Amanda de Oliveira Silva, Small Grains Extension Specialist
Weather forecasts indicate that temperatures will continue to drop in the next few days. The extent of possible damage from these below-normal temperatures on wheat will depend on several factors such as wheat developmental stage, soil moisture, snow cover, field conditions, and how cold and for how long these cold weather stays.
Most of the wheat in Oklahoma was dormant or just starting to come out of dormancy before this extreme cold front came in. The more advanced in growth the wheat is, the more exposed the growing point is and susceptible to injury. On the other hand, wheat fields planted late in December are also vulnerable as the wheat may not have had the time to develop its crown roots and tiller to sustain these cold temperatures. The most important part of the plant is the crown at this moment. We may see leaf damage, but if the crown remains alive, the plant can survive. Figure 1 provides a general guide to the minimum temperature threshold and its impact on yield. Keep in mind these temperature thresholds are not exact but provide a decent rule of thumb. Temperatures closer to the soil surface might be higher than those reported by weather stations one meter above the soil surface, especially if moisture is present.
Except for the western OK and Panhandle regions, most areas of the state were with adequate soil moisture, which helps to insulate the crop and improves survival chances. Also, if we receive the snow cover that is forecasted, the wheat will be more protected from the harsh conditions.
Regarding my last post that some varieties may have reached first hollow stem (FHS). Growers should keep in mind that FHS is based on the largest tiller on the plant. Even if we lose the largest tillers, we are fine as long as other tillers are viable and we have favorable growing conditions.
Each freeze event is unique. It will take some time (1-2 weeks after the cold weather passes) to assess the actual impact of the below-normal temperatures on wheat. We will have to keep watching it as it will vary on a field-by-field basis.
Contact your local county Extension office.
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