Will the Recent Cold Temperatures Hurt Winter Wheat?

Unfortunately, this is the third time I’ve written an article about potential freeze damage to winter wheat this year. Previously, the concern was not high; however, as the wheat crop progresses toward heading and flowering, freeze damage becomes much more concerning.

The magnitude of freeze damage depends on: 1) temperature, 2) duration of exposure, and 3) wheat growth stage. A few years ago, we conducted a freeze chamber experiment to examine the effect of low temperature on winter wheat at several growth stages. At beginning flowering (Feekes 10.5.1), we saw a 10% reduction in wheat yield when temperatures reached 28°F for a 15-minute duration. Under field conditions at the University of Kentucky, researchers found a 41% yield reduction when temperatures were ≤30°F for six hours and less than 28°F for three hours at the heading stage (Knott and Raymond, 2020). (Wheat at Feekes 8 had no yield penalty.) These cited freeze thresholds are risk benchmarks, with other factors such as microclimate, soil moisture, and weather conditions after the freeze event all influencing wheat yield potential. According to the CFAES Weather System (https://weather.cfaes.osu.edu/), low air temperatures ranged from 31.6 to 32.6°F at the Western Agricultural Research Station in Clark County. However, temperatures at Piketon Station in Pike County were ≤30°F over a four-hour period.

Figure 1. Wheat spikelets and awns may appear white or bleached as a result of freezing temperatures. (Photo: Douglas Alt, 2020)

Assessing potential yield losses in winter wheat after a freeze event is challenging. At heading and flowering, wheat spikelets and awns may appear white or bleached (Figure 1). At the University of Kentucky, visual damage after a severe freeze event was only 23% while yield reductions were 41% (Knott and Raymond, 2020). Extent of damage to winter wheat may not be apparent until kernel development.

For more information, see our ‘Freeze Symptoms and Associated Yield Loss in Soft Red Winter Wheat’ FactSheet: https://ohioline.osu.edu/factsheet/anr-93

Reference:

Knott, C.A., and Raymond, C. (2020). Wheat yield reduction when freeze occurs during heading. Crop, Forage & Turfgrass Management, 6, e20070. Available at: https://acsess.onlinelibrary.wiley.com/doi/10.1002/cft2.20070