Potassium deficiency (K)
Symptoms of potassium deficiency are not easily detected in citrus plants. These symptoms will initially appear on older leaves, as chloroses and subsequent necroses on leaf tips. Leaves will appear wrinkled, and will later roll in. Fruit are small, with very thin skins, and have a tendency to take on colour prematurely.
It is advisable to conduct a calculation of fertilizers requirements, which should be based on the results of a soil analysis and on the actual crop requirements. A lack of potassium during the vegetation period may be remedied by foliar application of potassium sulfate in the form of a specialty fertiliser, such as HORTISUL®, In case of fertigation, preference should be given to using sulfatic fertilisers as potassium sources (HORTISUL®).