The nitrogen cycle is how nitrogen moves through the air, soil, plants, animals, and back again. Even though about 78% of the air is nitrogen, people and animals can’t breathe it in or use it directly. We get nitrogen from the food we eat.
In nature, bacteria on plant roots and lightning help change nitrogen gas into a form called ammonia this step is called nitrogen fixation. Since ammonia is harmful, other bacteria change it into nitrites and then nitrates through a process called nitrification.
Plants take in nitrates from the soil to grow, and animals get nitrogen by eating plants. When animals go to the bathroom or die, decomposers break down the waste and dead material in a process called ammonification, which returns nitrogen to the soil. Some bacteria then change nitrates back into nitrogen gas in a process called denitrification, sending it into the air again.
This process keeps repeating, recycling nitrogen so all living things can use it to make proteins and DNA.
Key Processes:
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Nitrogen Fixation: N₂ → NH₃
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Nitrification: NH₃ → NO₂⁻ → NO₃⁻
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Assimilation: Plants absorb NO₃⁻
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Ammonification: Waste/dead matter → NH₃
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Denitrification: NO₃⁻ → N₂ gas
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