Nitrogen is an integral component of all amino acids, which are the building blocks of all proteins, including the enzymes. Nitrogen is also a component of nucleic acids (the seat of genetic inheritance), and chlorophyll. Nitrogen is essential for carbohydrate use within plants. A good supply of nitrogen stimulates root growth and development, and uptake of other nutrients.

The most important source of nitrogen is the atmosphere which contains 78% of nitrogen as an inert gas (N2). In the inert phase, nitrogen cannot be used by plants and it has to be converted to forms usable by plants through mineralization. Nitrogen is absorbed by plants in mineral (inorganic) forms, i.e., as nitrate and ammonium ions.