Does water deficit negatively impact wine grape yield over the long term? Original language of the article: English.
Like many other woody perennial crops, grapevine reproductive development occurs over a two-year cycle. Given that water deficits are commonplace in viticulture, especially for red wine grape production, this raises questions about how water deficit in the current season could potentially impact yields the following year. This article will focus on the long-term effects of water deficits on grapevine yield.
Grapevine yield formation
Grapevine yield is the product of individual berry size and the total number of berries per vine. Each of these two yield components are themselves made up of different components. The total number of berries per vine is the product of the number of clusters per vine and the number of berries per cluster. The latter is itself a product of flowers per cluster (inflorescence) and percent berry set. Accordingly, water deficit can negatively affect yield via reductions of any of these components.
The effects of water deficits in the current season
Current season water deficits slow vegetative growth, ultimately limiting photosynthesis and canopy development. These impacts are more pronounced if the water deficit occurs preveraison, particularly around bloom, when shoot growth rates are at their maximum. At the onset of mild water deficit, vines reallocate energy (i.e. carbohydrates) from supporting shoot growth to supporting root growth, presumably to extract more soil water. Photosynthesis is reduced due to a smaller canopy with less leaf surface area.
If the water deficit continues and intensifies, leaves reduce water loss by closing stomata and changing their leaf orientation to the sun. These responses reduce photosynthesis at the leaf level by limiting gas exchange and reducing light interception. Less sugar production means less sugar export to sinks such as berries, root tips, and also developing buds and storage reserves. Thus, negative impacts on vegetative growth and development in the current season will negatively affect whole-vine carbohydrate production that ultimately supports perennial productivity and survival.
Current season water deficits can reduce yield through several yield components (Fig. 1). Both pre- and postveraison water deficits reduce berry size. Even when preveraison water deficits are released at veraison – as is often the case in many regulated deficit irrigation strategies – they have lasting effects on growth such that berry size will not “catch up” if vines are well-watered postveraison
Figure 1. The timing of water deficits dictates the exact effect on yield in the current and following season.

Seasonal dynamics of carbohydrate reserve storage
Woody perennials store energy in permanent structures (e.g. woody roots, trunk, cordons, etc.) to survive winter and support vegetative growth prior to the development of mature leaves
Water deficit effects on bud fruitfulness and long-term productivity
Bud fruitfulness is determined the year prior to harvest when inflorescence primordia are initiated in the developing buds (Fig. 2). This process begins just after flowering and is completed by veraison
Figure 2. Bud fertility is determined the year prior to harvest when inflorescence primordia are initiated in the developing buds. Adapted from Matthews M. (2016)

Recently, a long-term study of 15 red wine grape cultivars grown in a spur-pruned system evaluated reproductive development over five years. Cultivars were subjected to yearly pre- and postveraison water deficits, and results showed that only preveraison water deficits negatively impacted bud fruitfulness, with very few differences among cultivars
In the final year of the study, all vines were kept well-watered to observe true carryover effects on yield. Yields recovered somewhat due to increased berry size, but clusters per vine (and yield) remained low in vines that had previously experienced preveraison water deficits. While this confirmed the negative carryover effects of preveraison water deficits, clusters per vine never fell below a minimum value. This shows that despite severe preveraison water deficits over the long term, vines remained somewhat productive and continued to initiate clusters in buds. Presumably, previously accumulated carbohydrate reserves were being remobilized to support this minimum level of production, but it is unclear to what degree this minimum level of productivity would have remained, and for how long into the future. This implies that younger vines – carrying less stored carbohydrate reserves – may be more susceptible to production loses across multiple seasons. With respect to preveraison water deficits, specific practices and impacts can be considered in two phenological stages (Fig. 3).
Figure 3. When managing preveraison water deficits specific practices are advised depending on the phenological stage.

Conclusions
In viticulture, water deficits can vary in their intensity, timing, and duration. All of these factors will affect the exact impact that the deficit has on fruit yield. However, it is clear from the literature that severe preveraison water deficits will reduce berry size in the current season, and clusters per vine in subsequent seasons
The translation of this article into English was offered to you by Moët Hennessy.
NOTES
- Ojeda, H., A. Deloire, and A. Carbonneau, Influence of water deficits on grape berry growth. Vitis, 2001. 40(3): p. 141-145.
- Guilpart, N., A. Metay, and C. Gary, Grapevine bud fertility and number of berries per bunch are determined by water and nitrogen stress around flowering in the previous year. European Journal of Agronomy, 2014. 54: p. 9-20.
- Tixier A, Gambetta GA, Godfrey J, Orozco J and Zwieniecki MA (2019) Non-structural Carbohydrates in Dormant Woody Perennials; The Tale of Winter Survival and Spring Arrival. Front. For. Glob. Change 2:18. doi: 10.3389/ffgc.2019.00018
- Rossouw, G. C, Smith, J. P, Barril, C., Deloire, A., & Holzapfel, B. P. (2017). Carbohydrate distribution during berry ripening of potted grapevines: Impact of water availability and leaf-to-fruit ratio. Scientia horticulturae, 216, 215-225. doi: 10.1016/j.scienta.2017.01.008
- Williams, L.E., Bud Development and Fruitfulness of Grapevines, in Raisin Production Manual, L.P. Christensen, Editor. 2000, University of California. p. 24-29.
- MATTHEWS M., 2016. Terroir and other myths of winegrowing. Univ of California Press.
- Levin, A.D., M.A. Matthews, and L.E. Williams, Effect of Preveraison Water Deficits on the Yield Components of 15 Winegrape Cultivars. American Journal of Enology and Viticulture, 2020. 71(3): p. 208-221.
- Carbonneau A., Torregrosa L., Deloire A., Pellegrino A., Pantin F., Romieu C., Ojeda H., Jaillard B., Métay A., Abbal P., 2020. Traité de la Vigne, Physiologie-Terroir-Culture, Dunod Editeur, Paris, France, ISBN 978-2-10-079857-5, 689 p.
References
- Ojeda, H., A. Deloire, and A. Carbonneau, Influence of water deficits on grape berry growth. Vitis, 2001. 40(3): p. 141-145.
- Guilpart, N., A. Metay, and C. Gary, Grapevine bud fertility and number of berries per bunch are determined by water and nitrogen stress around flowering in the previous year. European Journal of Agronomy, 2014. 54: p. 9-20.
- Tixier A, Gambetta GA, Godfrey J, Orozco J and Zwieniecki MA (2019) Non-structural Carbohydrates in Dormant Woody Perennials; The Tale of Winter Survival and Spring Arrival. Front. For. Glob. Change 2:18. doi: 10.3389/ffgc.2019.00018
- Rossouw, G. C, Smith, J. P, Barril, C., Deloire, A., & Holzapfel, B. P. (2017). Carbohydrate distribution during berry ripening of potted grapevines: Impact of water availability and leaf-to-fruit ratio. Scientia horticulturae, 216, 215-225. doi: 10.1016/j.scienta.2017.01.008
- Williams, L.E., Bud Development and Fruitfulness of Grapevines, in Raisin Production Manual, L.P. Christensen, Editor. 2000, University of California. p. 24-29.
- Matthews M., 2016. Terroir and other myths of winegrowing. Univ of California Press.
- Levin, A.D., M.A. Matthews, and L.E. Williams, Effect of Preveraison Water Deficits on the Yield Components of 15 Winegrape Cultivars. American Journal of Enology and Viticulture, 2020. 71(3): p. 208-221.
- Carbonneau A., Torregrosa L., Deloire A., Pellegrino A., Pantin F., Romieu C., Ojeda H., Jaillard B., Métay A., Abbal P., 2020. Traité de la Vigne, Physiologie-Terroir-Culture, Dunod Editeur, Paris, France, ISBN 978-2-10-079857-5, 689 p.
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