Keeping vineyards cool – and grape quality high – during heatwaves

Decades of research and grower experience have transformed how winegrape growers manage their vineyards during heatwaves to prevent crop losses through berry shrivel.

Wine Australia has drawn together the pertinent science and knowledge into factsheets and other extension materials, and supported the dissemination and uptake of best practice through its nationwide Regional Program.

The very high temperatures experienced during the 2009 heatwave in southeastern Australia saw vines being defoliated and grapes suffering sunburn and heat damage. Ripening was temporarily delayed, harvest intake schedules were thrown into disarray, and there were large losses (in many cases at least a quarter of the crop) due to shrivelling because vines couldn’t supply enough water to the fruit.

Increasing soil organic carbon by mulching during winter and spring enabled growers to increase their soil’s water-holding capacity so that it could retain soil moisture during summer. Growers also modified their irrigation systems and practices because irrigating during hot-weather events was ineffective.

Moving to irrigation systems that allow short, frequent applications provided more control and more flexibility to get the water where it was needed, when it was needed. Irrigating according to soil type also meant that water was used more efficiently with the result that less water was used but it was used more strategically.

By irrigating vines before hot-weather events, growers were able to manage record hot days in January 2019, where temperatures reached 46°C, and achieved improved resilience and yield. Instead of the 25 per cent losses that were experienced in 2008, losses were contained to 9 per cent, equivalent to an overall improvement of $400–500 per hectare.