MANHATTAN, Kan. - Wheat in Kansas that did not have snow cover during a cold snap the first week of January suffered some injury to its foliage, said Jim Shroyer, K-State Research and Extension wheat specialist.
Leaf injury from cold weather while the wheat is dormant will not affect yields, however, since wheat begins new growth from the crown in the early spring, he said. The bigger question is whether temperatures were cold enough to injure the crown itself, which is typically about a half-inch deep in the soil. As long as the crown survives, the wheat will remain alive.
"Winter wheat can survive cold temperatures well as long as soil temperatures at the depth of the crown are not in the single digits for a prolonged period of time," Shroyer said.
"Winter wheat typically has its highest level of winter hardiness in December and January," he said. "Leaves on wheat exposed to very cold temperatures may turn brown and die back somewhat, but that doesn't necessarily mean the entire plant is dead. Soil temperature is a more important consideration than air temperature alone during the winter."
In most cases so far, soil temperatures have not been cold enough to create concern for the wheat, Shroyer said. However, there are areas of concern, especially where soils are dry. For example, soil temperatures at the 2-inch depth reached 9 degrees on Jan. 5 at Scandia, in Republic County.
Will this cause some winterkill in those areas?
"It's too soon to know, but the situation should be monitored - especially on terrace tops and north-facing slopes. I wouldn't be surprised if there is some damage to the wheat in parts of north central Kansas where soil temperatures were this low," he said.
Producers shouldn't necessarily be concerned if wheat remains brown this winter and doesn't start greening up as daytime highs get into the 40s and 50s, Shroyer said. That's not warm enough for wheat to start greening up.
To know if the wheat is still alive, producers could dig up some plants and bring them inside. After a week or so of warm conditions and water, wheat should begin greening up if it is alive, he said.
"Otherwise, producers can wait until spring greenup begins in the field. Areas of dead or dying wheat should be noticeable at that time," the K-State agronomist said.
If plants are killed outright by cold temperatures, they won't green up in the spring. But if they are only damaged, it might take them a while to die, Shroyer said.
"They will green up and then slowly go backwards and eventually die. There are enough nutrients in the crown to allow the plants to green up, but the winter injury causes vascular damage so that nutrients that are left cannot move, or root rot diseases move in and kill the plants. This slow death is probably the most common result of winter injury on wheat," he said.
Direct cold injury is not the only source of winter injury. Under dry soil conditions, wheat plants may suffer from desiccation. This can kill or weaken plants, and is a more common problem than direct cold injury, he said.