In the nitrogen cycle, how does nitrogen get in the soil?
In the atmosphere, nitrogen is present in its elemental form. Plants cannot utilize elemental Nitrogen.
Nitrogen fixing bacteria present in the soil like Rhizobium etc. convert the atmospheric nitrogen into nitrates or nitries and will fix it into the soil. Thus makes the soil fertile. These nitrites or nitrates will be utilized by the plants for their growth.
These nitrogen fixing bacteria are found in the root nodules of Leguminacea plants also.
In this way atmospheric nitrogen is fixed into the soil.