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Fertilizer burn occurs when chemical fertilizers (which are composed of salts) are applied at high concentrations. Although all vegetables can be affected by fertilizer burn, cucurbits are particularly sensitive because they do not have a thick waxy cuticle on their leaves. Therefore, they do not shed water as well as some other vegetables, such as onions or the Brassica species. When the water containing the fertilizer evaporates from the leaves, all that is left is the fertilizer salt, which can quickly desiccate (dry out) the leaves, leading to fertilizer burn. Seedlings are very tender and are particularly sensitive. Symptoms include a generalized burned appearance or flecking resembling a spray pattern.

Fertilizer burn to cucumber seedlings.

(Photo: Timothy Coolong, University of Kentucky)

Management:

• Avoid foliar feeding if possible; care should be taken when it is necessary. Compared to roots, the leaves are capable of taking up only small quantities of fertilizer.
• When using a water-soluble fertilizer in the greenhouse, growers may want to rinse the fertilizer off the leaves.
• Growers should plan on providing all the necessary fertility for their crops through fertigation or soil applications.

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