Legumes, a type of plant in the Fabacae family, are symbionts to some of these microbes that fix N2.
NH3 is a building block to Amino acids and proteins amongst other things essential for life.
However, just over half of all reactive nitrogen entering the biosphere is attributable to anthropogenic activity such as industrial fertilizer production.
As a consequence, an excess of Nr can affect the environment relatively quickly.
This also means that nitrogen-related problems need to be looked at in an integrated manner.