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This article in AJ

  1. Vol. 91 No. 2, p. 287-293
    Received: Jan 21, 1998

    * Corresponding author(s): goos@badlands.nodak.edu
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Response of Spring Wheat to Nitrogen Fertilizers of Different Nitrification Rates

  1. R. Jay Goos*,
  2. Julie A. Schimelfenig,
  3. Bert R. Bock and
  4. Brian E. Johnson
  1. N atl. Fertilizer and Environmental Res. Ctr., Tennessee Valley Authority, Muscle Shoals, AL
    D ep. of Soil Science, North Dakota State Univ., Fargo, ND 58105



Hydroponic and greenhouse studies have shown that grain yields of wheat (Triticum aestivum L.) are maximized when the N supply contains a mixture of NH4 and NO3. Tillers per plant is the yield component most commonly increased by mixed N nutrition in greenhouse studies. The objective of this study was to evaluate, under field conditions, the response of ‘Butte 86’ spring wheat to N sources differing greatly in nitrification rate. Nitrogen was applied at 0 or 112 kg N ha-1; the N sources were calcium nitrate (CN), urea, ureadicyandiamide (DCD), 0.1-g urea granules, and 0.1-g urea-DCD granules. Six field trials were performed. Topsoil (0–15 cm) analysis of fertilized plots during tillering indicated a wide range of mineral N contents (19–101 mg N kg-1) and of NH4:NO3 mole ratios (0.04–2.06). Correlation analyses suggested that tillering was sensitive to the total mineral N supply, but quite insensitive to the NH4:NO3 ratio in the topsoil. Vegetative growth and N uptake were generally lower for CN than for the other N sources. At some locations, more heads per square meter at harvest were observed with the slower-nitrifying N sources. Grain yields were increased by N fertilization, but significant differences between N sources were not generally observed. For both years of the study, the 0.1-g urea-DCD granules gave the highest N uptake efficiency. However, the dramatic responses in growth, tillering, or grain yield routinely observed with mixed N nutrition in hydroponic or greenhouse studies could not be duplicated in the field.

Research supported by the North Dakota Agric. Exp. Stn. and the Tennessee Valley Authority.

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