The primary phosphate deficiency symptom is reduced growth and dark-grey necrosis of the lower leaves of the plant. The primary potassium-deficiency symptom is yellowing, with large necrotic patches on the oldest leaves. Sulphur deficiency may occur in many soils and in any area of the province. A soil test is recommended to establish the available sulphur status of fields. The primary sulphur deficiency symptom is a general chlorosis of the plant, with the youngest leaves showing a greater degree of yellowing than the older leaves.
Sunflowers take up and remove modest levels of nutrients compared to barley or canola.
Germinating sunflower seeds are sensitive to fertilizer placed with the seed. When sunflowers are seeded with row equipment, all phosphate and potash should be sidebanded two inches beside and below the seed at time of seeding. Some or all of the nitrogen may also be sidebanded. Nitrogen requirements not side-banded should be placed away from the seed as a band or broadcast application. Table C. Phosphorus, potassium and sulphur recommendations for sunflower based on soil test levels and placement.