Vineyard Frost Protection
Passive Methods for Managing Frost
Passive frost protection methods are used to avoid frost danger, rather than protect against a frost occurrence. Generally passive methods do not offer the same degree of protection as active methods but do not cause significant increases in establishment costs for most vineyards. Passive protection methods can be divided into those which are done prior to vineyard establishment and those which are done after vineyard establishment.
Prior to Vineyard Establishment
The best time to protect a crop from frost is before it is planted. The importance of a good site selection in the long term sustainability of a vineyard operation cannot be over emphasized. For more information on selecting a suitable site for growing vines go to Chapter 4, Vineyard Site Selection.
Variety selection can influence the incidence and severity of spring frost damage. Varieties, which have early bud burst and development, are usually more susceptible to spring frost damage than varieties with late bud burst and development (See Table 27.1).
Vineyards with timberline of trees, overgrown fence rows, highway and railway embankments, buildings located on the down slope side of the vineyard can form a frost pocket, even though the site is elevated or has a slight slope.
After Vineyard Establishment
After the vineyard has been established, other passive protection methods can be used to minimize the effect of frost damage. Some examples include soil management, canopy management, pruning, and cover crops.
Both moisture and compaction improve thermal storage capacity and conductivity of the soil. Bear, compacted wet soils store more heat by day and then re-conduct heat by night rather than loose, dry soils. Typically, under these conditions the temperature can increase by up to 1 to 2 degrees F (0.6 to 1.1°C) above the minimum temperature in the vineyard.
Trellis Height/Canopy Management
There is a greater risk of frost damage with trellis systems where the buds or shoots are located closer to the ground.
One of the easiest and most practical ways to avoid frost damage in the vineyard is to use a grapevine’s natural growth habit. This can be done by employing a number of pruning techniques that take advantage of a characteristic that all grapevines have called apical dominance. This term simply means that the buds on the tip of a cane will grow first, and the buds at the base of a cane, closest to the trunk, will grow last.
Double Pruning: Double pruning involves removing only those canes that will not be used for fruiting or a source of spurs.
Delayed Pruning: A general recommendation for grapevines grown in a spring frost prone areas is to delay pruning as late as possible and to prune lightly in the spring.
Cover crops reduce the amount of heat absorbed by the ground during the day and inhibit the release of heat at night. Cover crops also create roughness and can slow the movement of air, causing cold air to build up rather than moving off the vineyard.
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