Sap flow meters and dendrometers, measuring tiny changes in trunk diameter, have been installed at two Riverina vineyards to monitor stress in shiraz, cabernet sauvignon, merlot and chardonnay above 40 degrees Celsius. 

Heat stress can lead to fewer leaves, burnt grapes and a lower yield. 

NSW DPI viticultural development officer Adrian Englefield said the study aimed to identify the point where vines could benefit from better irrigation decisions.

“Any reductions in sap flow during extreme weather events, compared with baseline measurements, can indicate vine stress,” he said. 

Tamburlaine Organic Wines vineyard manager Clayton Kiely applauded the methodology and said the results would help vignerons in Orange, although he wanted to see the study extended to a cool climate region.

“Our water usage is about one-tenth of what they use in the Riverina,” he said.

“They get heat days right through the seasons so they’re more acclimatised whereas our vines are happy with cooler temperatures so they’re not used to seeing the huge fluctuations we’re getting and they can shut down.”

Mr Kiely said he had needed to irrigate during the severe heatwave conditions in recent days to ensure moisture in the soil compensated for the heat and wind. 

Live data from the heatwave management project is available online here.