Potassium, K, promotes general vigor, disease resistance and sturdy growth. Potassium deficiency causes stunted growth with leaves close together. Starting with the older leaves, the leaf tips and edges turn scorched brown and leaf edges roll. Excess potassium may cause calcium and magnesium deficiencies. Calcium, Ca, is a major ingredient in cell walls and is important for root growth, especially root tips.
Calcium deficiency causes poorly developed roots with weak tips.
Leaves are distorted with hooked tips and curled margins. Magnesium, Mg, is vital to chlorophyll production and is important in most enzyme reactions. Magnesium deficiency causes different symptoms in different plants, but commonly includes leaf yellowing with brilliant tints. Leaves may suddenly drop off without withering. Symptoms show first on older leaves.