for some crops that are particularly sensitive to medium and trace elements and soils with serious trace element deficiencies, corresponding medium and trace element fertilizers must be applied.