Potassium deficiency causes yellowing and scorching or older leaves.  These symptoms begin at the margins of the leaf and spread between the veins towards its centre.  Large areas of tissue around the major veins remain green until the disorder is well advanced.  A brown scorch develops in the yellow areas and spreads until the leaf is dry and papery.  Potassium from a fertilizer side-dressing will move from the soil surface to the roots only if the soil is very sandy.  Potassium fertilizers are therefore best incorporated in the soil before planting.  Fertigation or drip feeding can also be used to treat a deficient crop.

Foliar spray of Kcl 1% at weekly interval.