The impact of low winter rainfall on grape and wine composition

Recent research has demonstrated the relation between winter rainfall and vegetation growth, and its implications for grape and wine composition.

This interesting Australian paper, which has received the ASVO Best Oenology Paper Award 2022 (Australian Society of Viticulture and Oenology), highlights the importance of spring and winter soil water availability in defining wine style, and establishes a framework for the adoption of irrigation strategies to maintain the wine style of that particular region in a context of changing climate. Indeed, according to the authors, climate change will alter the wine styles of a given region if new practices are not adopted or existing practices are revised both in the vineyard and in the winery.

Studying Shiraz vineyards located in the Barossa region of Australia, different irrigation strategies were evaluated over three seasons in a vineyard where winter rainfall was excluded using rain hedges to mimic the possible extreme conditions we can expect from climate change. Irrigation was applied to complete soil profiles either during winter or during budbreak and all treatments were compared to vines receiving average winter rainfall.

Results showed that a reduction in winter rainfall by about one-third of the historical average had a major impact, reducing yield by up to 40 percent. Yield was partially restored with irrigation, but it had effects on vine balance and grape and wine composition. When soil moisture was restored during budbreak by natural rainfall or by additional irrigation, as opposed to progressive soil wetting during winter, the vines developed denser vegetations and the concentration of phenolic substances was reduced in the fruit and wine.

The ASVO article is available at this link