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Responses of Six Crop Species to Solution Zinc²⁺ Activities Buffered with HEDTA

Department of Soil and Environmental Sciences, Univ. of California, Riverside CA 92521

*Corresponding author (dparker{at}mail.ucr.edu).

ABSTRACT

Zinc contamination has long hampered the use of conventional nutrient solutions for attaining reproducible and severe Zn deficiencies. Chelator-buffered solutions show promise for precisely imposing micronutrient deficiencies, but further studies are needed to fully evaluate the method and to develop methods to avoid Zn-deficiency-induced P toxicity. In a greenhouse study, seedlings of maize (Zea mays L. ‘Golden Cross Bantam’), wheat (Triticum aestivum L. ‘Yecora Rojo’), tall wheatgrass (Elytrigia pontica [Podp.] Holub ‘Orbit’), alfalfa (Medicago sativa L. ‘Germain's WL-320’), soybean (Glycine max [L.] Merr. ‘Vinton 81’), and tomato (Lycopersicon esculentum L. ‘Jackpot’) were grown for 16 to 29 d in solutions containing 0.4 to 12 µM total Zn. Computed Zn²⁺ activities were buffered at 4 to 123 pmol L^–1 by a 50-µM excess of HEDTA, and solution P was maintained at 10 ± 3 µM. Zinc deficiencies ranged from mild to severe, dry matter yield minima ranged from 32 to 89% of controls, and critical Zn²⁺ activities for the onset of deficiency ranged from approximately 10 to 65 pmol L^–1. The relative sensitivity of the six species to low Zn was maize > tomato > wheat > alfalfa tall wheatgrass > soybean. Shoot Zn concentrations were consistent with the widely reported critical range of 15 to 20 mg kg^–1. Zinc deficiency in the three grass species led to hyperaccumulation of P to phytotoxic levels, and leaf symptoms largely reflected this toxicity. Leaf P concentrations in the three dicots tended to be lower, but may have been within the phytotoxic range. Thus, even with P concentrations that approach soil solution values, the P toxicity that often accompanies Zn deficiency in solution-culture experiments was not eliminated. The effects of Zn deficiency on shoot concentrations of nutrients other than P were variable, although divalent cations tended to be elevated in Zn-deficient shoots.

Received for publication February 2, 1996.

This article has been cited by other articles:

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