Source: Jim Shroyer, Kansas State University Extension agronomy state leader
There have been several reports of damaged leaves and some stunting of wheat in recent weeks. In most if not all of these cases, the wheat was no-tilled into heavy soybean residue, planting depth is shallow, and root development is poor. The damage became much more apparent quickly during a brief period of very warm and windy conditions in early April.
There are at least three possible causes of this:
a) The wheat growing in heavy surface residue conditions suffered more freeze injury from the cold temperatures on March 20-22. Leaf tip damage from that injury is still apparent. In addition, the shallow seeding depth and poor root development had made the wheat much more susceptible to environmental stresses. Excessive drill speed is often a factor in shallow planting.
b) Poor root development, due to shallow planting, soil compaction, and/or saturated soils, is the primary factor in making the wheat susceptible to sudden hot windy weather.
c) Winterkill damage to the crown and vascular system of the wheat occurred, making this wheat more susceptible to environmental stresses.
The most likely explanation, in Jim Shroyer's opinion, is (a). Most of what he's seen so far has been leaf damage typical of early-season freeze injury. He has not yet seen true drought stress, although the period of hot, windy weather set the wheat back.
Also, where there is less residue on the soil surface, the wheat looks much better at this time. This wheat did not have as much freeze injury on March 20-22 because the warmth of the soil was able to radiate upward and provide more protection to the plants.
The second-most likely explanation is (b). Certainly we are seeing poor root development, and this could easily result in considerable drought stress shortly if conditions become unusually hot and windy in April. But as of now, this has not yet happened in most areas.