Phosphorus deficiency causes reduced growth and small leaves that drop early, starting with the oldest leaves. Leaf color is a dull, bluish green that becomes purplish or bronzy. Leaf edges often turn scorched brown. Excess phosphorus may cause potassium deficiency. 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.