As a liquid, it is also colorless and odorless, resembling ordinary water in appearance, density and viscosity. Nitrogen is of economic importance. Nitrogen is the choice gas for this process because of its unreactivity with the oil. In industrial soldering and welding operations where it is important to keep other atmospheric gases away from the high-temperature part of the work. Production of fertilizers as nitrogen compounds are essential for plant growth.
Liquid ammonia is injected directly into the soil for certain crops such as corn and sugar beets.
Ammonium sulfate is manufactured because of its widespread use as a fertilizer. Its only drawback as a fertilizer is that it tends to leave an acidic residue in the soil. Ammonium nitrate, because of its high nitrogen content, it is also used as a fertilizer. Urea is another nitrogen-containing compound that is used as a fertilizer. It is also a protein supplement in cattle feed.