Biogeochemical Cycles
  Spheres of B. Cycles
  Nitrogen Properties
  Simple Nitrogen Cycle
  Human Influences
  Spheres of the N Cycle
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Urea (CO(NH2)2)

Urea is an organic N compound that is manufactured in large quantities. It is used as a fertilizer, including controlled-release fertilizers, and in many industrial processes. The U.S. production of urea was 9,330,000 tons in 1999 (Anon. 2000). Urea is the soluble form of N that is excreted by mammals. Therefore, large amounts of urea are added to the surface soils of feedlots and dairies. However, urea is rapidly hydrolyzed to NH3 and CO2, so it is not expected to make up a significant part of organic N in water bodies, soils, or sediments.

Suggested Reading:

Allison, F.E. 1955. The enigma of soil nitrogen balance sheets. Adv. Agron. 7:213-250.

Brady, N.C. 1974. The Nature and Properties of Soils. 8th Edition. Macmillan Publishing Co., Inc., New York.

Clark, N. 1930. Fertilizer value of manure greatly increased by immediate mixing with soil. Wisconsin Agricultural Experiment Station Bulletin 410, Madison. pp. 10-11.

David, M.B. and L.E. gentry. 2000. Anthropogenic inputs of nitrogen and phosphorus and riverine export for Illinois, USA. J. Environ. Qual. 29:494-508.

David, M.B., L.E. Gentry, D.A. Kovacic, and K.M. Smith. 1997. Nitrogen balance in and export from an agricultural watershed. J. Environ. Qual. 26:1038-1048.

Denmead, O.T., J.R. Simpson, and J.R. Freney. 1977. A direct field measurement of ammonia emission after injection of anhydrous ammonia. Soil Sci. Soc. Am. J. 41:1001-1004.

Elrashidi, M.A., V.C. Baligar, R.F. Korcak, N. Persaud, and K.D. Ritchey. 1999. Chemical composition of leachate of dairy manure mixed with fluidized bed combustion residue. J. Environ. Qual. 28:1243-1251.

Goolsby, D.A., W.A. Battaglin, G.B. Lawrence, R.S. Artz, B.T. Aulenbach, R.P. Hooper, and G.J. Stensland. 1999. Flux and Sources of Nutrients in the Mississippi-Atchafalaya River Basin. National Assessment of Gulf Hypoxia, Topic 3 Report. (http://www.nos.noaa.gov/products/pubs_hypox.html).

Lauer, D.A., D.R. Bouldin, and S.D. Klausner. 1976. Ammonia volatilization from dairy manure spread on the soil surface. J. Environ. Qual. 5:134-141.

Roe, F.G. 1951. The North American Buffalo. A Critical Study of the Species in Its Wild State. University of Toronto Press, Toronto, P.Q., Canada.

Stout, W.T., S.A. Fales, L.D. Muller, R.R. Schnabel, W.E, Purdy, and G.F. Elwinger. 1997. Nitrate leaching from cattle urine and feces in Northeast USA. Soil Sci. Soc. Am. J. 61:1787-1794.

Troeh, F.R. and L.M. Thompson. 1993. Soils and Soil Fertility. Fifth Edition. Oxford University Press, New York.

Watson, C.J., C.Jordan, S.D. Lennox, R.V. Smith, and R.W.J. Steen. 2000. Inorganic nitrogen in drainage water from grazed grassland in Northern Ireland. J. Environ. Qual. 29:225-232.

White, R.K., L.B. Owens, R.W. VanKeuren, and W.M. Edwards. 1981. Nonpoint surface runoff from cattle pasture -- hydrology and nutrients. Livestock Waste: A Renewable Resource. Proc. 4th International Symposium on Livestock Wastes--1980. Amarillo, TX. American Society of Agricultural Engineers, St. Joseph, MI, pp. 293-296.