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Foliar Fertilizer Damage to Corn Leaves: Relation to Cuticular Penetration¹

Foliar fertilization with N, P, K, and S has been reported to sometimes produce large yield increases in important food crops. However, zero and negative effects on yields are often reported: frequently in conjunction with foliage damage from fertilizer salts. Little is known about the mechanism of burn damage induction or the comparative damaging effects of different fertilizers applied to intact leaves.

We have compared the damaging effects of solutions of several N, P, K, and S fertilizers applied to intact corn (Zea mays L.) leaves under controlled conditions. Minor differences in the chemical structure of the fertilizers had large effects on the threshold concentration above which damage was induced. For example, K₂HPO₄ was damaging at concentrations 0.05 M whereas KH₂PO₄ became damaging only at concentration 0.50 M Penetration of these two compounds through the intact cuticle occurred at similar rates and was dependent on concentration rather than type of salt. Transfer away from the site of application was slow and significant differences in transfer rate were not observed. We conclude that all osmotically-active fertilizer compounds can induce plasmolytic damage when sufficiently high concentrations penetrate into the leaf. However, fertilizers such as K₂HPO₄ and some others with a higher range of solution pH have specific toxic effects which can induce cell and tissue necrosis at relatively low concentrations.

Key Words: N, P, K, and S salts • KH₂³²PO₄ • K₂H³²O₄ • Toxic and plasmolytic mechanisms • Zea mays L.

² Senior lecturer in plant physiology and graduate research assistants, respectively.

Received for publication January 26, 1981.