Magnesium plays an important role in photosynthesis as the center of the chlorophyll molecule and acts in enzyme reactions forming proteins, and aiding the plant in the manufacture of energy. Uptake in the corn plant is greatest at the V5 growth stage.
Deficiencies of magnesium in corn can cause reduction in growth and are most common on sandy, acidic soils. The symptoms will appear first on the older leaves. Additionally, high rates of K fertilizer without an Mg source can induce a deficiency so applying a balanced fertilizer like Intrepid Trio that has K, Mg, and S in each granule will keep your corn field balanced with the nutrients it needs to continue to produce high quality grain.