Describe the various steps and processes involved in the nitrogen cycle. Also,explain the cycling of nitrogenous compounds in this cycle.

(N/A) $(i)$ Nitrogen fixation: It is the conversion of atmospheric nitrogen into water-soluble compounds (nitrates and nitrites) either by free-living bacteria or by $Rhizobium$ bacteria,which are found in the roots of legumes in special structures called root nodules. Atmospheric nitrogen also gets converted into nitrates and nitrites during lightning.
$(ii)$ Ammonification: The death and decay of plant bodies release ammonia. Animals excrete ammonia,urea,and uric acid as waste products. These nitrogenous compounds are converted into ammonia by putrefying bacteria,and this process is known as ammonification.
$(iii)$ Nitrification: Ammonia is converted first into nitrites and then into nitrates by nitrifying bacteria; this process is called nitrification. Plants generally take up nitrates and nitrites and convert them into amino acids,which are used to synthesize proteins.
$(iv)$ Denitrification: When plants or animals die,bacteria in the soil convert various nitrogenous compounds back into nitrates and nitrites. $A$ different type of bacteria,such as $Pseudomonas$,converts these nitrates and nitrites back into elemental nitrogen gas. This process is called denitrification. In this way,the cycle repeats continuously.