As the Kansas wheat crop begins to break dormancy, concerns of winterkill are on the minds of producers. Two sub-zero events this winter with little to no snow cover may have frozen some wheat plants to death.
In most areas it is still too early to determine damage but when a polar vortex strikes with little to no snow cover, especially combined with poor soil moisture, the risk of damage is high. While snow cover saved some areas from the freeze, Central Kansas lacked the protective white blanket for the extreme cold temperatures.
“The wheat crop is currently more fragile than we would like because of drought and cold temperatures,” said Aaron Harries, director of marketing for Kansas Wheat.
Winter came earlier than expected this year leaving less time for wheat plants to develop before entering dormancy. Plants that are poorly developed going into winter, with few secondary roots and no tillers are more susceptible to winterkill.
Risk of winterkill is often determined by how low soil temperatures get at the crown level of the plant. Dry areas are most susceptible to the cold as soil moisture can help soil retain heat, protecting the crop. The air temperature above the soil may be 5 to 10 degrees but in moist soil the temperatures can remain 20 to 25 degrees above zero.
The ongoing drought has caused low topsoil moisture, increasing the risk for winterkill. Topsoil moisture supplies as of Jan. 27 were rated 48 percent very short, 37 percent short and 15 percent adequate.
Producers are advised to contact their crop insurance representative before making any management decisions on fields that have suspected winterkill injury.
Jim Shroyer, Kansas State University extension agronomist suggests if large areas of the field have winterkill but other areas are fine, it is best to avoid applying topdress fertilizer to the area where the wheat has died.
Plants that are killed outright will not turn green as the weather warms. Damaged plants will begin to green up then go backwards and die. There are enough nutrients in the crown to allow these plants to green up, but the winter injury causes vascular damage so the nutrients that are left cannot move, or root rot diseases move in and kill the plants. Shroyer says that this slow death is probably the most common result of winter injury on wheat.
However, wheat is a hearty crop, built to withstand winter’s storms. Last fall temperatures fell gradually, allowing the wheat crop to develop good winter hardiness. If the weather had gone from warm to extreme cold in a day, there would be more cause for worry.
“One general rule is that producers should not make any quick decisions about the condition of their wheat crop after a freeze,” writes Shroyer in this week’s agronomy eUpdate. “It will take several days of warm weather following freezes to evaluate the condition of the crop and its yield potential. Even if some of the main tillers are injured or killed, producers should wait to see if enough other tillers have survived to compensate for the lost yield potential. Patience is key.”
For a successful wheat crop weather conditions need to remain moderate throughout the next few months with an increase in rainfall.