It’s been a quiet year so far regarding wheat, so it didn’t surprise me when the calls started rolling in this week regarding wheat looking yellow. Most wanted to know if we had disease issues out there. Looking at fields throughout Nuckolls and Clay counties, I saw very little disease overall. That’s most likely due to the dry conditions we’ve had and the fact that many fields I looked at were wheat on corn or soybean stubble. Wheat on wheat fields had disease such as tan spot or septoria leaf blotch on the leaves. I did not see any powdery mildew or rust in any of the fields I looked at.
So why are some fields yellow? Well, most likely it’s due to a combination of factors. We had a dry fall and winter. Some wheat had winter injury and some just never developed a good root structure due to lack of moisture. Dr. Drew Lyon, UNL Extension Dryland Cropping Systems Specialist, also shared with me that poor root structure could also be a result of not having a firm seed bed during planting. Without a firm seed bed, roots aren’t allowed to develop like they should, can’t explore the soil for nutrients, and are more exposed to the potential for crown and root rots. Fall-applied fields often had sprayer wheel
tracks showing green wheat in the wheel tracks and yellow wheat elsewhere-most likely the compaction from wheels allowed for better establishment, created a depression where moisture held, and allowed for less nitrogen loss.
Fall applied nitrogen may have been lost due to the dry fall and winter. It appears that fields with spring applied nitrogen look better due to moisture this spring after application. There’s also environmental reasons for yellow wheat. The cold soil temperatures may not have allowed for nitrogen release to the plants yet-we may see a change by next week. Many places in south central Nebraska have experienced dry conditions creating yellow-brown lower leaves and a blue cast to the wheat. I have pictures of wheat with ice crystals on it from some of the cold snaps we experienced. Cell rupture of that plant tissue could also have caused the yellowing of those lower leaves.
Bottom line, right now there’s nothing you can really do for the yellow wheat and warmer temperatures may allow for nitrogen uptake in the future if the nitrogen wasn’t already lost. Right now there’s nothing to be worried about regarding fungal disease concerns. I’d recommend you continue scouting your fields for powdery mildew and rust and consider a fungicide application if needed (need to protect the flag leaf). I’ll keep you updated on what I’m finding in the fields!