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This article in SSSAJ

  1. Vol. 51 No. 1, p. 124-128
    Received: May 21, 1986



Comparison of a Forced-draft Technique to Nitrogen-15 Recovery for Measuring Ammonia Volatilization Under Field Conditions1

  1. W. L. Hargrove,
  2. B. R. Bock,
  3. R. A. Raunikar and
  4. W. J. Urban2



Reliable field measurements of NH3 volatilization are necessary for evaluating N-fertilizer efficiency for sod crops and conservation crop production systems. This study was conducted to compare NH3 loss measurements under field conditions using a forced-draft technique and recovery of urea-15N. Measurements were made from urea solution applied at a rate of 100 kg N ha−1 to a bare or mulched Cecil sandy loam soil (Typic Hapludult). In an adjacent area, microplots were established to which urea enriched with 15N was added. Ammonia losses from the bare and mulched soil were 49 and 72% of the applied N by the forced-draft technique, and 14 and 46% of the applied N by 15N recovery. The air flow rate with the forced-draft technique was shown to exceed the actual wind speed near the soil surface 10 and 50% of the time for bare and mulched soil, respectively. These results raise serious questions about the validity and accuracy of the forced-draft technique. The usefulness of the forced-draft technique may be limited to relative comparisons of N sources, N rates, and various management practices.

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