The Facts: Nitrogen Fertilizer

Nitrogen (N) is one of the most widely distributed elements in nature, since it’s the most abundant gas in the atmosphere. While N isn’t found in mineral forms like phosphorus (P) or potassium (K), it’s largely present in organic compounds. Soil-based N undergoes many complex biological transformations that make it challenging to manage.

Many metabolic processes in plants and animals rely on nitrogen. Perhaps the best-known role of N is in forming amino acids, which make up the building blocks of protein. The human daily protein requirement ranges between 40 and 70 grams, depending on gender, age and size.

Since the Haber-Bosch process for synthesizing N fertilizer was developed early in the 20th century, its importance in maintaining the global food supply has rapidly grown. Approximately half the food produced now in the world is supported by the use of N fertilizer. Another way to look at this is that inside your body’s every cell, protein or DNA molecule, half of the N, on average, is a product of the Haber-Bosch process from a N fertilizer factory.

All N fertilizer begins with a source of hydrogen gas and atmospheric N that are reacted to form ammonia. The most-used source of hydrogen is natural gas (methane). Other sources of hydrogen, such as coal, are used in some regions. After hydrogen and N are combined under conditions of high temperature and pressure to form ammonia, many other important N-containing fertilizers can then be made. Urea is the most common N fertilizer, but many more excellent N fertilizers derive from ammonia. For example, some ammonia is oxidized to make nitrate fertilizer. This same conversion of ammonia to nitrate takes place in agricultural soils through the microbial process of nitrification.

Because the production of hydrogen gas required for the synthesis of ammonia largely comes from natural gas, the price of this primary feedstock is the major factor in the cost of ammonia production. Ammonia factories sometimes close or open in various parts of the world in response to fluctuating gas prices. Higher energy costs always translate into higher prices for all N fertilizers. There are a number of organic sources of N that are commonly used to fertilize crops. But remember that much of the N in animal manure, composts and biosolids come from crops that received applications of fertilizer N. Therefore, the N in many organic fertilizers originated as inorganic N fertilizer.

Nitrogen fertilizers clearly make an essential contribution to maintaining an adequate supply of nutritious food. However, careful management is required to keep N fertilizer in the form and in the location where it can be most useful for sustaining healthy plant growth. The tremendous benefits from N fertilizer must be balanced with the disruptive environmental impacts that may arise when N moves into areas where it’s not wanted.

Dig Deeper into Nitrogen Fertilizer Production and Technology

For more information, contact Dr. Robert Mikkelsen, Western North America Director, IPNI.

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