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This article in SSSAJ

  1. Vol. 40 No. 3, p. 470-472
    Received: July 31, 1975



The Effect of Controlled-Availability Nitrogen Fertilizers on Mature Pecan Trees1

  1. D. T. Sullivan,
  2. G. A. O'Connor and
  3. E. Herrera-Aguirre2



Two controlled-availability N fertilizers, sulfur-coated urea (SCU) and NH4NO3 plus N-Serve, were compared with NH4NO3 alone applied to 30-year-old pecan trees (Carya illinoensis Koch) in a 2-year study. Leaf N contents were increased in both years by N fertilization, but yield and nut weight were not significantly affected. Yields in 1973 were correlated with 1972 leaf N contents, but not with 1973 leaf N contents. The SCU treatment was effective in controlling N release in 1973, but not in 1974. The N-Serve treatment was ineffective both years of the study. The ineffectiveness of the controlled N sources were attributed to: (i) poor incorporation of the materials, (ii) inherent slow response of mature pecan tree to N fertilization, and/or (iii) sufficient variability within treatments to mask fertilizer source difference.

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