The correct process that represents ways nitrogen can enter the soil is III only which is rainfall.
Atmospheric nitrogen can not be used by most organisms due to fact that the three covalent bonds present in atmospheric nitrogen are very hard to break.
Nitrogen fixation takes place either:
- By the microbes and produce ammonia by biological nitrogen fixation. or,
- Rainstorms, natural lighting, rainfall contribute to atmospheric nitrogen into nitrates through raindrops that reach the soil.
- Nitrates are the most bio-available form of nitrogen.
Thus, the correct answer is - III only which is rainfall.
Learn more about nitrogen fixation:
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