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Soil Science Society of America Journal Abstract -

Evaluation of Urea-Urea Phosphate as a Nitrogen Source for No-tillage Production1


This article in SSSAJ

  1. Vol. 51 No. 1, p. 242-246
    Received: May 19, 1986

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  1. W. J. Urban,
  2. W. L. Hargrove,
  3. B.R. Bock and
  4. R.A. Raunikar2



Urea-urea phosphate (UUP), a combination of urea and phosphoric acid, has properties which reduce the potential for NH3 volatilization but has not been evaluated extensively under field conditions. The objective of this study was to evaluate UUP (34-17-0) under laboratory and field conditions. All experiments were conducted on acid sandy soils typical of the predominant Ultisols found in the southeastern USA. A forced-draft technique was used to make direct measurements of NH3 losses in a growth chamber and also in the field. In addition, UUP and six other N sources were compared for no-till grain sorghum (Sorghum bicolor L. Moench) production. Direct measurement of NH3 losses in the growth chamber resulted in small losses from UUP on both mulched and bare soils, while NH3 losses from urea ranged from 15 to 32% of the applied N on a bare soil and 68 to 82% on a mulched soil. Direct field measurement of NH3 losses from urea, UUP, and ammonium nitrate applied at 200 kg N/ha were 19, 5, and 2% of the applied N, respectively. In the field plot studies, UUP compared favorably with ammonium nitrate and calcium nitrate with respect to crop response. The mechanism of NH3 loss prevention appears to be pH buffering by the phosphoric acid component of UUP. It is concluded that UUP is an effective N source for surface application to noncalcareous soils under no-tillage management.

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