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This article in SSSAJ

  1. Vol. 49 No. 2, p. 376-381
    Received: Oct 24, 1983
    Accepted: Oct 8, 1984

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Effect of Environmental Factors on Ammonia Volatilization from a Urea-Fertilized Soil1

  1. R. J. B. Bouwmeester2,
  2. P. L. G. Vlek3 and
  3. J. M. Stumpe3



A greenhouse experiment using 15N followed by wind tunnel experiments using a micrometeorological technique were conducted to identify some of the factors that contribute most significantly to ammonia (NH3) volatilization in a simulated semiarid environment following application of urea. An Aridic Calciustolls with high urease activity was subjected to a variety of initial soil moisture contents, rainfall patterns, wind speeds, air-humidity, and urea application methods. Losses of broadcast urea-N in the greenhouse at 42-d harvest, presumably due to NH3 volatilization, were reduced from 40% with a first rain of 1 cm (7 d after fertilizer application) to 13% with a first rain of 4 cm. Nitrogen losses were increased by 8% when initial soil moisture was increased from 21% (≅ permanent wilting point or PWP) to 31%. Wind tunnel experiments verified that nitrogen can be conserved either by heavy initial rain events (showing no NH3 volatilization with application of 2.5 cm rain immediately after urea application) or by banding of urea at a depth of 2.5 cm. Losses were maximized by maintaining adequate moisture in the topsoil for urea hydrolysis without inducing leaching, either by humidifying the air between 80 and 95% or by applications of 8 mm rain every 3 d. Increasing wind velocity from 1.7 to 3.4 ms−1 reduced NH3 loss from 19 to 7.5%, likely due to more rapid drying of the soil surface.

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