Preliminary evalution of artificial snow cover as a method for the protection of the vine during winter in Québec

The sensitivity of the vine to cold temperatures makes it a high risk crop in Québec. Winter colds during January and February can reach through the course of several days - 30° C and consequently the intense cold can damage the buds. However, during this same period, the snow cover normally present on the ground insures a certain protection to the aerial portions of the vine by insulating them from the intense cold air dominating the surface. Moreover, given the random character of the snowfall regime, vine growers must in addition ridge the vine stocks to protect them from the cold. This research work discusses artificial snow making as a method of protection for the vine and addresses one of the major problems faced by this type of culture under extreme climatic conditions. Temperature measurements were recorded over four experimental plots during the cold season in a vineyard in Québec. A plot covered by artificial snow for protection against the winter cold was compared with three others, one with a natural snow cover, one with a leaf cover and covered by natural snow and one covered by natural snow with fine ice crusts following snowfalls. Results show that during the major colds of January and February, the vine shoots located at 30 cm from the ground and protected by artificial snow conserved much higher negative minimum temperatures, by as much as 23°C compared to the vine shoots located at the same height on the other plots. Results also reveal that a snow cover of 15 to 20 cm is sufficient to insulate entirely the vine shoots from the ambient air. Hence, the use of artificial snow cover is an efficient method of protection against the cold. However, when using artificial snow covering in the fall while the natural snow cover is still absent, non crystallized water penetrates the ground down to the root zone through percolation and reduces the temperature by approximately 3°C down to a depth of 30 cm. In the same manner, in relation to traditional methods of protection, during spring the early thawing of the snow cover at the center of the ridges leaves the vine shoots without protection and exposes them to late frosts. Other results relating to the use of artificial snow for covering stocks with regards to bud mortality rate and fruit yield in the fall should permit the evaluation of the real impact of this method on stock productivity and the quality of production.