NC State Extension Publications

Problem

Nutritional disorder – potassium (K) deficiency

Symptoms

Older leaves initially develop a tanning or darkening coloration along the outside leaf margin. As symptoms develop, the dark discoloration spreads between the veins. With advanced symptoms, the entire leaf can become necrotic. In addition to leaf symptoms, darkening of the petiole also occurs. Over time, the entire leaf dies.

Plants size is typically smaller. Fruit color appears pale, can be less flavorful and the texture can be more pulpy.

Initial symptoms of potassium deficiency on the lower leaves.

Initial symptoms of potassium deficiency on the lower leaves.

Brian E. Whipker

Intermediate symptoms of potassium deficiency.

Intermediate symptoms of potassium deficiency.

Brian E. Whipker

Intermediate symptoms of potassium deficiency.

Intermediate symptoms of potassium deficiency.

Brian E. Whipker

More advanced symptoms of potassium deficiency.

More advanced symptoms of potassium deficiency.

Brian E. Whipker

Severe symptoms of potassium deficiency.

Severe symptoms of potassium deficiency.

Brian E. Whipker

Severe symptoms of potassium deficiency - whole plant view.

Severe symptoms of potassium deficiency - whole plant view.

Brian E. Whipker

Similar Problems

Deficiencies of magnesium, sodium toxicity, drought stress and wind damage may produced similar symptoms.

Additional Information

Because symptoms can occur due to many possible causes, it is important to determine the actual cause. Tissue testing will help identify any nutritional disorders. Reviewing the weather history and growing conditions will help to determine if that is the cause. It is also useful to note that weather related problems will be more prevalent over a wider area of the field and can develop quickly. Nutrient deficiencies usually take weeks to develop.

Diagnostic Tips

Take a soil sample to determine if nutrient levels are inadequate. Submit a leaf sample for nutrient analysis. The sufficiency range for potassium in strawberries is between 1.5 and 2.5%, although some published sources indicate the range can be 1.1 to 2.5%. Depending on the reference, values lower than 1.1 to 1.5% can lead to deficient conditions. Levels above 2.5% are considered excessive.

Corrective Measures

Take a soil and tissue test to determine nutrient levels. Make adjustments based on those test results and the lab’s recommendations.

Management

Conduct a soil test prior to planting the crop to determine if pre-plant fertilizer applications are required. Fertilizer can also be injected to the crop during active growth. Recommendations vary by soil type and your location, so check with local resources for guidelines.

Funding Sources

Funding was provided in part by the National Sustainable Agriculture Program: Sustainable Strawberry Initiative and the following sources.

A thank you is also expressed to Kube Pak of Allentown, New Jersey for donating strawberry plants.

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Author:

Professor
Department of Horticulural Science

Publication date: April 23, 2014

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