Impact of Severe Freeze on Commercial Soft Red Winter Wheat Varieties in the Mid-Atlantic.

Soft red winter wheat is affected by freezing temperatures depending on variety, maturity date and growth stage at the time of the freeze. Variety and injury specific information related to freeze severity is lacking in the literature. North Carolina experienced a significant freeze March 10th thru 17th, 2017. Two variety trials containing 57 commercial varieties each replicated 5 times were evaluated for yield losses from this freeze event in Union and Rowan counties. Below freezing temperatures occurred for 52 and 92 hours, respectively. A representative 0.3 m of row was collected from each variety to evaluate total number of tillers, damaged stems, dead flag leaves, normal stems, damaged heads, undamaged heads and kernel number per head. Yield potential before the freeze event, yield loss as a result of the freeze and yield potential following the freeze event were calculated using gathered metrics. Plots were harvested with a Wintersteiger Delta plot combine. Yield potential estimates after the freeze event were compared with actual yield data. The Rowan location was at an earlier growth stage at the time of the freeze (Zadoks 28) and recovered more than the Union location which was at a later growth stage (Zadoks 45). Early maturing varieties realized an average of 71% of estimated yield potential, medium maturing varieties 60.7%, and late maturing varieties realized only 55.9% of yield potential at Union County, NC. In Rowan County, NC, early maturing varieties realized an average of 96.5% of estimated yield potential, medium maturing varieties 108%, and late maturing varieties realized only 110.3% of yield potential. Results from these trials will allow us to better assist growers during and after future freeze events to make more accurate estimates of yield loss and total yield potential. Growers may also use this information to make better variety selections for their operations.