Nitrogen Cycle
Movement of nitrogen among atmosphere, organisms, soils, and water through fixation, nitrification, and denitrification.
Formula
N2 → NH4⁺ (fixation) → NO3⁻ (nitrification) → N2 (denitrification)
Real World
The Haber-Bosch process, invented in 1913, now fixes roughly 150 million tonnes of nitrogen per year for fertiliser — more than all natural biological fixation combined, fundamentally altering the global nitrogen cycle.
Exam Focus
Learn the sequence fixation → nitrification → denitrification and name the bacterial genera (Rhizobium, Nitrosomonas, Nitrobacter) for top marks.
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