Between the R2 and R3 stage, the corn has take up about 75% of the nitrogen for the season. During this time I am often asked “Is my crop running out of nitrogen?”
One common confusion is that many of the symptoms shown in the lower canopy of healthy corn, where there is not a lot of sunlight anymore, falsely resemble a true nitrogen deficiency.
Normal Re-mobilization Nitrogen Deficiency Vs True Nitrogen Deficiency
Even when corn has the optimal nitrogen levels, it’s normal for the very bottom leaves to die off. The corn has out grown those leaves because sunlight cannot reach them anymore. The nitrogen nutrients mobilize and move to the more effective leaves, higher in the canopy.
When taking a closer look, these normal re-mobilization nitrogen deficiencies differ from true nitrogen deficiencies. First, it only effects the very bottom leaves, the next leaf up will be fully green and healthy. Also, you wont see the classic yellow inverted v down the center of the leaf that comes with true nitrogen deficiency. What you will more likely see is just a yellowing on the outside of the leaf that moves it’s way inward.