Freeze-Damaged Wheat Responding to Warmer Temperatures
Much of the winter wheat crop in Nebraska escaped significant injury from the freezes that occurred from April 3 to April 9. The lowest temperature — 7° F — occurred at North Platte the morning of April 7. At Beatrice the low on April 7 was 16° F and on April 8 it was 13° F. As we mentioned in an earlier CropWatch, winter wheat development was up to two weeks ahead of normal at the time of the freeze. The major reason for the advanced development was the warm March. At UNL's West Central REC rainfed farm near North Platte this was the warmest March since records were started in 1907. This year March was 9.6 degrees warmer than average.
Where wheat plants were injured, regrowth has begun in most situations. This is from both uninjured secondary tillers and from basal tillers. It is still too early to determine the amount of injury to winter wheat unless it was killed. We have often been surprised by winter wheat's ability to recover from injury.
It is difficult to estimate the yield potential when the primary tillers are killed and replaced by secondary and even basal tillers. Where the secondary tillers are healthy and number three to five per plant, do not expect more than 50-75% of the yield potential of the crop before the freeze.
If the winter wheat has to start over from the basal tillers, yields will likely be comparable to spring wheat. Since the crop will be much later, it also will fill much later and likely be exposed to high temperatures, which will shorten the filling period and reduce yield.
A few years ago, in a test plot at Grant, the well fertilized plots had more and larger heads with more kernels but the plants were later. Hot weather hit and the unfertilized plot, which was further along in filling when the heat hit, had the highest yield.
In conclusion, if the regrowth is coming from basal tillers, do not expect a higher yield than you would with spring wheat. In general, in Nebraska, spring wheat yields of more than 25 to 30 bushels are uncommon.
In the Gage County area in southeast Nebraska about 10% of fields appear to be a total loss with yields of less than 30 bu/ac. In some fields, where growing points appear dehydrated and the stem below the growing point is badly damaged, plants are just starting to collapse.
In western Nebraska, where most of the state's wheat is grown, the crop was not significantly injured by the freezing temperatures in early April. As this wheat continues to develop, however, it will be more susceptible to future freezing temperatures.
Robert Klein, Extension Crops Specialist
West Central REC, North Platte
Extension Educator, Gage County
Drew Lyon, Extension Dryland Cropping Systems Specialist
Panhandle REC, Scottsbluff