Fishing and Guano birds assist the cycling of

The process of reducing nitrate to gaseous nitrogen is known as:

One of the ways in which the nitrogen of the atmosphere is converted into nitrate for plants is by the action of

Nitrifying bacteria:

Which two distinct microbial processes are responsible for the release of fixed nitrogen as dinitrogen gas $(N_2)$ to the atmosphere?

Reaction carried out by $N_{2}$ metabolising microbes include:
$I.$ $2 NH_{3} + 3 O_{2} \rightarrow 2 NO_{2}^{-} + 2 H^{+} + 2 H_{2} O$
$II.$ $2 NO_{2}^{-} + O_{2} \rightarrow 2 NO_{3}^{-}$
Which of the following statements about these equations is not true?