Vineyard irrigation is a necessary part of vineyard management in dry wine growing regions where winegrowers completely or partly rely on irrigation water. With irrigation, winegrowers can control vine growth and grape quantity and quality. This is because water availability is a crucial factor affecting plant physiology and the quality of grapes. In dry production areas such as the Mediterranean region, the use of irrigation is thus a fundamental practice which grants the economic sustainability of viticulture.
Vineyard irrigation and climate change
In addition to areas traditionally considered as “dry” during the growing season, new regions are increasingly showing the need of irrigation. The climate change underway is leading to an increase in temperatures and a reduction in rainfall in the summer period, increasing water stress in vineyards, which could potentially undermine both yield and grape quality. These changes will make it necessary to implement irrigation in viticultural areas for which drought is a new phenomenon. The increase in temperatures will also cause a reduction in the water resources available, making it necessary to decrease the water footprint by using deficit irrigation strategies which optimize water use efficiency.
Such practices are already routinely adopted in viticultural areas with limited rainfall throughout the production season. Indeed, irrigating with small amounts of water has the effect of reducing growth and canopy size, limiting transpiration losses and therefore maintaining production and quality at reduced water inputs. However, particular care must be exerted, as the line between moderate and excessive water stress is very thin and crossing it might lead to incomplete/unbalanced ripening and deteriorate the polyphenolic and aromatic profile of wines. For this reason, a deficit irrigation strategy needs to be carefully planned and its effects need to be continuously monitored.
What is deficit irrigation in viticulture
Deficit irrigation maximizes the efficiency of water use, by concentrating limited seasonal water supplies to drought-sensitive crop growth stages. Outside these periods, irrigation is limited or even unnecessary if rainfall provides a minimum supply of water. Water application is therefore inferior to the actual water needed for maximum growth. While this inevitably results in plant drought stress and some production loss, it maximizes productivity for a given amount of water and stabilizes yields.
For grapevine, the effect of water deficit on fruit growth varies according to the period during which it is applied. Research shows that it is greater when it is applied during berry formation (between flowering and veraison) when can limit cell division and expansion and decrease the final size of berries and total yield. Similarly, a stress applied at the time of flower bud differentiation can negatively impact fruitfulness and production the following year.
Fruit quality is also sensitive to water stress, depending on its levels. Whereas moderate stress can increase sugar concentration and anthocyanins and phenol compounds in berries (thereby enhancing wine color and aroma), excessive stress and high temperatures could cause a photosynthetic limitation reducing the accumulation of sugar. Finally, water stress can impact on acid content in grapes in interaction with temperature. This effect is particularly pronounced after veraison, when rapid acid degradation due to high temperatures and water stress can result in dull wines lacking freshness and crispness.
Using Vintel for deficit irrigation: an experimental study during the Italian drought of 2022
It is now clear that under climate change, the key to viticultural sustainability will be the adoption of smarter and more precise water management strategies. For that, it is crucial to have a complete vision of the water status of vineyards and its evolution over the production season. New technologies provide us with different tools that can support informed irrigation choices, and optimize water use during drought. One of these tools is the irrigation DSS Vintel, which uses accurate plant-soil models to simulate vineyard water status, and give irrigation recommendations, day by day according to production objectives.
A recent study by the university of Udine, Italy, has highlighted that Vintel can indeed help plan and optimize irrigation to preserve production and quality in areas hit by summer drought, which is becoming more and more frequent. Vintel has been chosen by the University of Udine within the European project “Aquavitis” as a tool to conduct trials on the effects of water availability and the impacts of climate change on the vineyards of the Friuli Venezia Giulia region, in North-Eastern Italy.
Indeed, in the spring-summer of 2022 Northern Italy has experienced one of the worst droughts in the last 70 years, with precipitations reaching a historical minimum and rivers running almost dry. The drought has resulted in water restrictions and has hit hard the agricultural sector, as low river levels made irrigation difficult.
Paolo Sivilotti, the researcher who supervised the trials explains : ” The test was conducted in 2021 and 2022 near Udine. It analysed the response of Pinot gris, a typical variety from the region, to three different water treatments: no stress, moderately stressed, severely stressed. ” To monitor and maintain these water stress levels over the season, Mr. Sivilotti used Vintel, which simulates predawn water potential as an indicator of plant water status.
Using Vintel, water potential was mantained at:
- No stress : -0.2 MPa over the whole season
- Moderate stress : -0.35 MPa between flowering and harvest
- Severe stress : -055 MPa between flowering and harvest
” What was really interesting was to see whether a deficit irrigation strategy could help optimize water use and what level of stress should be maintained after flowering to ensure a satisfactory yield and grape quality. The DSS Vintel was the ideal tool to conduct this study because its models do not just simulate soil moisture but provide a direct estimate of the effect that soil water shortage has on vine water status. The pressure chamber measures made during the growing seasons confirmed the accuracy of simulations, making any DSS adjustment unnecessary.”
The results show that “the moderately stressed regime allows to save 31% of irrigation water (35 mm) with modest impacts on yield and physiology, and without any repercussions on quality“. Indeed, a wine tasting panel has tried the wines produced in 2022, and no difference between the stressed and non-stressed wines has been remarked.
“Obviously more studies are needed to assess the best deficit irrigation strategies in different viticultural contexts.”
However, results confirm that under climate change, precision deficit irrigation can be a valuable strategy preserving production, quality and decreasing the water footprint of viticulture.
“Not only, during extreme events like the one that hit Northern Italy this summer, deficit irrigation might be the only possible alternative, if water restrictions are put in place or if water becomes too expensive.” In this context, tools like Vintel are precious allies to vine growers in the creation a climate resilient, more sustainable viticulture.
If you want to know more about Vintel, see here !
Agronomist and scientific editor