However, plants must take up various minerals through their root systems for use. Nitrogen, Potassium, and Phosphorous are obtained from the soil and are the primary macronutrients . Calcium, Magnesium, and Sulfur are the secondary macronutrients needed in lesser quantity. The micronutrients , needed in very small quantities and toxic in large quantities, include Iron, Manganese, Copper, Zinc, Boron, and Chlorine. A complete fertilizer provides all three primary macronutrients and some of the secondary and micronutrients.
Fertile soil contains the nutrients in a readily available form that plants require for growth.
The roots of the plant act as miners moving through the soil and bringing needed minerals into the plant roots. Structure of soil, indicating presence of bacteria, inorganic, and organic matter, water, and air. Image from Purves et al. However, the nitrogen in the atmosphere is not in a form that plants can utilize. These plants tend to have root nodules in which the nitrogen-fixing bacteria live.