Secondary Macronutrients–calcium, magnesium and sulfur–are essential for plants' metabolic processes, but are not needed in as high amounts as the primary macronutrients, N-P-K.
Plants also require smaller amounts of certain trace minerals, or micronutrients, boron, chlorine, copper, iron, manganese, molybdenum and zinc. These minerals are needed in very small amounts and additions to your soil should be guided by a professional soil test. In addition, these minerals must be transformed by soil microbes to their basic form to be available for the plant to use. Shop soil inoculants for products that will boost your soil biology and help plants use the nutrients in the soil.