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Cold resistance adjustments of field-hardened winter wheats as determined by artificial freezing

Suneson, C.A., Peltier, G.L.
Agronomy journal 1934 v.26 no.1 pp. 50-58
Triticum aestivum, mortality, air temperature, rain, variety trials, freezing, winter hardiness, cold tolerance, Nebraska
Controlled freezing experiments at progressive 2-week intervals from early November to late March with field-grown plants are reported. An increase in hardening, as expressed in the ability of wheats to endure lower temperatures, was shown from November to January, followed by a nearly equal recession in hardiness from January to late March. Marked and statistically significant changes in the relative hardiness rank of the varieties used, Blackhull, Kawvale, Nebraska No. 60, and Minturki, were noted during the winter. These changes are attributed to hardening adjustments. Exposure to severe temperatures was essential for maximum expressions of cold tolerance, but exposures to specific hardening temperatures did not always result in the same hardiness relationships, which suggests an important role for other environmental and seasonal factors in the hardening phenomenon. The demonstration of changing relative varietal relationships under a field environment may permit an explanation of the fairly frequent abnormalities associated with localized field trials and may account for some of the inconsistencies experienced in laboratory evaluations with field plants. More precise information is needed concerning the factors influencing the hardening process, but investigators can not be cautioned too strongly against a general application of results based on any one particular period or on any one specific field condition.