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This article in AJ

  1. Vol. 90 No. 6, p. 740-746
     
    Received: May 18, 1997


    * Corresponding author(s): wtes2@aeneas.net
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doi:10.2134/agronj1998.00021962009000060004x

Foliar Feeding of Cotton: Evaluating Potassium Sources, Potassium Solution Buffering, and Boron

  1. Donald D. Howard ,
  2. C. Owen Gwathmey and
  3. Carl E. Sams
  1. Plant and Soil Sci. Dep., Univ. of Tennessee, P.O. Box 1071, Knoxville, TN 37901

Abstract

Abstract

Foliar applications of K may be used to supplement soil applications to maximize yields of cotton (Gossypium hirsutum L.). Response to foliar K applications may be improved by choice of K source, buffering the spray solution, or applying K with B. Research was conducted on a Collins silt loam (coarse-silty, mixed, acid, thermic Aquic Udifluvents) and on a Memphis silt loam (fine-silty, mixed, active, thermic Typic Hapludalfs) to evaluate KNO3, K2SO4 K2S2O3, and KCl as K sources. A second study evaluated foliar KNO3 and K2SO4 solutions applied unbuffered and buffered to pH 6 and 4 on cotton K nutrition and yield. Foliar K in both studies was applied at 4.1 kg K ha−1 per application. A third study evaluated combinations of soil-applied and foliar-applied B and K. Foliar treatments were applied in 93.5 L ha−1 water at early flower or 2 wk after and repeated on a 9- to 14-d interval between the four applications. Yields from the four K sources averaged 10% higher than the untreated check and yields with KNO3 were 4% higher than the other K sources. Buffering two K source solutions to pH 4 resulted in 10% higher yields than the check or unbuffered K solutions. Adding a surfactant (ethoxylated alkyl aryl phosphate esters) to KNO3 resulted in 5% higher yields then the check. Compared with untreated check yields, soil-applied B at 0.56 kg B ha−1 increased yields by 6%, four foliar applications of 0.11 kg B ha−1 increased yields by 8%, and four foliar applications of 0.11 kg B plus 4.1 kg K ha−1 increased yields by 13%. Foliar K solution buffering and/or the inclusion of foliar B are relatively inexpensive ways of improving yield response. Based on yield increases in this study, these treatments should return 8 to 10 times the product costs.

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