These are the nutrients most essential to plant development:
Nitrogen is often required in the largest quantity by plants. It necessary for production of chlorophyll (the green pigment in plants responsible for photosynthesis) and for protein synthesis. A deficiency of nitrogen causes plants to develop yellow or pale leaves, and to have stunted growth.
Phosphorus rarely contributes significantly to the growth of plants, but is fundamental to the development of the crops. It is a vital component of adenosine triphosphate, which supplies energy for many processes in the plant. A lack of phosphorus can result in lower yields.
Potassium is needed by almost all crops, and often in higher rates than nitrogen. It regulates the plant’s water content and expansion.
Information from Yara.