Why NPK in agriculture is called “three elements of fertilizer”?

Why NPK in agriculture is called “three elements of fertilizer”?
In the case of crops, although more than 90% of dry matter is composed of three elements: carbon, hydrogen, and oxygen, and the nutrients supplied by soil account for only 5% of the total amount, except in special cases (such as drought and flood years). In addition, the field crops will not reduce production due to lack of carbon, hydrogen and oxygen. On the contrary, the crops that affect the crop yield are often the small part of the soil supply, especially the N, P and K nutrient elements. Large, but most of the available N, P, and K nutrients in the soil are not abundant, and there is a significant gap between supply and demand. Agricultural practices have proven that in order to increase crop yield, it is often necessary to use chemical fertilizers to regulate the supply and demand of nutrients between soil and crops. Practice has proved that after applying nitrogen, phosphorus and potassium fertilizers, the crops often have obvious effect of increasing production. Therefore, people say that NPK is the "three elements of fertilizer." This is why the fertilizer industry in China has always attached great importance to the production of NPK fertilizers.

Organic Fertilizer:Corn Steep Liquor Powder 42%;Bacillus Subtilis;Seaweed Fertilizer;Potassium Fulvic Acid