New winegrape research looking at irrigation levels has produced some positive results for growers in coastal areas of California. Lead author of a research paper that was recently published, Kaan Kurtural said their work shows promise for future irrigation strategies. Kurtural and his team studied the impact of various irrigation approaches at a research vineyard in Napa Valley over two seasons.
“We found out that winegrapes can get by with 50 percent of the evapotranspiration demand in the coastal areas,” Kurtural noted. “There was a good happy-medium at this replacement rate with the fruit composition. Meaning that we were optimizing the fruit composition from anthocyanins, to flavonols, to tannins without any significant loss in yield.”
Kurtural, who is an Extension Specialist and Professor of Viticulture and Enology at UC Davis, said they looked at water replacement levels of 25 percent and 50 percent. The winegrape research also included the measuring of carbohydrate content and evaluation of the fruit produced. Kurtural explained that they looked at the relationship the vines had with the endemic fungi in the soil. Upon evaluation, the vines irrigated at the 50 percent rate maintained a healthy soil profile. When compared to the “control vines” that received 100 percent of the water lost to evapotranspiration, the grapevines that received half the irrigation that would normally be used allowed the vines to maintain yield quantity and fruit quality.
“Having the knowledge at hand will be helpful for the growers. They were asking, ‘well, we’re at so many inches in deficit, should we over-irrigate this year to make up for the loss?’ But it doesn’t look like you need to with winegrapes. So, it’s a good finding moving forward,” said Kurtural. “You don’t necessarily have to give up the yield to get the quality with the reduced amount of water application.”