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This article in SSSAJ

  1. Vol. 26 No. 2, p. 186-189

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Gaseous Ammonia Losses from Urea Solutions Applied as a Foliar Spray to Various Grass Sods1

  1. D. M. H. Simpson and
  2. S. W. Melsted2



The gaseous loss of NH3 from urea applied to plant sods was studied under laboratory conditions, using various grasses which had been grown in pots under greenhouse conditions. Spray applications of N15- and C14-labeled urea solutions equivalent to 50, 100, and 150 pounds of N per acre were made to the potted plant samples which had been transferred to a bell-jar apparatus. Care was taken to spray as much of the solution as possible directly on the plant foliage. The total amount of NH3 lost through volatilization, as measured over a period of 8 to 10 days, increased with increasing rates of application. Losses ranged from about 0.5 pounds per acre with a 50-pound application to about 45 pounds with the 150-pound application. A lag period of 2 to 3 days occurred before any measurable quantity of NH3 was lost from any of the plants, with the exception of bluegrass. The greatest amount of urea hydrolysis, as measured by C14O2 evolution, occurred during this 2- to 3-day period. The amount of NH3 lost and the rate of urea hydrolysis were influenced somewhat by the type of sod to which urea was applied. In most cases, there apparently was little or no direct relationship between C14O2 evolution and the NH3 lost.

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