The fear of dilution: rainfall, irrigation and grape ripening

Many growers, wine makers, wine writers, and regulators do not like rainfall and irrigation during grape ripening, because they fear the water will “dilute” the quality of the grapes. This presentation discuss recent research by his group, which has demonstrated that grape berries control their own size and concentration by changing the inflow and outflow of water.

The beginning of ripening (veraison) is marked by a steep increase in sugar, and hence water, inflow to meet the demand of the berries. This enables the berries to ripen even under drought stress conditions If the air is warm and dry enough, the berries dispose of the excess water by evaporating it across the skin. Under humid conditions, however, they recycle the water back to the leaves.

The data used, supported by field trials, show that drip and sprinkler irrigation during the ripening stage do not cause qualitative dilution of the grapes; however, rain and sprinkler irrigation, or even very humid weather conditions, not only block evapotranspiration from the berries, but also lead to water ingress from the skin.

This video shows the OPENING SEMINAR of the 10th edition of Enoforum (May 16th-18th, 2017, Vicenza, Italy).