The Nitrogen Cycle

science · ecosystems · chemistry

Most of our air is nitrogen. About 78% of Earth's atmosphere is made of nitrogen gas, making it the most common element in the air we breathe. Even though there's so much of it floating around, plants and animals can't use it directly from the air.

Nitrogen goes round and round. Nitrogen moves through the atmosphere, soil, water, and living things in a cycle that never stops. Different processes transform nitrogen into different chemical forms so that plants can absorb it and animals can eat those plants.

Fixation makes nitrogen usable. Special bacteria in soil and ocean water can grab nitrogen from the air and turn it into a form that plants can actually use, like ammonia. This process is called nitrogen fixation, and it's the key to making atmospheric nitrogen available to life.

Plants need nitrogen to grow. Nitrogen is a crucial ingredient in proteins and DNA, which means plants need it to build strong leaves and stems. When there's not enough usable nitrogen in the soil, plants struggle to grow properly.

Decomposition releases nitrogen. When plants and animals die, bacteria break them down in a process called ammonification that releases nitrogen back into the soil. This nitrogen can then be used by new plants, keeping the cycle going.