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This article in AJ

  1. Vol. 79 No. 3, p. 535-540
    Received: June 19, 1986

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Volatilization of Ammonia from Granular and Dissolved Urea Applied to Turf grass1

  1. Steve Titko III,
  2. John R. Street and
  3. Terry J. Logan2



Urea, applied in either granular or dissolved form, is a commonly used N fertilizer source for turfgrass, and volatilization of NH3 produced by urea hydrolysis is considered to be a major contributor to reduced N fertilizer utilization by established turf. Ammonia volatilization losses from urea applied to turfgrass were studied in a controlled environment chamber. Kentucky bluegrass (Poa pratensis L., var. Merion) sod was placed on a Crosby silt loam soil (fine, mixed, mesic Aerie Ochraqualfs) in 17.5-L plastic containers with surface areas of 434 cm2. Covers fitted to the containers had intake and exhaust ports such that air could be passed over the sod and NH3 collected in a boric acid trap. Experiments were conducted to examine the effects of temperature, relative humidity, wetting and drying cycles, and irrigation on NH3 loss from surface-applied urea. Ammonia losses were higher from granular than from dissolved urea in all cases, except where urea application was immediately followed by a 25.4-mm irrigation: Ammonia loss from granular and dissolved urea increased as temperature increased from 10 to 22.2°C, but there were no significant effects on NH3 loss as temperature increased from 22.2 to 32.2°C. Ammonia losses from dissolved urea at 68% R.H. were greater than losses at 31% R.H., but NH3 loss from granular urea was not significantly affected by relative humidity. Ammonia losses increased rapidly following periodic wetting of the turf fertilized with dissolved urea. Irrigation (25.4 mm) following urea application decreased NH3 losses from both dissolved and granular ureas.

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