418 • Feldspars Global Resources Million Metric Tons Source: Mineral Commodity Summaries, 2009Data from the U.S. Geological Survey, . U.S. Government Printing Office, 2009. Argentina Brazil China Colombia Czech Republic Egypt France Germany India Iran Italy Japan Malaysia Mexico Poland Portugal South Korea Spain Thailand Turkey United States Venezuela Other countries 290,000 130,000 2,000,000 100,000 490,000 350,000 170,000 160,000 260,000 4,200,000 250,000 350,000 130,000 400,000 600,000 3,800,000 200,000 650,000 700,000 440,000 800,000 600,000 1,200,000 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 Feldspar: World Mine Production, 2008 icut, togrindfeldspar forthe newly developedpottery industry in the United States. The largest production of feldspar in the United States is in North Carolina, followed by Virginia, Cali- fornia, Oklahoma, Georgia, Idaho, and South Dakota. Crude feldspar is also produced by at least thirty-eight other countries. China, Turkey, Italy, and Thailand jointly produce approximately 60 percent of the world’s total feldspar. U.S. production of crude feld- spar is about 3 percent of the world total. Obtaining Feldspar The method used to obtain feldspar depends on the type of deposit to be mined. Most feldspar can be quarried by open-pit mining. Some feldspars are mined by boring down through distinct zones within pegmatite dikes, but many deposits require the use of explosives and drills. Dragline excavators are used to mine feldspathic sands. High-grade feldspar can be dry-processed. It is sent through jaw crushers, rolls, and oiledpebble mills,and is finally subjected tohigh- intensity magnetic or electrostatic treatments that re- duce the iron content to acceptable levels. Feldspathic sands are crushed and rolled, then processed by a three-step froth flotation sequence that removes mica, extracts the iron-bearing miner - als, and finally separates the quartz residuals. Some- times the last flotation procedure is omitted so that a feldspar-quartz mixture can be sold to the glass- making industry. The feldspar is ground to about twenty mesh for glassmaking and to two hundred mesh or finer for ceramic and filler applications. Uses of Feldspar Feldspar is used in the manufacturing of soaps, glass, enamels, and pottery. As a scouring soap, its interme- diate hardness, angular fracture, and two directions of cleavage cause it to form sharp-edged, gritty parti- cles that are hard enough to abrade but soft enough not to cause damage to surfaces. In glassmaking, feld- spar brings alumina, together with alkalies, into the melt. This enhances the workability of the glass for shaping and gives it better chemical stability. Feldspar is used primarily as a flux in ceramics mix- tures to make vitreous china and porcelain enamels. The feldspar is ground to a very fine state and mixed with kaolin or clay and quartz. The feldspar fuses at a temperature below most of the other components and acts as a vitreous binder, cementing the material together. Fused feldspar is also used as the major part of the glaze on porcelain ware. Dion C. Stewart Further Reading Chatterjee, Kaulir Kisor. “Feldspar.” In Uses of Indus- trial Minerals, Rocks, and Freshwater. New York: Nova Science, 2009. Deer, W. A., R. A. Howie, and J. Zussman. Framework Silcates: Feldspars. Vol 4A in Rock-Forming Minerals. 2d ed. London: Geological Society, 2001. Klein, Cornelis, and Barbara Dutrow. The Twenty-third Edition of the Manual of Mineral Science. 23d ed. Hoboken, N.J.: J. Wiley, 2008. Kogel, Jessica Elzea, et al., eds. “Feldspars.” In Indus- trial Minerals and Rocks: Commodities, Markets, and Uses. 7th ed. Littleton, Colo.: Society for Mining, Metallurgy, and Exploration, 2006. Ribbe, R. H., ed. Feldspar Mineralogy. 2d ed. Washing- ton, D.C.:Mineralogical Societyof America,1983. Smith, Joseph V., and William L. Brown. Feldspar Min- erals. 2d rev. and extended ed. New York: Springer, 1988. Wenk, Hans-Rudolf, and Andrei Bulakh. Minerals: Their Constitution and Origin. New York: Cambridge University Press, 2004. Global Resources Feldspars • 419 Source: Mineral Commodity Summaries, 2009 Data from the U.S. Geological Survey, .U.S.GovernmentPrinting Office, 2009. Glass 65% Pottery and other 35% U.S. End Uses of Feldspar Web Sites U.S. Geological Survey Feldspar http://minerals.er.usgs.gov/minerals/pubs/ commodity/gemstones/sp14-95/feldspar.html U.S. Geological Survey Feldspar: Statistics and Information http://minerals.usgs.gov/minerals/pubs/ commodity/feldspar See also: Abrasives; Ceramics; China; France; Igne- ous processes, rocks, and mineral deposits; Italy; Mex- ico; Pegmatites; Plutonic rocks and mineral deposits; Spain; Thailand; Turkey; United States. Fermi, Enrico Category: People Born: September 29, 1901; Rome, Italy Died: November 28, 1954; Chicago, Illinois Fermi was an Italian physicist knownfor his workon the first nuclear reactor and his theory of beta decay. He contributedto quantum theory, statistical mechan- ics, and nuclear and particle physics. He conducted investigations on the atom’s nucleus and experi- mented with uranium, which led to his observation of nuclear fission. His discovery of a methodology to release nuclear energy earned him the Nobel Prize in Physics in 1938. Biographical Background Enrico Fermi was born in Rome, Italy, the son of a railroad official and a schoolteacher. He excelled in school, sharing his interests with his older brother, Giulio, who died in 1915 after minor throat surgery. After high school, Fermi studied at the University of Pisa from 1918 to 1922, com- pleting his undergraduate degree and Ph.D. in physics. Fermi solved the Fourier analysis for his college entrance exam and published his first sci- entific work on electrical charges in transient conditions in 1921. Fermi received a fellowship to work at the Uni- versity of Göttingen in Germany in 1924. He taught math at the University of Rome and the University of Florence, where he researched what would later be called the Fermi-Dirac statistics. Fermi studied at Leyden in the Netherlands and married Laura Capon in 1928. Their daughter, Nella Fermi Weiner (1931-1995), and son, Giulio (1936-1997), both obtainedPh.D.’s.Fermi wasone of the only phys- icists of the twentieth century toexcel in both theoret- ical and applied nuclear physics. He died from stom- ach cancer, resulting from radiation exposure, on November 28, 1954. After his death, his lecture notes were transcribed into books, andschools and many awards were named in his honor. Three nuclear reactor installations were named after him, as was “fermium,” the one hun- dredth element on the periodic table. Impact on Resource Use Fermi’s research at the University of Rome led to the discovery of uranium fission in 1934. In 1939, on the Columbia University campus, the first splitting of the uranium atom took place. Fermi’s focus was on 420 • Fermi, Enrico Global Resources Enrico Fermi’s work with radioactiveisotopes led to the development of the atomic bomb. (NARA) the isotope separation phase of the atomic energy project. In 1942, he led a famous team of scientists in lighting the first atomic fire on earth at the Univer- sity of Chicago. His studies led to the construction of the first nuclear pile, called Chicago Pile-1, whereby he assessedthe properties offission, thekey toextract- ing energy from nuclear reactions. Another example of his impact was noted on July 16, 1945, when Fermi supervised the design and as- sembly of the atomic bomb. Fermi dropped small pieces of paper as the wave of the blast reached him and then measured the distance those pieces were blown. This allowed him to estimate the bomb’s en- ergy yield. The calculations became known as the “Fermi method.” His discovery of how to release nu- clear energy encouraged the development of many peaceful uses for nuclear energy. Fermi discovered induced radioactivity (radioac- tive elements produced by the irradiation of neu- trons) and nonexplosive uranium, which is trans- muted into plutonium (a vital element in the atomic and hydrogen bombs and the first atomic subma- rine). His research led to the creation of more than forty artificial radioactive isotopes, and his theory of neutron decay became the model for future theories of particle interaction. Gina M. Robertiello See also: Hydrogen; Nobel, Alfred; Nuclear energy; Nuclear Energy Institute; Uranium. Ferroalloys Category: Mineral and other nonliving resources Where Found Ferroalloy production occurs in many countries around the world, but the primary ferroalloy-produc- ing countries are China, South Africa, Ukraine, Russia, and Kazakhstan. These five countries produce more than 74 percent of the world’s ferroalloy supply. How- ever, because the various ferroalloys contain a num- ber ofdifferentelements, manyparts ofthe worldsup- ply minerals important in ferroalloy production. Primary Uses Ferroalloys are used extensively in the iron and steel industry. The type of alloy produced depends upon the properties of the element that is added to the iron. Stainless steel, high-strength steels, tool steels, and cast irons are the major ferroalloy products. Some ferroalloys are also used to produce metal coatings, catalysts, electrodes, lighting filaments, aerospace and marine products, medical implants, and household batteries. Technical Definition Ferroalloys constitute a wide variety of alloyed metals that combine alarge percentage of iron with a smaller percentage of one or more elements. Combining other elements with iron imparts superior strength to thesealloys, and thisincreased strengthenables the metals to be used in many important products within the metallurgical industry. Ferroalloys have lower melting points than do the pure elements that form them; therefore, they are incorporated more easily into molten metal. Manganese, chromium, magne- sium, molybdenum, nickel, titanium, vanadium, sili- con, cobalt, copper, boron, phosphorus, niobium, tungsten, aluminum, and zirconium are the primary elements mixed in varying proportions with iron to produce ferroalloys. Ferroalloys are produced pri- marily in electric arc furnaces; the nonferrous metal combines with the iron at high temperatures to pro- duce the various types of steel. Description, Distribution, and Forms Much of the stainless-steel production of Europe, Asia, and North and South America is possible because of ferrochromium.In 2007,approximately 29metric tons of stainless steel were produced throughout the world. Most chromite ore miningtakes placein China, India, South Africa, Russia, Turkey, and Kazakhstan. The ma- jority of chromiteore is smelted in electric arc furnaces to produce ferrochromium,which is thenexported to the countries that manufacture stainless steel. Ferromanganeseand silicomanganese are primary ingredients in steelmaking. Most of the U.S. supply of these alloys is imported from South Africa, although China, Brazil, India, and Ukraine are also important producers. The United States also produces some ferromanganese at a plant near Marietta, Ohio. Be- sides being a key component in steel manufacturing, manganese is used in the production of household batteries. Silicomanganese production at plants in New Haven, West Virginia, the United Kingdom, and Ukraine has been vital to steelmaking for a number of years. Global Resources Ferroalloys • 421 Ferrosilicon is a deoxidizing agent in cast iron and steel production. China, Brazil, and Russia are the main producers offerrosilicon, withChina producing more than four times as much as the other two coun- tries. More than 99 percent of ferronickel use within the United States is for stainless steel and heat-resistant steel. Stainless-steel cooking pots, pans, and kitchen sinks are products of the ferronickel industry. The United States does not produce any primary nickel but instead produces a remelt alloy with small per- centages ofchromium and nickelfrom recycledmate- rials. Japan, New Caledonia, Colombia, Greece, Ukraine, Indonesia, the Dominican Republic, and Venezuela lead the world in ferronickel production. Another major ferroalloy is ferromolybdenum, a component of stainless steels, tool steels, and cast iron. About 80 percent of world production of ferro- molybdenum takes place in Chile, China, and the United States, while the remainder occurs in Canada, Mexico, and Peru. Ferrotitanium plays a large role in the steel indus- try as a deoxidizing and stabilizing agent as well as an alloy that assists in controlling the grain size of steel. Titanium is not naturally found in metallic form but instead is mined from titanates, oxides, and silico- titanites. Ferrotitanium is then produced by an in- duction melting process. Steels with a high titanium content include stainless, high-strength, and intersti- tial-free (space-free) forms. Other important ferroti- tanium uses include catalysts, pigments, floor cover- ings, roofing material, aerospace products, medical implants, armor, and marine industrial goods. Major producers of ferrotitanium include China, India, Ja- pan, Russia, the United Kingdom, and the United States. Ferrovanadium, used in the manufacture of cata- lysts and chemicals, is produced in the United States mostly from petroleum ash and residues as well as from tar sands. China and South Africa contribute 71 percent of the world’s supply of ferrovanadium, while Russia makes up most of the remaining supply. History Steel has been produced by a number of methods since before the fifteenth century, but only since the seventeenth century has it been produced effi- ciently. The Bessemer process, invented in the mid- 1800’s by Sir Henry Bessemer, enabled steel to be mass-produced in a cost-effective manner. Improve - ments on theBessemer process included the Thomas- Gilchrist process and the Siemens-Martin process of open-hearth steel manufacture. Basic oxygen steel- making, also known as the Linz-Donawitz process, was developed in the 1950’s, and although the Bessemer process and other processes continued to be used for a few more years, basic oxygen steelmaking soon became the process of choice for modern steel manu- facture. Creating Ferroalloys Ferroalloys have been used in the steel manufactur- ing industry primarily since the 1960’s. In the twenti- eth century, metallurgists discovered that adding vary- ing amounts of manganese, silicon, or aluminum to the molten steel pulled oxygen away from the melted material, thus allowing for sound castings without bubbles or blowholes. The other ferroalloys—those containing chromium, tungsten, molybdenum, vana- dium, titanium, and boron—provide a method for making specialty steels other than ordinary carbon steel. By adding small amounts of the other metals, high-strength, heat-resistant steels, such as stainless steel, can be produced. The amount of steel that a country produces is often considered to be an important indicator of eco- nomic progress. Therefore, the production of ferro- alloys within the iron and steel manufacturing indus- try is also a key factor of the economy of the countries in which it takes place. In the twenty-first century, the economic booms in China and India brought about a large increase in demand for steel products and a cor- responding needfor a large number of workers inthis industry. The top producers of steel in the world are, in order of metric-ton production per year, China, Ja- pan, Russia, and the United States. Each of these countries has many thousands of workers in its steel industry and in the mining industries, which supply the raw materials for iron and steel production. Uses of Ferroalloys The primary use of ferroalloys is in the manufactur- ing of iron and steel. Combining various metallic ele- ments with ironresults in a strong, stableproduct vital to many industries. Stainless and heat-resisting steels are produced from ferrochromium, ferrotitanium, and ferronickel. Ordinary carbon steel rusts, but stainless steel resists corrosion because of the chro - mium oxide film it contains. In general, at least 11 percent chromium must be added to the steel in or - 422 • Ferroalloys Global Resources der to produce the stainless quality. Up to 26 percent chromium must be added if the stainless steel is to be exposed to harsh environmental conditions. Al- though stainless steel has a huge number of applica- tions in modern society, it is mostly used for cutlery, appliances, surgical instruments, cooking equip- ment, and aerospace parts. Because stainless steel is also resistant to bacterial growth, it is important in the cooking and medical industries. Stainless steel is also used in jewelry and firearm production. Ferrochromium is used in the chemical industry as a surface treatment coating for metals. Besides the primary uses of ferroalloys in steelmaking, these sub- stances are also used to produce catalysts in catalytic converters, pigments in paint, grinding and cutting tools, lighting filaments, and electrodes. Ferrosilicon is used by the military to produce hydrogen for bal- loons in a process that combines sodium hydroxide, ferrosilicon, and water. Lenela Glass-Godwin Further Reading Corathers, Lisa A. “Manganese.” USGS Minerals Year- book (2007). Dunkley, J. J., and D. Norval. “Atomisation of Ferro- alloys.” In Industrial Minerals and Rocks, edited by Jessica Elzea Kogel. 6thed. Littleton, Colo.: Society of Mining, Metallurgy, and Exploration, 2004. Jones, Andrew. “The Market and Cost Environments for Bulk Ferroalloys.” In International Conference on Innovations in theFerroalloy Industry. New Delhi:The Indian Ferro Alloy Producers’ Association, 2004. Papp, J.F. “Chromite.” InIndustrial Minerals and Rocks, edited by Jessica Elzea Kogel. 6th ed. Littleton, Colo.: Society of Mining, Metallurgy, and Explora- tion, 2004. Web Site U.S. Geological Survey Minerals Information: Ferroalloys Statistics and Information http://minerals.usgs.gov/minerals/pubs/ commodity/ferroalloys/ See also: Aluminum; Bessemer process; Boron; Chromium; Cobalt; Copper; Magnesium; Manganese; Molybdenum; Nickel; Niobium; Siemens, William; Silicon; Steel; Steel industry; Titanium; Tungsten; Va - nadium; Zirconium. Fertilizers Categories: Plant and animal resources; products from resources Fertilizers, those materials that are used to modify the chemical composition of the soil in order to enhance plant growth, represent an important use of natural resources because agricultural systems are dependent upon the ability to retain soil fertility. Among the essen- tial nutrients provided in fertilizers are calcium, mag- nesium, sulfur, nitrogen, potassium, and phosphorus. Background It has been said that civilization owes its existence to the 15-centimeter layer of soil covering the Earth’s landmasses. This layer of topsoil represents the root zone for the majority of the world’s food and fiber crops. Soil is a dynamic, chemically reactive medium, and agricultural soils must provide structural support for plants, contain a sufficient supply of plant nutri- ents, and exhibit an adequate capacity to hold and ex- change minerals. As plants grow and develop, they re- move the essential mineral nutrients from the soil. Since normal crop production usually requires the re- moval of plants or plant parts, nutrients are continu- ously being removed from the soil. Therefore, the long-term agricultural utilization of any soil requires periodic fertilization to replace these lost nutrients. Fertilizers are associated with every aspect of this nu- trient replacement process. The application of fertil- izer is based on a knowledge of plant growth and de- velopment, soilchemistry, and plant-soil interactions. Soil Nutrients Plants require an adequate supply of both macro- nutrients (calcium, magnesium, sulfur, nitrogen, po- tassium, and phosphorus) and micronutrients (iron, copper, zinc, boron, manganese, chloride, and mo- lybdenum) from the soil. If any one of these nutrients is notpresent insufficient amounts, plant growthand, ultimately, yieldswill be reduced. Becausemicronutri- ents are required in small quantities and deficiencies in these minerals occur infrequently, the majority of agricultural fertilizers contain only macronutrients. Although magnesium and calcium are utilized in large quantities, most agricultural soils contain an abundance ofthese twoelements, eitherderived from parent material or added as lime. Most soils also con - Global Resources Fertilizers • 423 tain sufficient amounts of sulfur from the weathering of sulfur-containing minerals, the presence of sulfur in other fertilizers, and atmospheric pollutants. The remaining three macronutrients (nitrogen, potassium, and phosphorus) are readily depleted and are referred toas fertilizer elements. Hence, theseele- ments must be added to most soils on a regular basis. Fertilizers containingtwo ormore nutrientsare called mixed fertilizers. A fertilizer labeled 10-10-10, for example, means that the product contains 10 percent nitrogen, 10 percent phosphorus, and 10 percent po- tassium. Since these elements can be supplied in a number of different forms, some of which may not be immediately useful to plants, most states require that the label reflect the percentage of nutrients available for plantutilization. Fertilizers are produced ina wide variety of single and mixed formulations, and the per- centage of available nutrients generally ranges from a low of 5percent to ahigh of 33 percent. Mixedfertiliz- ers may also contain varying amounts of different micronutrients. Fertilizer Production Nitrogen fertilizers can be classified as either chemi- cal or natural organic. Naturalorganic sources are de- rived from plant and animal residues and include such materials as animal manures, cottonseed meal, and soybean meal. Since natural organic fertilizers contain relatively small amounts of nitrogen, com- mercial operations rely on chemical fertilizers de- rived fromsources otherthan plantsand animals.The major chemical sources of nitrogen include both am- monium compounds and nitrates. The chemical fixa- tion of atmospheric nitrogen by the Claude-Haber ammonification process is the cornerstone of the modern nitrogen fertilizer manufacturing process. Once the ammonia is produced, it can be applied di- rectly to the soil as anhydrous ammonia, or it can be mixed with water and supplied as a solution of aque- ous ammonia and used in chemical reactions to pro- duce other ammonium fertilizers or urea, or con- verted to nitrates that can be used to make nitrate fertilizers. Some organic fertilizers contain small amounts of phosphorus, and organically derived phosphates from guano or acid-treated bonemeal were used in the past. However, the supply of these materials is scarce. Almost all commercially produced agricultural phos - phates are applied as either phosphoric acid or super - phosphate derived from rock phosphate. The major phosphate component in commercially important deposits of rock phosphate is apatite. The apatite is mined, processed to separate the phosphorus- containing fraction from inert materials, and then treated with sulfuric acid to break the apatite bond. The superphosphate precipitates out of the solution and sets up as a hard block, which can be mechani- cally granulated to produce a fertilizer containing cal- cium, sulfur, and phosphorus. Potassium fertilizers, commonly called “potash,” are also obtained from mineral depositsbelow theEarth’s surface. Themajor commercially availablepotassium fertilizers are potas- sium chloride extracted from sylvanite ore, potassium sulfate produced by various methods (including ex- traction from langbeinite or burkeite ores or chemi- cal reactionswith potassium chloride),and potassium nitrate, which can be manufactured by several differ- ent chemical processes. Although limited, there are sources of organic potassium fertilizers such as to- bacco stalks and dried kelp. While the individual nitrogen, phosphorus, and potassium fertilizers can be applied directly to the soil, they are also commonly used to manufacture mixed fertilizers. From two to ten different materials with widely different properties are mixed togetherin the manufacturing process. The three most common processes utilized in mixed fertilizer production are the ammonification of phosphorus materials and the subsequent addition of other materials, bulk blend- ing of solid ingredients, and liquid mixing. Fillers and make-weight materials are often added to make up the difference between the weight of fertilizer materi- als required to furnish the stated amount of nutrient and the desired bulk of mixed products. Mixed fertil- izers have the obvious advantage of supplying all the required nutrients in one application. Benefits and Costs For every crop there is a point at which the yield may continue to increase with application of additional nutrients, but the increase will not offset the addi- tional cost of the fertilizer. Therefore, considerable care should be exercised when applying fertilizer.The economically feasible practice, therefore, is to apply the appropriate amount of fertilizer to produce maxi- mum profit rather than maximum yield. Moreover, since excessive fertilization can result in adverse soil reactions that damage plant roots or produce unde - sired growth patterns, overfertilization can actually decrease yields. If supplied in excessive amounts, some 424 • Fertilizers Global Resources of the micronutrients are toxic to plants and will dra - matically reduce plant growth. Fertilizer manufactur- ers must ensure that their products contain the speci- fied amounts of nutrients indicated on their labels and that there are no contaminants that could ad- versely affect plant yield directly or indirectly through undesirable soil reactions. The environment can also be adversely affect by overfertilization. Excess nutrients can be leached through the soil into underground water supplies and/or removed from the soil in the runoff water that eventually empties into streams and lakes. High levels of plant nutrients in streams and lakes (eutrophica- tion) can result in abnormal algal growth, which can cause serious pollutionproblems. Water thatcontains excessive amounts of plant nutrients can also pose health problems if it is consumed by humans or live- stock. Importance to Food Production Without a doubt, the modern use of fertilizer has dramatically increased crop yields. If food and fiber production is to keep pace with the world’s growing population, increasedreliance on fertilizers willbe re- quired inthe future. With ever-increasing attention to the environment, future research will primarily be aimed atfinding fertilizermaterials thatwill remainin the field to which they are applied and at improving application and cultivation techniques to contain ma- terials withinthe designatedapplication area.The use of technology developed from discoveries in the field of molecular biology to develop more efficient plants holds considerable promise for the future. D. R. Gossett Further Reading Altieri, MiguelA. Agroecology:The ScientificBasis ofAlter- native Agriculture. Boulder, Colo.: Westview Press, 1987. Black, C. A. Soil-Plant Relationships. 2d ed. Malabar, Fla.: R. E. Krieger, 1984. Brady, Nyle C., and Ray R. Weil. The Nature and Prop- erties of Soils. 14th ed. Upper Saddle River, N.J.: Prentice Hall, 2008. Elsworth, Langdon R., and Walter O. Paley, eds. Fertil- izers: Properties, Applications, and Effects. New York: Nova Science, 2008. Engelstad, Orvis P. Fertilizer Technology and Use.3ded. Madison, Wis.: Soil Science Society of America, 1986. Follett, RoyH., Larry S.Murphy, andRoy L.Donahue. Fertilizers and Soil Amendments. Englewood Cliffs, N.J.: Prentice-Hall, 1981. Hall, William L., Jr., and Wayne P. Robarge, eds. Envi- ronmental Impact of Fertilizer on Soil and Water. Wash- ington, D.C.: American Chemical Society, 2004. Havlin, John L., Samuel Tisdale, Werner Nelson, and James D. Beaton. Soil Fertility and Fertilizers: An Intro- duction to Nutrient Management. 7th ed. Upper Sad- dle River, N.J.: Pearson Prentice Hall, 2005. Web Sites Agriculture and Agri-Food Canada Manure, Fertilizer, and Pesticide Management in Canada http://www4.agr.gc.ca/AAFC-AAC/display- afficher.do?id=1178825328101&lang=eng Economic Research Service, U.S. Department of Agriculture U.S. Fertilizer Use and Price http://www.ers.usda.gov/Data/FertilizerUse See also: Agriculture industry; Eutrophication; Green Revolution; Guano; Horticulture; Hydropon- ics; Monoculture agriculture; Nitrogen and ammo- nia; Potash; Slash-and-burn agriculture; Soil degrada- tion. Fiberglass Category: Products from resources Fiberglass has many practical uses, especially in struc- tural applications and insulation, because its fibers are stronger than steel and will not burn, stretch, rot, or fade. Definition Fiberglass consists offine, flexible glassfilaments or fi- bers drawn or blown directly from a glass melt. These fibers may be many times finer than human hair. Overview Fiberglass is typically made in a two-stage process. Glass is first melted and formed into marbles in an electric furnace, and then fibers are drawn continu - ously through holes in aplatinum bushingand wound Global Resources Fiberglass • 425 onto a revolving drum like threads on spools. The drum can pull out more than 3 kilometers of fibers in a minute, and up to 153 kilometers of fiber can be drawn from one glassmarble that is 1.6 centimeters in diameter. For a given set of operating conditions, the size of the fibers is uniform, with diameters varying from approximately 0.00025 centimeter to 0.00125 centimeter, depending on the application. Some ultrafine fibers have diameters of 0.0000762 centime- ter or less. A typical compositionof fiberglass (E glass) is 54 percent silica, 15 percent alumina, 16 percent calcia, 9.5 percent boron oxide, 5 percent magnesia, and 0.5 percent sodium oxide by weight. Because of its low alkali (sodium) content, this type of fiberglass has good durability and strength, and because of the boron, it can be melted at reasonably low tempera- tures. Coarse glass fibers were used by the ancient Egyp- tians to decorate dishes, cups, bottles, and vases. At the Columbian Exposition in Chicago in 1893, Ed- ward Drummond Libbey exhibited a dress made of fiberglass and silk. During World War I (1914-1918), the Germans produced fiberglass in small diameters as a substitute for asbestos. In 1938, the Owens- Corning Fiberglass Corporation was formed in the United States, and fiberglass production was soon started on a commercial scale. Fiberglass wool, made of loosely intertwined strands of glass with air pockets in between, is an excellent in- sulator against heat and cold. Itis used asa thermal in- sulator in the exterior walls and ceilings of homes and other buildings, as a thermal and electrical insulator in furnaces, ovens, water heaters, refrigerators, and freezers, and as a thermal and sound insulator in air- planes. Fiberglass is commonly combined with plastic polymers to produce laminates that can be formed into complex shapes for use in automobile and truck bodies, boats, carport roofs, swimming pool covers, and other items requiring light weight, strength, and corrosion resistance. In addition, fiberglass is woven into avariety offabrics, tapes,braids, andcords foruse in shower curtains, fireproof draperies, and electrical insulation of wire and cable in electric motors, gener- ators, transformers, meters, and electronic equip- ment. Alvin K. Benson See also: Aluminum; Boron; Glass; Petrochemical products; Sedimentary processes, rocks, and mineral deposits; Silicates; Silicon; Textiles and fabrics. Fires Category: Environment, conservation, and resource management Wildfire is an integral part of wilderness life cycles, helping keep ecosystems healthy and diverse in plant and animal life. Controlled human-set fires aid farm- ers, ranchers, and foresters in making their lands more productive. Background Fire is both inevitable and necessary to most land eco- systems. Every day, lightning strikes the ground about eight million times globally, and one stroke in twenty- five can start a fire. Even so, lightning accounts for only about 10 percent of ignitions; humans are the leading agent in setting fires. Fire was one of the first tools humans used to shape their environment, and it has remained among the most common tools ever since. Add tolightning and humans as agents the mol- ten rock from volcanoes and the sparks sometimes caused by rock slides, and not surprisingly millions of hectares of land burn worldwide every year. Because fire is so prevalent, ecosystemshave evolved tolerance to it or even a symbiotic dependence on it. Wildfires foster decomposition of dead material, recy- cle nutrients, control diseases by burning infected plants and trees, help determine which plant species flourish in a particular area, and in some cases even play arole ingerminating seeds. Purposefully setfires, today called controlled burns, have flushed game for hunters since prehistoric times and are still put to work fertilizing fields and clearing them of unwanted plants, pruning forests, combating human and ani- mal enemies, and eliminating dead, dry materials be- fore they can support a destructive major fire. Types of Fire Not all fires are equal. Scientists distinguish five basic types in increasing order of intensity and destructive potential: those that smolder in deeplayers of organic material; surface backfires, which burn against the wind; surface headfires, which burn with the wind; crown fires, which advance as a single front; and high- intensity spotting fires, during which winds loft burn- ing fragments that ignite separate fires. Moreover,the intensity, likelihood, and range of fires for any locale depend upon the climate, season, terrain, weather (es - 426 • Fires Global Resources pecially the wind), relative moisture, and time since a previous burn. The dominant species of plant also af- fects which type of fire an ecosystem can support. Tundra and Far-Northern Forests Fires visit northern ecosystems infrequently because they retain a great deal of moisture even during the summer: There are intervals of sixty to more than one hundred years between fires for forests and several centuries for tundra. Caused primarily by lightning, light surface fires are most common. Crown fires are rare. The seeds of many northern tree species, such as pine andspruce, germinate well onlyon soil that a fire has bared. Fire does not occur in high Arctic tundra and plays only a minor role in the development of low Arctic tundra. Grasslands Grasslands of all kinds rebound from surface fires in about three years. In shortgrass and mixed-grass prairies, grass species, especially buffalo grass and blue grama, survive fires well, while small cacti and broadleaf plants succumb easily, assuring dominance of the grasses. For this reason, cattle ranchers fre- quently burn the prairies to remove litter and inedi- ble species,thus improving thedistribution of grazing fodder. In tallgrass prairies, big bluestem, Indian grass, and switchgrass increase after a fire, whereas cold- season grasses, such as Kentucky bluegrass, are devas- tated, and fires prevent invasions of trees and woody shrubs. Semidesert and Desert Regions Similarly, surface fires control shrubs in semidesert grass-shrub lands on mesas and foothills, while allow- ing the fire-resistant mesquite to flourish. Desert sage- brush areas in the intermountain West have a surface fire about every thirty-two to seventy years. A burned area takes about thirty years to recover fully, although horsebrush and rabbitbrush come back quickly. Global Resources Fires • 427 Wildfires, like this one in 1996 in Calabasas, California, are integral aspects of the natural cycles of life, but too often and increasingly they encroach on places in which humans dwell. (AP/Wide World Photos) . as lime. Most soils also con - Global Resources Fertilizers • 423 tain sufficient amounts of sulfur from the weathering of sulfur-containing minerals, the presence of sulfur in other fertilizers,. rabbitbrush come back quickly. Global Resources Fires • 427 Wildfires, like this one in 1996 in Calabasas, California, are integral aspects of the natural cycles of life, but too often and increasingly. His research led to the creation of more than forty artificial radioactive isotopes, and his theory of neutron decay became the model for future theories of particle interaction. Gina M. Robertiello See