There are 17 essential elements, but not all of those are required as fertilizer. The primary nutrients, macronutrients, secondary nutrients, and micronutrients will be explained, not much in terms of function, but in terms of how the turf manager should think about adjusting their supply. The primary elements are never applied as fertilizer because the grass gets them from air and water. Of the macronutrients, those most often required as fertilizer are nitrogen and potassium. Secondary nutrients and micronutrients are rarely required by the grass, but are sometimes applied to ensure they are present in adequate amounts.