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This article in SSSAJ

  1. Vol. 73 No. 6, p. 2177-2183
    Received: Nov 16, 2008

    * Corresponding author(s): apmallar@iastate.edu
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Assessment of Potassium Supply for Corn by Analysis of Plant Parts

  1. Antonio P. Mallarino *a and
  2. S.L. Higashibc
  1. a Department of Agronomy, Iowa State University, Ames, IA 50011
    b Formerly a graduate student assistant at, Iowa State University
    c Currently at, USDA Forest Service, 333 SW First Avenue, P.O. Box 3623, Portland, OR 97208


Tissue testing of corn (Zea mays L.) ear leaves often is used to diagnose K deficiencies. However, little attention has been given to study how testing of different corn tissues evaluates K supply especially in the optimum to excess range. We evaluated tissue tests for corn based on the K concentration of young plants (V5 to V6), ear leaves at silking, lower stalks at maturity (sections cut from 15 to 35 cm aboveground), and grain. Twenty-eight field trials were conducted in Iowa during 2 yr with fertilizer rates of 0, 56, 112, and 168 kg K ha−1 Initial soil-test K (STK) by the ammonium acetate extractant (15-cm sampling depth, air-dried samples) was 80 to 266 mg K kg−1 across sites. Fertilizer K increased grain yield at one site testing 84 mg K kg−1; and increased the K concentration of plants, leaves, stalks, and grain at 11, 13, 21, and 5 sites, respectively. Published critical K concentrations for corn plants and leaves would have incorrectly indicated deficient soil K supply for yield in many sites. There were upper limits in plants, leaves, and grain K concentrations response to K supply that varied among sites. The limits occurred at STK values of 123, 140, and 148 mg kg−1, respectively, which are near STK values optimum for grain yield. The lack of an upper limit in corn stalks shows promise for using this tissue to assess K availability from deficiency to luxury uptake or excess. However, the large site-dependent variability in the stalk K concentrations should be recognized as a limitation.

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