Irrigation strategy and timing of canopy interventions to improve wine quality with minimal crop loss

by | Mar 1, 2024 | South Africa Wine Scan

A field study was conducted in the hot climate of the San Joaquin Valley, where producers struggle to achieve optimal berry colour. Canopy manipulation by hand is a costly endeavour, forcing producers to turn toward mechanical leaf removal. The aim of the study was to investigate the interaction between mechanical leaf removal and irrigation management and its influence on grapevine physiology, yield, and colour.


Project Layout

  • A two-way factorial split-plot design containing five treatments in Cabernet Sauvignon was utilised.
  • The two irrigation treatments were regulated deficit irrigation (RDI) and sustained deficit irrigation (SDI).
  • RDI was 50% crop evapotranspiration (ETc) from fruit set to veraison and 80% ETcfrom veraison to harvest, whereas SDI was 80% ETc from fruit set to harvest.
  • The three mechanical leaf removal treatments were removal during bloom, removal during fruit set and no removal.



  • Leaf removal during bloom and fruit set increased berry anthocyanins (colour) by 19% and 13%, respectively, without affecting yield negatively.
  • RDI increased berry anthocyanins at harvest by 14% compared to SDI, but with a sacrifice of 15% yield.
  • SDI affected yield minimally compared to RDI.
  • SDI, combined with mechanical leaf removal during bloom, is proposed as a solution to achieve optimal berry colour with minimal crop loss.


Significance of the study

These results echo similar work in South Africa under the same climatic conditions and production cost constraints. More emphasis should be placed on canopy density and the effective application of irrigation water in some spheres of the South African wine industry. A lot can still be done to increase wine quality, and the resources and tools are available to all.


Shijian Zhuang, Qun Sun, Paolo Sabbatini, Karl Lund, Matthew Fidelibus. Mechanical fruit-zone leaf removal and deficit irrigation practices interact to affect the yield and fruit quality of Cabernet Sauvignon grown in a hot climate. American Journal of Enology & Viticulture.


Image: Shutterstock

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