The process of converting atmospheric nitrogen into a usable form for plants is called nitrogen fixation. This biochemical process primarily occurs through nitrogen-fixing bacteria in the soil or in symbiotic relationships with legume roots. These bacteria convert atmospheric nitrogen (N₂) into ammonia (NH₃), which plants can utilize for growth. Nitrogen fixation is essential for maintaining the nitrogen cycle and supporting agricultural productivity, as nitrogen is a critical component of amino acids and nucleic acids.