Magnesium deficiency always shows initially on the older leaves. Chlorosis develops between the veins, while a narrow area on each side of the veins remains green. The leaf margins - and with proceeding deficiency also the intercostal areas - become necrotic.
Made worse by
Sandy soils. Acidic soils. Potassium rich soils. Soils receiving high potash applications. Cold wet periods.
Better crop establishment. Reduced plant losses over winter. Increases nutrient levels in the crop for better spring regrowth. Improved flowering. More even maturity. Boosts grain yield and oil content of seed.
Magnesium deficiency Fe and Mn deficiency also show intercostal chlorosis and necrosis, but the symptoms start on younger leaves.