Influence of texture and ph of kaolinitic soils on zinc fractions and zinc uptake by peanuts
1993
DAVIS-CARTER, JESSICA G. | SHUMAN, LARRY M.
High soil Zn concentrations can cause Zn toxicity in peanuts, which diminishes productivity and can be fatal to plants. The objectives of this study were (i) ot determine the interactive effects of soil texture, pH, and Zn rates on the distribution of Zn among fractions in kaolinitic Coastal Plain soils, and (ii) to relate soil Zn fractions to Zn uptake by peanut (Arachis hypogaea L.) plants. Four soils were selected for this study: Lakeland sand, Tifton loamy sand, Greenville sandy clay loam, and Greenville sandy clay. Zinc sulfate was applied at three rates (0, 20, and 40 mg Zn/kg soil), and limestone was applieid at four rates to each soil in a factorial design. Peanut plants were grown in a greenhouse for 10 weeks. Duplicate soil samples were fractionated for Zn by a sequential technique. Total Zn was determined by digestion with HF, HCI, and HNO3. The sum of Zn fractions was not significantly different from the total soil Zn. The percentage of Zn in the exchangeable and organic matter faractions was higher in the coares-textured soils, and the percent in the crystalline Fe oxide fraction was greater in the fine-textured soils. Application of Zn increased the amount of Zn in the soluble forms, specifically, the exchangeable, organic matter, and Mn oxide fractions. Liming redistributed Zn from the exchangeable fraction to less soluble fractions. The amount of Zn in the exchangeable fraction was best correlated with CEC, but the sum of fractions was best correlated with the clay percentage. Plant Zn concentrations were most highly correlated with the exchangeable fraction. Because of toxic Zn effects, plant weight was lower at high Zn availability, which led to positive correlations of plant weight with Zn in the relatively plant-un-available forms.
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