The three categories of plant nutrients are primary nutrients, secondary nutrients, and micronutrients.
The primary plant nutrients are nitrogen (N), phosphorus (P), and potassium (K). These essential elements are required by plants in higher quantities than elements that fall into the other two categories.
Secondary plant nutrients are calcium (Ca), magnesium (Mg), and sulphur (S). These elements, although not needed in such high quantities, are necessary for plant health.
Last, but not least, there are plant micronutrients. These are needed in much smaller quantities than other plant nutrients, but are just as necessary for growth and development. The plant micronutrients are boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn). All of these micronutrients aid in many different roles in plant biology.
Plants can receive nutrients from the soil, fertilizers, or through individual nutrient application. For example, to increase plant flowering and fruiting, gardeners can use PK Boosters to give plants more phosphorus and potassium; both of which are essential to fruit/flower growth and development.