It is the most present gas in the air. This substance is fundamental to life on Earth, as it is part of the composition of proteins, which are molecules present in all living organisms.
Nitrogen is a gas that can hardly be combined with other elements or substances. Thus, it enters and leaves our body during breathing (and also the body of other animals and plants) without changes. Thus, animals cannot obtain nitrogen directly from the air, only some bacteria are able to use nitrogen directly, transforming it into salts that are absorbed by plants. Animals get nitrogen only through food.
This transformation is made by bacteria that live in the root of plants known as legumes (beans, soybeans, peas, alfalfa, peanuts, lentils, chickpeas). This is why these plants do not make the soil poor in nitrates, as is often the case when other plant species are farmed in the same place for a long time.
With nitrogen salts, plants make other substances that make up their bodies. Animals, in turn, get these substances by ingesting plants or other living things. When animals and plants die, these nitrogen-containing substances decompose and become nitrogen salts that can be used by plants. Some of the nitrogen salts, however, are turned into nitrogen gas by some soil bacteria and return to the atmosphere. In this way nitrogen is recycled in nature.
Learn more about the nitrogen cycle
Nitrogen and fertilizers
The production of nitrogen salts can be made in chemical industries from nitrogen in the air. Nitrogen is combined with hydrogen to produce ammonia, which is then used to make nitrogen salts.
Ammonia has other applications as well: it is used in certain cleaning products and also to make many other chemical compounds.