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Nitrogen is one of the most widely distributed elements in nature since it is the most abundant gas in the atmosphere. It is not found in mineral form like phosphorous or potassium are, but is largely present in organic compounds. When it is present in soil, it is subject to many complex biological transformations that make it challenging to manage.
Nitrogen is essential for many metabolic processes in plants and animals. Perhaps its best-known role is in forming amino acids, which are the building blocks for protein. The human daily protein requirement ranges between 40 to 70 grams, depending on gender, age and size.
Since the Haber-Bosch process for synthesizing Nitrogen fertilizer was developed early in the 20th century, it’s importance in maintaining the global food supply has grown rapidly. It is estimated half of the food produced in the world is supported by the use of nitrogen fertilizer. Another way to look at this is inside every cell, protein, or DNA molecule in your body, on average half of the nitrogen is a product of the Haber-Bosch process from a nitrogen fertilizer factory.
All nitrogen fertilizer begins with a source of hydrogen gas and atmospheric nitrogen that react 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 nitrogen are combined under conditions of high temperature and pressure to form ammonia, many other important nitrogen-containing fertilizers can then be made.
Urea is the most common nitrogen fertilizer, but there are many excellent nitrogen fertilizers that can be made 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 nitrogen fertilizers.
There are a number of organic sources of nitrogen commonly used to fertilize crops. But remember much of the nitrogen in animal manure, composts and biosolids come from crops that received applications of fertilizer nitrogen. Therefore, the nitrogen in many organic fertilizers originated as inorganic nitrogen fertilizer.
Nitrogen fertilizers clearly make an essential contribution to maintaining an adequate supply of nutritious food. However, careful management is required to keep nitrogen fertilizer in the form and in the location where it can be most useful for sustaining healthy plant growth. The tremendous benefits from nitrogen fertilizer must be balanced with the disruptive environmental impacts that may arise when nitrogen moves into areas where it is not wanted.
A visual tour of the nitrogen fertilizer production process can be viewed at: http://npg.ipni.net/article/NPG-3003.
Doug Shepherd is a Hardin County Extension agent for agriculture and natural resources.