Troubleshoot pale-green corn

Corn is V6 to V8 and looks good on tiled fields but is pale green on nontiled fields. We applied 180 pounds per acre of preplant anhydrous N and 30 pounds of N in row starter. How could it be deficient in nitrogen? What can we do?
This month’s Indiana certified crops adviser panel includes Danny Greene, Greene Crop Consulting, Franklin; Abby Horlacher, Nickle Plate Consulting, Frankfort; Brian Mitchem, Farmer 1st Agronomy Consulting Services, Decatur; and Dan Quinn, Purdue Extension corn specialist.
Greene: My first thought is low sulfur. We’ve seen where N was present but sulfur deficiency caused the pale color. The imbalance could slow corn growth. Low zinc could be involved, or somehow nitrogen could be reduced.
Work with your crop adviser to take plant samples and soil samples in good and poor areas. Include micronutrient analysis. Run a pre-sidedress nitrogen test (PSNT) to show nitrate and ammonium nitrogen levels.
Because tiled fields are OK, look at soil drainage. Maybe roots haven’t reached preplant N bands. Once, a client used two anhydrous ammonia applicators, and one placed ammonia deeper, resulting in slower green-up. Yet sometimes shallower N placement can cause root burn and weaker plants. Plants could also appear pale if wet conditions restrict roots.
If sulfur is low, consider Y-drop application of ammonium thiosulfate or broadcast ammonium sulfate over the top. If N is lacking and soils are sealed, a pass with an anhydrous applicator applying a low N rate might increase oxygen and kick-start the crop.
Horlacher: This sounds like roots live in an aerobic environment and don’t take up nutrients well. The 210 pounds of nitrogen is usually sufficient. Take a PSNT and a nitrogen mineralization test to see how much nitrogen is available. This will indicate if nitrogen was lost from either application. A tissue test would assess nitrogen in plant tissue.
If soil nitrogen is sufficient, wait a week for drying and see if corn comes out of it. If not, a foliar application could help. Try a manganese sulfate product. If N is low, make an additional sidedress application.
Mitchem: With 210 pounds N applied, corn is unlikely deficient in N between V6 and V8 despite wet weather. It is possible for N loss due to denitrification to limit corn at later growth stages. Denitrification occurs when soil is saturated and microorganisms convert nitrate to a gas.
Get a snapshot of limiting nutrients with a tissue test. Consider a soil nitrate test too, and discuss results with a CCA. Plan a course of action, which might include applying additional N.
In the future, consider moving preplant N to sidedress and include a nitrogen stabilizer on wet soils. Reducing early sidedress rate and adding another layer with Y-drops would help.
Quinn: Tissue-sample plants to assess nutrient levels. Just because plants are pale green doesn’t always mean it’s a nitrogen issue. Find areas of greener plants to sample and compare. Even though nitrogen was applied, fields with poor drainage and flooding can still lose nitrogen through denitrification.
Changing nitrogen timing to include row starter and more in-season nitrogen applications may help. Time nitrogen application closer to plant uptake. Nitrification inhibitors, although not silver bullets, can help with nitrogen loss.
Apply a couple of different N rates to assess if a higher nitrogen rate is required on nontiled fields.