Cold survival of winter wheat
How do severe temperatures impact winter wheat? According to Bob Fanning, South Dakota State University Extension Plant Pathology Field Specialist, the current winter wheat crop in South Dakota is doing well because it either received enough moisture early on in its development or it was planted into protective cover, protecting it from the recent extremely low temperatures.
Fanning explained that winter wheat planted early into adequate moisture or receiving moisture from October precipitation was able to grow, produce a few leaves and maybe a tiller or two, and because both high and low temperatures for the day tapered off fairly gradually, the early planted wheat was able to harden off before the recent below zero weather occurred. As for the late planted wheat, Fanning explained that although it has barely emerged, the majority of late planted wheat was planted into protective cover, which should temper severe dips in soil temperatures.
“Moist soil is not as vulnerable to the severe temperature swings that can occur in dry soil, creating a more favorable environment,” Fanning said. “Winter wheat plants containing adequate moisture are also better able to survive the stresses of winter than those under moisture deficit.”
He added that soil temperatures can be a good indicator of the potential for winterkill of the wheat crop.
“Most of the winter wheat varieties grown in South Dakota have fair to good ratings for winter hardiness, and can withstand temperatures at the crown level as low as 0-5 degrees when properly hardened off and with adequate moisture,” he said.
Although air temperatures have dipped well below zero several times over the past week or so, for the most part, Fanning reminded growers that soil temperatures have remained in at least the teens, even at the 2-inch level at some of the coldest locations in the state.
“This is very typical, as soil temperatures fluctuate much more slowly than do air temperatures. Protective residue further protects the soil from lowering in temperature compared to bare ground, and if that residue is able to trap and hold snow, soil temperatures fluctuate even less,” Fanning said.
To learn more about winter hardiness ratings on winter wheat varieties, visit iGrow.org and access the “Winter Wheat Variety Trial Results” at igrow.org/ agronomy/wheat/winterwheat-variety-trial-results/.
Fanning added that although conditions can certainly deteriorate, for the time being, the winter wheat crop should be surviving the winter well.
“As we know from past history, a cold period in late winter or early spring after a warm spell that brings the wheat out of dormancy often causes more winterkill than low temperatures during the winter,” he said. — WLJ