Magnesium activates more enzyme systems than any other nutrient and serves as a component of chlorophyll. Magnesium availability is often related to soil pH as its supply to plants decreases in both low and high pH soils. Although soils supply varying amounts of Mg naturally, soil reserves are depleted in many areas due to continued cropping without Mg-containing fertilizers or dolomitic limestone.
Symptom Description — Since Mg is a mobile nutrient in plants, deficiency appears first on older leaves as yellowing or interveinal chlorosis. Increased severity of the deficiency can cause the symptoms to appear on younger leaf tissue with the development of necrotic symptoms when the deficiency is very severe. Leaves may become brittle or thin, and cup or curve upwards. Tips of leaves may become reddish-purple in cases of severe deficiency.