Question: The corn in this area (southern MN) looks very good, but I have noticed some plants have developed purple leaves on the mid to upper portions of the plant. What is this? And should I be concerned about it for next year’s corn?
Answer: I would say you may be observing the result of a phosphorus deficiency in your corn. If severe enough, you will see spiraling of the corn kernel rows occur. Along with the potential for a phosphorus deficit in your corn, bear in mind that nearly anything that restricts root growth has the potential to cause corn leaves to purple. I would be concerned about identifying the exact cause of the purpling so you know exactly what you’re dealing with and can take some actions to prevent it next year, if need be. Soil and tissue tests would be a good investment for you to consider.
Soil pH is key to phosphorus availability because if soil pH is too high or too low, the nutrient will not be available to the plant
Pest injury becomes evident above ground as areas of yellow and stunted plants develop. Sometimes purpling of the leaves indicates a phosphorus deficiency, along with browning of the leaf tips and edges.