Vinay Pagay,* Felipe Canela, and Felipe Canela
*University of Adelaide, PMB 1, Glen Osmond, Australia (vinay.pagay@adelaide.edu.au)

Knowledge of grapevine water use is vital for efficient irrigation management in vineyards so that irrigation volumes match crop water demand. Over two growing seasons, 2019-20 and 2020-21, we used custom-built, whole-canopy chambers to estimate the daily water requirement of mature grapevines (Vitis vinifera L. cvs. Chardonnay and Shiraz [syn. Syrah]) grown in a hot climate of South Australia. Environ- mental conditions, soil moisture, and vine water status (midday stem water potential) were measured simultaneously and crop evapotranspiration (ETc) was calculated using the Penman-Monteith relationship for comparison with the whole-canopy measurements. In the second season, heat pulse velocity (sap flow) sensors were installed in the sentinel vines, calibrated with the canopy chambers, and used to provide continuous vine transpiration estimates from budbreak to postharvest. Our results indicate that mature, fully-irrigated grapevines in the field used 12 to 17 L water per day during the peak of the summer. Vine water use measured with the chambers represented 22% and 28% of seasonal irrigation applied on Chardonnay and Shiraz vines, respectively. Vine water use was also estimated at ~60% of ETc. Daily dry matter production of Chardonnay and Shiraz grapevines were ~200 g/day and 150 g/day late in the season, between veraison and harvest. Sap flow sensors indicated that vine water use during heatwaves, when daily maximum temperatures exceeded 35°C for three or more days, increased by 13% and 7% (compared to both pre- and post-heat- wave periods) in Chardonnay and Shiraz, respectively. Canopy water use efficiency was greatest early in the morning, perhaps due to the relatively greater proportion of diffuse light at that time. Whole-canopy gas exchange chambers coupled with calibrated sap flow sensors have proven to be a valuable tool for quantification of plant water use and therefore, irrigation scheduling in vineyards.

Funding Support: Wine Australia, Riverland Wine