Explanation

Nitrogen fixation is the process that changes nitrogen gas from the air into forms plants can use. Special bacteria in soil and plant roots perform this important task. These bacteria convert nitrogen gas into ammonia that plants can absorb through their roots.

The air around us is 78% nitrogen gas, but plants cannot use it directly. Only nitrogen-fixing bacteria have the special enzymes needed for this conversion. Some of these bacteria live in bumps on legume roots like beans and peas.

Nitrification converts ammonia into nitrates, which happens after nitrogen fixation. Denitrification returns nitrogen back to the atmosphere. Ammonification breaks down dead organisms to release ammonia. Only nitrogen fixation brings nitrogen from air into a usable form.