Frost damage to winter wheat in the UK: the effect of plant population density

Abstract

One winter wheat variety, Soissons, suffered extensive frost damage in a plant population density (PPD) and sowing date (SD) experiment in 1997/1998. Another variety, Cadenza, did not incur any frost damage, even though it was at a similar developmental stage to Soissons when the damaging frosts (minimum grass temperatures of −8 and −9 °C) occurred. Therefore, in addition to rapid development, other physiological characteristics of Soissons, such as the presence of awns and weak glaucosity must be important in determining its susceptibility to frost damage. When sown on 23 September, the low PPD crops suffered the most frost damage but when sown on 25 October the high PPD crops suffered the most. This challenges the assumption that low PPDs are more resistant to frost than high PPDs. No frost damage was observed in the crop sown on 16 December. Frosts killed spikelets, restricted internode extension (stem growth) and reduced yield. Frosts in April and May, after growth stage (GS) 33, appeared responsible for the damage symptoms observed in the crop. Minimum temperatures in April and May were similar to those recorded in the previous season when no frost damage was observed. There had been a cooler winter in 1996/1997, allowing slower crop development and more cold hardening, therefore the frosts in the spring of 1997 did not inflict obvious damage.