There are numerous building blocks of life that plants need for healthy and optimum growth. Without these nutrients, plants cannot grow to their full potential, will provide lower yields, and be more susceptible to disease.
The three most important nutrients, without any one of which plants could not survive, are referred to as the primary macronutrients: Nitrogen (N), Phosphorus (P), and Potassium (K).
Soils often lack these nutrients, either naturally, or as a result of over-cultivation or other environmental factors. In cases where soils are lacking, nutrients must be put back into the soil in order to create the ideal environment for optimal plant growth.