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Agronomy Journal Abstract -

Growth and Root Morphology of Corn as Influenced by Nitrogen Form


This article in AJ

  1. Vol. 84 No. 4, p. 694-700
    Received: Jan 11, 1991

    * Corresponding author(s):
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  1. R. H. Teyker  and
  2. D. C. Hobbs
  1. A gricultural Research Dep., National Fertilizer and Environmental Research Center, TVA, Muscle Shoals, AL. 35660.
    P fister Hybrids, P.O. Box 186, El Paso, IL 61704.



Public concern about NO-3 levels in potable waters, together with improving techniques for maintaining NH4+ availability in soils, has renewed research interest in the effects of N form on crop growth. The effects of NO-3 versus NH+4 on growth and morphology of juvenile corn (Zea mays L.) were investigated in two experiments. In Exp. 1, 16-d-old, solution-grown plants produced less shoot fresh weight when grown with NH+4 than with NO-3 nutrition. Root fresh weights were similar, but elongation of the primary root axis and its longest first order lateral was less with NH+4 nutrition. Under NH+4 nutrition, apparent thickness (grams per meter) of primary roots was 54% greater, and the frequency of first order laterals with second order laterals was 65% greater, than under NO-3 nutrition. In Exp. 2, plants were grown in the greenhouse until 40 d after emergence in a slightly alkaline 3:1 sand:soil mix. Nitrogen (75 mg N kg−1) was supplied as either Ca(NO3)2 or (NH4)2SO4 plus nitrapyrin [2-chloro-6-(trichloromethyl) pyridine]. Ammonium-grown plants produced 2.3 times the dry matter and had higher concentrations of N in both stems (18.5%) and leaves (27.5%) compared to NO-3- grown plants. Tillering was increased by NH+4- 4 nutrition. Apparent root thickness was again greater under NH+4 nutrition, but the difference between N regimes was only 15%. Results indicate that under conditions of course-textured soils and slightly alkaline pH an enhanced NH+4- N regime may be advantageous for growth of corn. Differences in pH regimes between the hydroponic and soil-based experiments may account for the contrasting results

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