A FIELD TEST FOR ASSESSING THE WINTER HARDINESS OF ALFALFA IN NORTHWESTERN CANADA

Abstract

A procedure is described for separating differences in winter hardiness among alfalfa (Medicago sativa L.) cultivars under field conditions. The procedure depends upon two factors associated with winterkill in northern Alberta during the 1977–1978 winter, namely, low food reserves in the crowns resulting from improper cutting management plus cold stress due to lack of snow in early winter. To induce these conditions we recommend that year-old plants be clipped in mid-June, late July and early September and that snow be removed once from the plot during early winter on the first day that air temperatures below −30 °C are forecasted. Natural snow fall can protect the plot for the remainder of the winter. If soil temperatures do not drop close to the range of the LT50 of the control cultivars, snow cover may be removed again provided air temperatures are below −30 °C. Cultivar rankings for winter hardiness following severe stress induced by snow removal were significantly correlated (r = 0.944**) with the mean survival observed at five locations following natural winter stresses in this region. Although additional work is warranted, the induced stress procedure has real merit in screening winter-hardy genotypes in the field and in assessing management techniques to reduce the effects of stressful winter environments on alfalfa production in northwestern Canada.Key words: Alfalfa, winter hardiness, field test, snow removal, frequent clipping