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This article in SSSAJ

  1. Vol. 51 No. 2, p. 366-370
     
    Received: May 23, 1986


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doi:10.2136/sssaj1987.03615995005100020020x

Efficient Nitrogen Use as Affected by Urea Application and Irrigation Sequence1

  1. J. C. Katyal,
  2. Bijay Singh,
  3. P. L. G. Vlek and
  4. R. J. Buresh2

Abstract

Abstract

On alkaline coarse-textured soils (Psamments) of Punjab, India, urea is applied after the irrigation event to minimize leaching and denitrification loss. However, placement of urea on the wet surface of alkaline soils promotes NH3 volatilization. This experiment compared (i) urea, (ii) urea plus dicyandiamide (DCD), a nitrification inhibitor, (iii) urea plus phenylphosphorodiamidate (PPD), a urease inhibitor, and (iv) potassium nitrate (KNO3) applied before or 20 h after the irrigation event. Grain yield of wheat (Triticum durum L. var. DWL5023) and N use efficiency were observed in a 2-yr study. During the first year all of the fertilizers were 15N labeled. Potassium nitrate gave the highest yield and maximum 15N recovery by the crop indicating that leaching and denitrification were not significant loss mechanisms. Grain yield was increased from 3.6 to 4.4 Mg ha−1 and loss of urea-N was reduced from 42 to 16% by applying urea just prior to irrigation compared to following irrigation. DCD did not alter the effect of fertilizer timing with respect to irrigation on 15N recovery or wheat yield. Urea applied with PPD yielded 0.4 Mg ha−1 more than urea alone when applied on wet soil. This suggests that NH3 volatilization was the major N loss mechanism. This study suggested that for higher N use efficiency and grain yield of wheat, urea should be topdressed before the irrigation event on the coarsetextured soils.

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