The nutritional value of various elements

Regardless of the quantity needed, each plant nutrient fulfills a specific role in plant growth and food production. Nutrients cannot be substituted for one another.
Nitrogen (N)
N is a constituent of the building blocks of almost all plant structures. It is an essential component of chlorophyll, enzymes, proteins, etc. Rather high amounts of nitrogen are required compared to other essential nutrients. It stimulates root growth and crop development as well as uptake of other nutrients. Therefore, plants, except for legumes which fix N from the air, usually respond quickly to N fertilization. N is taken up from the soil in the form of nitrate or ammonium.
Phosphorus (P)
P plays a key role in the transfer of energy, thus making it essential for photosynthesis and other physiological processes in the plant. It is indispensable for cell differentiation and for the development of the tissues that form the growing points of the plants.
Potassium (K)
K activates more than 60 enzymes, thus playing a vital part in carbohydrate and protein synthesis. It improves the water use of the plant and increases tolerance to stresses such as drought, frost, salinity and diseases.
Sulphur (S)
S is an essential constituent of protein and is also involved in the formation of chlorophyll. Until recently its role as a plant nutrient was often underestimated because S deposition from industrial emissions provided what was essentially free S fertilization.
Magnesium (Mg)
Mg is the central constituent of chlorophyll, the green pigment that plants use to convert the sun’s energy into carbohydrates. Mg is also involved in enzyme reactions related to the energy transfer of the plant.
Calcium (Ca)
Ca is essential for root growth and as a constituent of cell walls. Though most soils contain sufficient plant-available calcium, deficiency may occur on tropical soils. However, the aim of calcium application (liming) is usually to limit or reduce soil acidity.
Micronutrients are important for a variety of vital plant functions. These affect both yield and quality traits. Low micronutrient concentrations at planting can also reduce seed vigour, and affect biological N fixation, among others.

Plants and people both need nutrients

The nutrients in plants ensure that enough quality food can be grown, but those nutrients often fulfill important functions for human health as well, some of which are very distinct from the way plants use the same nutrients. For example, all higher animals require phosphorus for the development of healthy, strong bones.