Vine spraying: an effective technique against spring frosts

Spring frost poses a serious threat to vineyards, causing severe damage to buds and jeopardizing the harvest. In response to this risk, winegrowers have developed a variety of protection methods, among which sprinkling stands out as a particularly effective solution.

Understanding the phenomenon of frost in vineyards

Spring frost generally occurs between March and May, when buds begin to develop. There are two main types of frost:

• radiative freezing: occurs on clear, calm nights, when the ground loses heat through radiation

• advective frost: caused by the arrival of a mass of cold air, often accompanied by wind
  Buds can withstand temperatures down to -3°C, but beyond this, the risk of damage increases considerably. Frost can lead to the death of embryonic flower or leaf tissue, compromising future harvests.

The principle of sprinkling to combat frost

Aspersion involves spraying water on vines to protect them from frost. The technique is based on a physical phenomenon known as supercooling. Here’s how it works:

1. water is sprayed in fine droplets onto the vines

2. when water freezes, it releases latent heat

3. this heat maintains the temperature of plant tissue above the freezing point

4. a thin layer of ice forms around the buds, insulating them from the outside cold
   To be effective, spraying must be continuous for as long as temperatures remain negative. Generally speaking, between 30 and 50 m³ of water are required per hour and per hectare.

Advantages and disadvantages of sprinkling

Advantages and disadvantages of sprinkling

Advantages:

• Highly effective, offering reliable protection against frost at temperatures as low as -7°C

• Covers large vineyard areas, providing extensive protection

• Automatable system, reducing manpower requirements on critical nights

• Environmentally-friendly method, using only water with no chemical additives

• Adaptable to different plot types and soil configurations

• Can be used as a preventive measure as soon as night-time temperatures approach freezing point

Disadvantages:

• Requires substantial water resources, which can be problematic in areas subject to water restrictions

• High initial investment to install the sprinkler system throughout the vineyard

• Risk of overloading plants if the technique is poorly mastered, which can lead to damage to branches and buds.

• Potentially reduced efficiency in the event of advective frost accompanied by strong winds

• May require constant monitoring on frosty nights to ensure optimal operation

• Recurring operating costs related to water and energy consumption for pumping

The decision to adopt this method must be carefully weighed against the specific features of the vineyard, the frequency of spring frosts and the resources available. Although sprinkling offers many advantages for protecting vines against late frosts, winemakers should also consider other complementary techniques for a complete protection strategy.

The Ventigel system: an innovation in frost protection

Faced with the limitations of conventional spraying, new solutions have emerged. Among them, the Ventigel system stands out for its innovative approach.
Ventigel combines powerful ventilation and additional heat to protect vines from frost. It works in two main ways:

1. early ventilation: a powerful jet of forced air dries out the plots, preventing the formation of condensation on the plants

2. calories: an integrated heating system warms the pulsed air when temperatures continue to fall
   This mobile device can cover 2 to 3 hectares and can be adapted to different types of terrain thanks to its adjustable inclination. Electrically powered, Ventigel offers a more ecological and economical solution than traditional methods such as candles or straw fires.

Installation of a sprinkler system or Ventigel

To install a sprinkler or Ventigel system, several steps are required:

1. needs assessment: surface area to be protected, frequency of frost events

2. feasibility study: available water resources, site configuration

3. system sizing: number of sprinklers or Ventigel units required

4. installation: setting up the water distribution network or Ventigel units

5. testing and adjustment: checking that the system is working properly before the risk period
   It is advisable to call in professionals for the design and installation of these systems, to guarantee their effectiveness.

Protecting vines against spring frost is a crucial issue for winegrowers. Spraying, whether classic or innovative like the Ventigel system, offers an effective and increasingly affordable solution. Although requiring an initial investment, these techniques can save entire harvests and prove profitable in the long term. In the face of the challenges posed by climate change, mastery of these protection methods is becoming a major asset in sustaining wine production.

FAQ

How to protect vines from frost?
There are several methods to choose from: spraying, ventilation (such as Ventigel), antifreeze candles, antifreeze towers, or cable heating. The choice depends on local conditions and budget.

Why do vines freeze?
Vines are particularly sensitive to spring frosts because their buds start to develop early in the season, making them vulnerable to sudden drops in temperature.

How much does a vine antifreeze candle cost?
Antifreeze candles generally cost between €8 and €15 each. You need about 200 to 300 candles per hectare.

How much does an antifreeze tower cost?
An antifreeze tower can cost between €30,000 and €40,000. It can protect around 4 to 5 hectares.

How effective is an antifreeze wind turbine?
Antifreeze wind turbines can be effective down to -3°C or -4°C. Their effectiveness is highly dependent on weather conditions and terrain configuration.