Nitrogen cycle

The nitrogen cycle is the continuous process by which nitrogen moves between the atmosphere, soil, living organisms, and water in nature. Nitrogen is an essential element for all life forms because it's a key ingredient in proteins and DNA, but most organisms cannot directly use the nitrogen gas in the air, so they depend on bacteria and other processes to convert it into usable forms. Through various natural and human activities, nitrogen gets recycled through different forms—from atmospheric nitrogen to nitrates in soil to proteins in plants and animals, and eventually back to the atmosphere—creating a vital cycle that sustains ecosystems and agriculture.