Question

Atmospheric nitrogen is converted to usable forms like nitrites and nitrates by the process of ______ .

• A. ammonification
• B. denitrification
• C. nitrification
• D. nitrogen fixation

Answer 1

The correct option is D nitrogen fixation

Plants can not take up nitrogen directly from the atmosphere. So, the nitrogen is converted to usable forms in the followings ways:

$\bullet$ Certain nitrogen fixing bacteria like Azotobacter, Rhizobium, Cyanobacteria, etc., convert nitrogen molecule into nitrates and nitrites, which can be taken up by plants.

$\bullet$ During lightning, the nitrogen is fixed by the atmosphere. Due to high temperatures and pressure, nitrogen is converted to the oxides of nitrogen which dissolves in water to give nitric and nitrous acids which fall onto the ground and is used up by plants.