Tillage considerably increases the risk of frost

Irrespective of the temperature, the phenological stage of the vine or the soil context of the block, 25% more relative humidity means 50% more frost damage and burnt buds”. Research engineer Guillaume Delanoue from the French Institute of Vine and Wine (IFV) in Amboise was categorical at a conference on weather hazards held during the Vinitech trade fair. “We have been observing this recurrently since 2016 and it is not a good thing because generally, in April, during frost spells, winegrowers start using tillage again to maintain the ridges as an alternative to chemical weeding”, he said.

Based on readings from several sensors installed in the vineyards of Chinon and Quincy, Delanoue showed that at the coldest times of the day, the relative humidity at the level of the buds in the machine-farmed plots is more than 30% higher than in the plots that are not farmed mechanically. And this is true for at least two days.

“The level is 98% compared to 65% the day after the implements were used, and 88% compared to 58% the day after”, he told the audience. “These figures vary according to the type of soil and the rainfall at the beginning of the year and in particular over the previous two weeks, but the humidity can make all the difference in the event of a very light frost”, he stressed, before explaining that eight days at more than 15°C are required for the machine-farmed plot to regain the humidity of the control plot. “It even takes 20 dry days when the rainfall was more than 20 mm during the 20 days prior to tillage”.