Is it too much water? Growing sweet corn and it's about 20 inches tall. Lower leaves are turning yellow. Well draining soil, and I water 3 times a week. I fertilized at 6 inches tall with side dressing. This is a fast growing yellow variety (Northern Xtra Sweet Yellow sh2 Hybrid 67 days) especially for northern regions, as I live in northern Michigan.
Corn Leaves Turning Yellow
Certified GKH Gardening Expert
Yellowing leaves generally indicates a watering issue, either to much or to little.
Sweet Corn does have a shallow root system so I would add another watering. Every 3 days, but certainly increase if the temps are above 85 degrees or the soil is drying to much between waterings.