The three steps of the nitrogen cycle in order, starting with nitrogen gas in the atmosphere, are what?
1. Nitrogen fixation: Nitrogen gas in the atmosphere is converted into ammonia by nitrogen-fixing bacteria.
2. Nitrification: Ammonia is converted into nitrites and nitrates by nitrifying bacteria.
3. Denitrification: Nitrates are converted back into nitrogen gas by denitrifying bacteria, completing the cycle.