Fishing and Guano birds assist the cycling of

Decomposition of organic nitrogen of dead plants and animals into ammonia is called.

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

$A$: Ammonia is oxidized first to nitrite and then to nitrate by the action of $Nitrosomonas$ and $Nitrobacter$ respectively.
$R$: Nitrite thus formed is absorbed by leaves.

Which bacteria are responsible for the conversion of ammonia into nitrite ions and nitrite into nitrate ions,respectively?

Nitrates of soil are also leached deep into the Earth by . . . . . . .