The Complete Nitrogen Cycle

Ever wondered how plants get nitrogen when they can't just breathe it in like oxygen? The nitrogen cycle is nature's brilliant solution to converting unusable nitrogen gas into forms that living things can actually absorb and use.

Nitrogen fixation kicks off the whole process by converting atmospheric nitrogen gas (N₂) into ammonia (NH₃). This happens under anaerobic conditions thanks to nitrogen-fixing bacteria like Azotobacter and Rhizobium. These bacteria are absolute heroes because they're doing chemistry that would normally require massive industrial processes.

Once ammonia is produced, nitrification takes over in aerobic conditions. Nitrosomonas bacteria convert ammonia to nitrite ions (NO₂⁻), then Nitrobacteria convert these to nitrate ions (NO₃⁻). Plants absorb these nitrates through their roots using active transport and facilitated diffusion - this process is called assimilation.

The cycle completes with ammonification (also called putrefaction) and denitrification. During decomposition, proteins break down into amino acids, then deaminases remove NH₂ groups to release ammonia back into the soil. Finally, Pseudomonas bacteria convert nitrates back to nitrogen gas under anaerobic conditions, returning nitrogen to the atmosphere.

Quick Tip: Remember the cycle as "Fix → Nitrify → Assimilate → Decompose → Denitrify" - it flows in a logical sequence that you can easily memorise for exams.