Areas of yellowing wheat are showing up in fields across North Carolina… from the Piedmont to the Tidewater. With all the rain we’ve had it is likely that most of these problems are related to a deficiency in leachable nutrients with sulfur being the most likely culprit. Potassium and nitrogen may also be suspects.
A sulfur problem will usually result in the upper younger leaves turning yellow in contrast to a N problem that results in yellow lower - older leaves.
Should remedial fertilizer applications be made now? There is probably no 100% correct answer to that question. The closer we get to heading, the less likely fertilizer applications are to result in yield benefits. However, if the crop is suffering from nutrient deficiencies, and is somewhere between early jointing and early boot stage, it seems logical and preferable to do something to green it back up!
What options are there? A diagnostic tissue sample from the yellow and green areas is always a good idea! Most of the phone calls I’ve had so far have been S problems, and the most common prescription has been granular ammonium sulfate. Other granular options are possible as well for turning a S problem around. If the problem is related to a micronutrient, a tissue test will help to determine that.
Remember that liquid fertilizers such as UAN or 24S applied after jointing can burn the leaves and developing grain head inside the stem. For that reason these forms of liquid N or S are generally not applied at this growth stage. Tank-mixing UAN or 24S liquid fertilizers with fungicides and/or insecticides can in some cases make this burn worse. So, dry fertilizer is the safest option.