DEHARDENING OF WINTER WHEAT AND RYE UNDER SPRING FIELD CONDITIONS
Changes in cold hardiness (LT50), fresh weight, dry weight and moisture content were measured on crowns of winter wheat (Triticum aestivum L.) and rye (Secale cereale L.) taken from the field at weekly intervals in the spring of 1973 and 1974 at Saskatoon, Sask. In all trials, Frontier rye came out of the winter with superior cold hardiness and maintained a higher level of hardiness during most of the dehardening period. For cultivars of both species, rapid dehardening did not occur until the ground temperature at crown depth remained above 5 C for several days. Changes in crown moisture content tended to increase during dehardening. Over this same period crown dry weight increased for winter rye but did not show a consistent pattern of change for winter wheat. Two test sites were utilized in 1974. One site was protected by trees and the other was exposed. General patterns of dehardening were similar for these two sites, but cultivar winter field survival potentials were reflected only by LT50 ratings for the exposed test site. The influence of fall seeding date on spring dehardening was also investigated. Late-seeded wheat plots did not survive the winter in all trials. However, where there was winter survival, no differences in rate of dehardening due to seeding date were observed.