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This article in AJ

  1. Vol. 69 No. 6, p. 969-974
     
    Received: Sept 23, 1976
    Published: Nov, 1977


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doi:10.2134/agronj1977.00021962006900060017x

Critical Zinc Levels Related to Early Growth and Development of Determinate Soybeans1

  1. K. Ohki2

Abstract

Abstract

Evidence of Zn deficiency in determinate soybeans [Glycine max (L.) Merr.] has appeared. Critical deficiency levels of Zn relating leaf concentration and growth are needed to provide reference values associated with maximum growth. The objective was to determine reference values needed to aid in the Zn fertilization program. Soybeans were grown in the greenhouse for 41 days in modified Hoagland solution with total Zn rates of O, 5, 10, 20, 50, 100, 200, 300, 400, 500, 700, and 1,000 μg/liter Zn. Leaf blades were sampled at harvest and analyzed for Zn by atomic absorption. The critical nutrient deficient levels for Zn were 15, 15, and 14 μ/g dry weight in blades 1 (young developing leaf), 2, and 3 (recently matured leaf), respectively. For purposes of evaluating the Zn status, the recently matured leaf (blade 3) is suggested as the tissue to sample. The critical Zn levels in blade 4 and 5 were 17 and 21 μ/g, respectively. Blade 1 had the sharpest transition zone. Zinc deficiency reduced top and root dry weights, plant height, flower number, and branching; however node development was not affected by Zn deficiency stress. Symptoms similar to Mn toxicity were induced by very low Zn supply. High Mn concentrations were associated with low Zn in blade 3 of plants supplied with 5 μg Zn/liter.

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