Potassium Deficiency of Grape
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Potassium deficiency is a common problem since potassium is utilized in large amounts by grapevines. Mid-shoot leaves develop a dull, dark-green color (often called ‘black leaf’), which progresses to basal leaves on older shoots. Interveinal chlorosis and marginal necrosis (browning, tissue death) may occur; in severe cases, necrotic areas may expand across leaves.
Interveinal and marginal chlorosis caused by potassium deficiency.
(Photo: Kaan Kurtural, University of Kentucky)
Management:
- Apply foliar sprays of potassium nitrate or potassium sulfate to temporarily alleviate deficiency symptoms.
- For long term correction, apply bands of potassium sulfate or potassium nitrate beneath the canopy (within the dripline); rate should be based on soil tests.
- Excessive potassium levels may result in magnesium deficiency.
