Fertilizers (2)
process in which concentrated sulfuric acid, water, and ground phosphate rock produce a compound with a much higher P2O5 content. Potassium is important because of its essential role in water absorption. Also, potassium promotes early growth, improves stem strength, and improves most aspects of the fruit the plant bears. Organic potassium fertilizers include plant residues (wood ashes, hay, and leaves), manures and compost, and natural mineral sources (granite dust, greensand, and basalt rock). Mineral fertilizers tend to have insoluble potassium content, which makes absorption really slow, whereas potassium sources of KCl and KNO3 are soluble, which allows the potassium to be taken in quickly. Secondary Elements Sulfur, calcium, and magnesium constitute the secondary elements. Sulfur is a component of the amino acids methionine and cysteine in plant tissue. It is also shown that sulfur deficiency can result in chlorosis and retardation of plant growth. Elemental sulfur can be found in salt deposits along the Gulf Coast of the United States. Calcium is used for the continuous cell division in a plant, and is also involved in the absorption of nitrogen. Calcium is included in fertilizers through the compounds calcium nitrate, calcium ammonium nitrate, and calcium cyanamide. Magnesium is essential to the structure of chlorophyll, and thus the entire photosynthetic process as a whole. Magnesium is commonly found in the earth’s crust in the form of carbonates and silicates. Chemically, dolomite, CaMg(CO3) 2, and langbeinite, K2SO4•2MgSO4, are used as magnesium supplements. Trace Elements Most trace elements are found naturally in the soil in appropriate amounts. Thus, only in rare circumstances do these elements need to be added to supplement fertilizers. These elements include boron, cobalt, copper, iron, manganese, molybdenum, and zinc.	Sources: Considine, Douglas, ed. Van Nostrand’s Scientific Encyclopedia. New York: Van Nostrand Reinhold, 1995. Hiscox, Gardner, ed. Henley’s Twentieth Century Book of Ten Thousand Formulas, Processes, and Trade Secrets. Cornwells Heights, PA: Publisher’s Agency, 1981. McGraw Hill Encyclopedia of Science and Technology. New York: McGraw-Hill, 1997. Mount, Ellis, and Barbara List, eds. Milestones in Science and Technology: The Ready Reference Guide to Discoveries, Inventions, and Facts. Phoenix, AZ: Oryx, 1987. Organic Gardening Magazine. The Encyclopedia of Organic Gardening. Emmaus, PA: Rodale, 1978. Singer, Charles, ed. A History of Technology: The Late Nineteenth Century. New York: Oxford, 1958. The New Illustrated Science and Invention Encyclopedia. Westport, CT: H.S. Stuttman, 1989. http://www.cargillfertilizer.com/About/phosfacsf.htm
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