Plants, Nutrients and Australian Soils

Dinitrogen [N₂] is the most abundant gas in the atmosphere comprising 78% of the air we breathe. Despite its abundance on earth only a minute fraction of total global nitrogen occurs in a chemical form that is available to plants. The two main sources of inorganic nitrogen used by plants are nitrate (NO₃^-) and ammonium (NH₄⁺).

Nitrogen is required by plants in relatively large amounts for the synthesis of proteins, nucleic acids and numerous other simple and complex organic compounds. In herbaceous plants, it may comprise 2 to 5% of the total plant dry weight.

A satisfactory nitrogen supply is therefore essential for plant growth, and low availability of nitrogen in soils frequently limits the growth of agricultural crops and may limit the productivity of native plant communities.