N-P-K, Sodium nitrate, rock phosphate limestone , calcium
|Examples of naturally-occurring inorganic fertilizers include Chilean sodium nitrate, mined "rock phosphate" and limestone (a calcium source, but mostly used to reduce soil acidity).
|Examples of manufactured or chemically-synthesized inorganic fertilizers include ammonium nitrate, potassium sulfate, and superphosphate, or triple superphosphate.
|Synthesized materials are also called - artificial fertilizers - , and may be described as - straight - , where the product predominantly contains the three primary ingredients of nitrogen (N), phosphorus (P) and potassium/potash (K), which are known as - NPK fertilizers - or - compound fertilizers -
when elements are mixed intentionally. They are named or labelled
according to the content of these three elements, thus a 5-10-5
fertilizer would have 10 percent phosphate in its ingredients. If
nitrogen is the main element, they are often described as - nitrogen fertilizers - .
|Chemist Justus von Liebig (in the 19th century) contributed greatly to understanding the role of
inorganic compounds in plant nutrition and devised the concept of Liebig's barrel to illustrate the significance of inadequate concentrations of
essential nutrients. At the same time he deemphasized the role of humus. This theory was influential in the great expansion in use of artificial fertilizers in the 20th century.
|Nitrogen fertilizer is often synthesized using the Haber-Bosch process, which produces ammonia. This ammonia is applied directly to the soil or used to produce other compounds, notably ammonium nitrate, a dry, concentrated product. It can also be used in the Odda Process to produce compound fertilizers such as 15-15-15.
|Inorganic fertilizers sometimes do not replace trace mineral elements in the soil which become gradually depleted by crops grown
there. This has been linked to studies which have shown a marked fall (up to 75%) in the quantities of such minerals present in fruit and
One exception to this is in Western Australia where deficiencies of zinc, copper, manganese, iron and molybdenum were identifed as limiting
the growth of crops and pastures in the 1940's and 1950's. Soils in Western Australia are very old, highly weathered and deficient in many
of the major nutrients and trace elements. Since this time these trace elements are routinely added to inorganic fertilizers used in
Agriculture in this state.
|In many countries there is the public perception that inorganic fertilizers "poison the soil" and result in "low quality" produce.
However, there is very little (if any) scientific evidence to support these views. When used appropriately, inorganic fertilizers enhance
plant growth, the accumulation of organic matter and the biological activity of the soil, while reducing the risk of water run-off,
overgrazing and soil erosion. The nutritional value of plants for human and animal consumption is typically improved when inorganic fertilizers
are used appropriately.