Irrigation strategy during heatwaves: Softening the blow

by | Mar 1, 2024 | South Africa Wine Scan

All over the world, vineyards are subjected to extreme heat events during the ripening period, and irrigation is a way of mitigating the negative effects of these heat spikes. A three-year Californian study evaluated the impact of three different irrigation strategies pre – and during heatwaves on grapevine physiology, berry chemistry and wine quality.


Project layout

The trial was conducted on a commercial Cabernet Sauvignon block grafted onto Paulsen 1103. The three irrigation treatments were applied pre- and during heatwaves and described as baseline treatment, baseline × 2 and baseline × 3. The baseline treatment was deficit irrigated using 60% evapotranspiration (ET). Baseline × 2 received double the amount, and baseline × 3 received triple. The differential treatment started one or two days before the heatwaves and continued until the end of the heatwaves.



  • The amount of irrigation applied significantly affected yield and the chemistry and sensory properties of the resulting wine.
  • The baseline treatment resulted in reduced gas exchange, higher leaf temperature and lower evaporative cooling, while no differences occurred in the 2× and 3× treatments.
  • Anthocyanins, tannins, pH, and acidity were negatively affected with baseline treatment and also the 3× treatment.
  • The baseline treatment had the highest TSS and lowest yield.
  • No significant impact on carbohydrates was recorded during the study period.


Significance of the study

This study highlights that under- and over-irrigating during heat waves can harm wine quality. When a deficit irrigation strategy is utilised throughout the season in a high-quality grape production environment, a change in tactics is required when forecasts point towards imminent heatwaves. Irrigating closer to or just above 100% of ET pre- and during heatwaves appears to be an effective mitigation.


Elisabeth FORRESTEL, Martina GALEANO, James CAMPBELL, Sophia BAGSHAW, Morgan FURZE, Luis SANCHEZ, Nick DOKOOZLIAN, Annegret CANTU, Andrew GAL, Mallika NOCCO, Andrew McELRONE, (2023). Heatwaves impacts on grapevine physiology, berry chemistry & wine quality. IVES Conference Series, GiESCO 2023.


Image: Pixabay

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