Fertilizer, any material, natural or manufactured, which may be added to the soil to supply plant nutrients. Fertilizers are most commonly used to provide 3 of the 17 elements essential for plant growth: nitrogen (N), phosphorus (P₂0₅) and potassium (K₂0). Other less commonly required elements are sulphur, calcium, magnesium, iron, copper, manganese, boron and zinc. Manufactured or commercial fertilizers are sold on the basis of the N, P₂0₅ and K₂0 content (expressed as percentages) and usually contain a high proportion of one or more of these elements. For example, urea, a commonly used fertilizer, has the analysis 46-0-0, indicating that it contains 46% N but no P₂O₅ or K₂0. The 11-55-0 analysis of a commonly used ammonium-phosphate fertilizer indicates that it contains 11% N and 55% P₂O₅ but no K₂0.

Natural organic fertilizers (eg, barnyard manure, sewage sludge) are much lower in nutrient content and higher in bulk than are manufactured fertilizers. Manure, although variable in composition, commonly contains about 0.5% N, 0.25% P₂0₅, 0.5% K₂0 and small amounts of other essential elements. It is an important fertilizer on livestock farms and may also be used on land close to large livestock-feeding enterprises. Because of their low nutrient content and high bulk, it is impractical to transport natural organic fertilizers long distances.

The use of manufactured commercial fertilizers is unavoidable in the agricultural systems of urbanized societies. Not surprisingly, where fertilizers are available at prices that farmers can afford, crop yields are much higher than in countries where very little fertilizer is used. In Canada the highest rates of fertilizer application are in eastern Canada; the lowest in the prairies.

R.A. HEDLIN

The fertilizer industry is one of the CHEMICAL INDUSTRIES. The major fertilizer types are potassium, nitrate and phosphate fertilizers; various sulphate compounds are also important. As each depends upon different chemical processes, each has a somewhat different history in Canada.

Nitrogen fertilizers originally had to be derived from natural sources (eg, Chile's nitrate deposits). Large-scale synthetic nitrate production became possible after the 1908 discovery, by German chemists Fritz Haber and Carl Bosch, of a process for producing ammonia from atmospheric nitrogen and hydrogen. The process was applied to fertilizer production after WWI. The ammonia, known as anhydrous (ie, water-free) ammonia, may itself be used as a fertilizer or may be used to produce other fertilizers. For example, ammonium nitrate is produced by combining anhydrous ammonia and nitric acid; urea is produced by combining anhydrous ammonia and carbon dioxide from the atmosphere; ammonium phosphate is produced by combining anhydrous ammonia with phosphoric acid. In 1930, Cominco Ltd constructed an anhydrous ammonia plant at Trail, BC. Cominco Ltd became the world's first producer of granular fertilizers in 1932, of granular ammonium nitrate in 1963, and of granular urea in 1965.

Phosphate fertilizers are made from phosphate rock (about 25% phosphorus), treated with sulphuric acid to produce phosphoric acid which, in turn, is used to manufacture fertilizers such as ammonium phosphate. Canada lacks suitable phosphate rock deposits and imports the rock, mainly from the US.

Potassium fertilizer production in Canada began before the 19th century with the manufacture of POTASH from wood ashes. The industry expanded until the late 19th century, when Germany became the world's major potash supplier. Potash deposits were found in Saskatchewan in 1943 but development did not begin until 1954, when the Potash Corporation of America sank the first shaft at Patience Lake, Saskatchewan. Of the major fertilizer companies, only Cominco Ltd is engaged in developing the potash resource; however, by the mid-1980s, potash mines had been developed in Sussex, NB, and Salt Springs, NB, by the Potash Corporation of America and Dennison Mines respectively.

Sulphuric acid was first produced from metallic sulphides in 1866 and, in the 1920s, sulphuric acid production from base metal smelter gases began at Sudbury, Ontario, and Trail. The first sour-gas recovery plant in Canada was built in 1951, and there are now 45 such plants in Alberta, 3 in BC and one in Saskatchewan. Cominco Ltd, Sherritt Gordon and Esso Chemical produce sulphur dioxide gas as a byproduct of their mining and gas operations. This gas was first emitted into the atmosphere, but because of its dangerously high concentration government controls were instituted to limit emissions. In addition to being used to produce phosphate fertilizers, sulphur dioxide gas is combined with water to produce sulphuric acid, which is mixed with anhydrous ammonia to produce ammonium sulphate.