Potassium deficiency

Potassium deficiency
Tom Zabadal , MSU Horticulture

Potassium is important for grapevines to function and is one of the most frequent nutritional deficiencies of vines. A grapevine with inadequate potassium produces poor, unevenly ripened fruit and reduced yields. Severe deficiency results in defoliation. Leaves in the mid- to basal portions of shoots are affected. Clusters of deficient vines tend to be small with a few unevenly ripened berries. Shatter of berries occurs in extreme cases. The relationship between another reported symptom, “black leaf,” and potassium deficiency is in doubt. Leaf petiole testing can reliably confirm potassium deficiency.


Leaf symptoms may begin in mid-June. Leaf margins turn yellow (left) and progress so that leaf margins become brown (right) and the tissue around the veins blackens. Photos: T. Zabadal

Additional information

Sampling information from MSU Soil and Plant Nutrient Laboratory

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in collaboration with MSU Extension and the Michigan Agricultural Experiment Station.
Updated 11/29/07 Contact: J.N. Landis.