Nitrogen is also a key element that makes up DNA and proteins. It is present in its cycle in various forms including nitrogen gas which makes up the biggest part of the air in the Earth’s atmosphere, ammonia, nitrites and nitrates in the soil, and of course in all the waste products of living things.
Microorganisms also play a key role here in decomposing these materials and producing the intermediary nitrates. Following a series of reactions, nitrogen from these sources ends up back into the atmosphere.
In the nitrogen cycle there are two stages of N presence: the atmosphere and the ground. Whenever N is in the atmosphere it’s in the form of nitrogen gas, N2 which of course is what most of the air is made of. In the ground, N is found in ammonia (NH3), nitrite (NO2-) and nitrate (NO3-).
Find it hard to distinguish the formulae for nitrite and nitrate? Needn’t be! A is large (3-) and i is little (2-), former’s nitrate, latter nitrite…