Potassium deficiency (K)
Purpling and later necrosis of leaf margins in particular. Plants are more susceptible to lodging and tend to senesce earlier.
Treatment: K deficiency is difficult to treat curatively and the emphasis should be on achieving and maintaining an adequate supply from the soil.
Note that although K removal is quite modest at around 40–50kg K2O/ha, the crop takes up over 200kg/ha and this must be accounted for. Korn-Kali® with 5% S is an excellent choice for preventive applications, as the contained sulphur is fully water-soluble and is therefore immediately available to plants.