Many farmers are taking a closer look at their corn fields and finding a variety of crop challenges as we approach physiological maturity.
One common visual symptom is the firing of the corn plant or expression of a nitrogen deficiency. Look for a V-shaped area moving down the midrib of the corn leaf, first appearing on the lower part of the stalk since nitrogen is a mobile nutrient in the plant.
If the supply of nitrogen entering the plant with soil water is inadequate to meet the developing ear’s demand, the plant will remobilize nitrogen from the older tissues of the lower leaves and stalk and move it to the developing ear. Significantly affected plants exhibit leaf necrosis (tissue death) up to and including the ear leaf. Other plants may show only deficiency symptoms on the lower leaves, if at all.
The expression of nitrogen deficiency is well documented and easy to identify but the cause of the deficiency can be much more elusive. It is worth the time to determine contributing factors to each field’s lack of plant-available nitrogen as we make plans for the 2012 crop.
One common cause of nitrogen deficiency in areas missing all the rain events is dry soil. Since most of the plant-available N is in the nitrate-N form and moves in the soil by mass flow (with water), the amount of N getting into the plant is closely related to the amount of plant-available soil water and the concentration of nitrate-N in the soil water.
If soil water is limited, so is the avenue for nitrate-N to get into the plant. Although there may be an adequate amount of N applied to sustain good plant growth, if it is not in the nitrate-N form or in soil solution, it will be positionally unavailable to the plant resulting in expression of a N deficiency.
The return of soil moisture through rainfall will help transport the nitrate-N to the plant. Unfortunately, during periods of extended hot, dry weather similar to what many Illinois farmers experienced in July and much of August, an inadequate supply of N may result in a significant loss in harvest yield.
Corn plants that have lost yield potential but have regained a late-season N supply to sustain growth may exhibit a reddish-coloration. Although yield has been limited, sugar production through photosynthesis continues, producing sugars that have no place to go. As simple sugars accumulate in leaf tissue, the pigment anthocyanin overcomes the green color produced by chlorophyll, resulting in the reddish (purple) color development.
What is the best way to minimize a lack of N available caused by dry soils? Visit with your local FS Crop Specialist for his solution. It works.