Effect of weather conditions on yield components

by | Jun 30, 2020 | South Africa Wine Scan

Aim of the study

In this project, researchers aimed to quantify the relationship between yield components and the climatic conditions at critical growth stages for wine grapes in a cool climate environment.

Project layout

  • This was a long-term field study on Sauvignon blanc in Marlborough, New Zealand.
  • Four different vineyards were established in 2004, both containing two-cane and four-cane trained VSP vines.
  • Phenology and yield (bunch number, berry mass) were monitored up to 2019 in some of the vineyards.
  • This data was combined with meteorological records and then a multi-variable mixed linear model was used to assess the relationship between various yield components and weather conditions.


  • The critical periods for each yield component and weather factor were optimised based on the maximum likelihood returned from the mixed linear model.
  • The results showed that temperatures during the pre-flowering (mainly before 50% flowering) period, significantly impacted all yield components.
  • This period in both the current season and the previous season (when inflorescence initiation occurred) has a critical impact on yields.
  • Pre-flowering conditions of the current season affected berry number per bunch, berry mass and bunch mass in the current season while it affected bunch number per vine in following season.
  • Maximum daily temperature had the biggest effect on bunch number (inflorescence initiation) and overall yield. It also greatly influenced berry number and bunch mass, alongside minimum temperatures.
  • Rainfall around the flowering period had a negative effect on berry mass and bunch mass, whereas post-flowering rainfall had a strong positive effect on these parameters and overall yield.
  • In this study, radiation had a moderate effect.
  • The statistical model explained 60 to 85 percent of the seasonal variations in bunch number, berry number, berry and bunch mass and yield per vine.

Significance of the study

Seasonal differences in weather conditions cause marked variation in grapevine yield. This study showed that incorporating the correlations between yield components and climatic conditions into plant models, is likely to improve yield prediction for grapevines.


Zhu J., Fraysse R., Trought M. C., Raw V., Yang L., Greven M., Martin D., & Agnew R. (2020). Quantifying the seasonal variations in grapevine yield components based on pre- and post-flowering weather conditions. OENO One54 (2). https://doi.org/10.20870/oeno-one.2020.54.2.2926

Image: Shutterstock

Want to know more about how grapevine flowers form? Click here for a good read about this topic.

Winetech funded local research about the impact of a changing climate on grapevine physiology. Follow the article series here.

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