Reducing stress with overhead sprinklers during heatwaves

by | Jun 6, 2024 | South Africa Wine Scan

Heat waves are common during most seasons in many grape-growing regions. They negatively affect the quantity and quality of the crop, especially during water shortage periods. Proactive irrigation before these heat spikes is an effective mitigating strategy, but it requires a lot of water in a short time, which is often impossible to achieve.

 

Project Layout

A trial was conducted in the National University of Cuyo Faculty of Agricultural Science experimental vineyard in Mendoza, Argentina, on Malbec, Syrah and Bonarda grape varieties during the 2023 growing season from veraison to harvest. Treatment consisted of overhead pulsed water spraying only during heatwave days where minimum and maximum temperatures exceeded 21 and 35 degrees Celsius, respectively. 15-minute pulses of one minute on and two minutes off were given every hour from 08:00 to 20:00. Measurements were taken weekly and at several time points of the day. Measurements included:

  • Leaf and Stem Water Potential (LWP, SWP),
  • Stomatal Conductance (gs),
  • Leaf Temperature (LT),
  • Berry Temperature (BT),
  • Chlorophyll Content (CC),
  • Fluorescence (Fv/Fm) and
  • Performance Index (PI).

Berries were also collected on the sample dates and berry weight; soluble solid content and pH were measured.

 

Results

  • Two periods that qualified as heatwaves occurred during ripening. Interesting observations were made following the second, longer heatwave.
  • In the treated vines, LWP, SWP, Fv/Fm, PI, and gs were higher than the control vines, and LT was lower than the control vines.
  • One week after the second, longer heatwave, SWP, LWP and gs remained higher in treated vines.
  • At harvest, the bunch weight was significantly higher in treated vines than control vines in all cultivars, but no difference was recorded in anthocyanin concentration.

 

Significance of the study

The cooling treatment proposed in this trial used significantly less water per vine than conventional irrigations before and during heat waves, lowering the physiological stress on the vines and maintaining production and quality. This method can be a valuable tool to mitigate the adverse effects of heat waves during dry seasons when irrigation water is restricted.

 

Reference
Wilson, A. et al. (2024). Overhead spray water treatment as a mitigation strategy to alleviate vine stress and safeguard grape quality during heatwaves. OENO One58(2). https://doi.org/10.20870/oeno-one.2024.58.2.7847

 

Image: Shutterstock

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