Where does nitrogen make up most of the atmosphere?

Nitrogen is the dominant gas in Earth’s atmosphere, making up roughly 78 percent of dry air. It is present globally because Earth’s atmosphere is well mixed over time. Although nitrogen is abundant, most organisms cannot use atmospheric nitrogen directly; it must first be fixed into usable compounds by microbes, lightning, or industrial processes. This makes the nitrogen cycle essential for life and agriculture. Nitrogen is also widely used in industry as an inert gas and in liquid form for cooling and freezing.