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:

” 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.”

No water stress

Moderate water stress

Severe water stress

The results show that “the moderately stressed regime allowed to save 31% and 50% of irrigation water in 2021 and 2022  with modest impacts on yield and physiology, and without any repercussions on quality“. Indeed, a wine tasting panel has tried the wines produced in 2021, 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.

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Wine quality depends on the effective management of alcoholic fermentation, which is a key process carried out by the yeast Saccharomyces cerevisiae in the musts. One of the key factors in successful fermentation is the availability of yeast-available nitrogen (YAN). If the musts lack sufficient YAN, fermentation can be delayed or stopped altogether, resulting in the formation of undesirable compounds that alter the wine’s aroma. To avoid these problems, an adequate level of YAN is crucial.

What is YAN ?

To convert grape sugars into alcohol efficiently, yeasts need sufficient quantities of assimilable nitrogen, mainly in the form of ammonium and amino acids… Among amino acids, some, such as proline, are not assimilable by yeast. This is because Saccharomyces cerevisiae, unlike other yeasts, lacks external proteases (enzymes that digest proteins) and therefore cannot hydrolyze peptides and proteins to extract amino acids. Therefore, YAN includes only ammonium ions (NH4+), free amino acids, and some peptides, which means that assimilable nitrogen can represent less than 50% of the total nitrogen.

Nitrogen requirements of yeast during fermentation

Scientific studies show that a YAN level above 180-200 mg/L is optimal for ensuring regular and complete fermentation. Lower levels can lead to incomplete fermentation, leaving residual sugars and producing wines of lower quality. According to the Institut Français de la Vigne et du Vin (IFV), the minimum YAN level in a should be at least 140 mg/L, including 50 mg/L in the form of ammonia, toto prevent fermentation from stalling.

Furthermore, YAN also influences the aromatic profile of the wine. The production of aromatic compounds, particularly esters, largely depends on the amount of assimilable nitrogen available to the yeast. Generally, the initial concentration of assimilable nitrogen in the must is directly related to the quantity of aromatic compounds produced during alcoholic fermentation

Nitrogen fertilisation to improve must quality

YAN level is therefore a key indicator for winegrowers seeking to optimise the quality of their musts. Proper nitrogen fertilisation increases the nitrogen content of the berries. For example, trials carried out by the IFV between 2005 and 2009 showed that urea-based foliar fertilisation can boost the nitrogen content of berries by 50% to 100%, depending on the dose applied.

If musts are low in nitrogen, adding YAN as a nutrient during fermentation is an option. However, this method can result in different aromatic profiles compared to wines from vineyards with adequate nitrogen fertilization.

For example, a recent study on Chardonnay revealed that, while adding nitrogen in the form of diammonium phosphate or organic nitrogen during fermentation can achieve fermentation kinetics similar to those from vineyard fertilization, they produce wines with less pronounced tropical fruit aromas.

In summary, while cellar additions of nitrogen are effective for completing fermentation, conducting a balanced fertilization in the vineyard is preferred as it enhances the aromatic characteristics of the wine.

Using decision-support tools to control nitrogen nutrition

Decision-aid tools such as Vintel® are particularly useful for improving nitrogen nutrition in vineyards and, consequently, the fermentation process. These tools enable winegrowers to forecast the nitrogen requirements of their vines based on environmental conditions (soil, weather, cover crops) and the specific characteristics of plants (phenological stage, growth, target yield). Thanks to this data, winegrowers can fine-tune their fertilisation practices, optimising nitrogen uptake and, ultimately, the quality of their musts, ensuring that they ferment evenly to produce quality wines.

In short, precise fertilisation adapted to each vineyard is essential for producing high quality grapes and ensuring optimal fermentation. Effective management of assimilable nitrogen helps to prevent fermentation issues and produce top wines.

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Nitrogen as fertilizer in the vineyard

Nitrogen (N) plays a major role in all grapevine physiological processes. It is considered as a macronutrient, as it is required in larger amounts than the other mineral nutrients. It controls plant vigor and its absorption by the roots is dependent on the availability of water. A nitrogen deficient grapevine will not grow well, forming short inter-nodes, chlorotic (yellow) leaves and will produce less fruits with a reduced grape N content and possible delayed maturation.

Whereas nitrogen must be available to grant an adequate growth and photosynthesis, in viticulture too much nitrogen is also detrimental. Excess vigor leads to an extended vegetative growth period and competition with grape ripening. In addition, denser canopies and higher N content in leaves can increase vulnerability to fungal diseases.

In addition to controlling vegetative vigor, nitrogen affects the composition of grapes and the activity of yeast during winemaking. Indeed, nitrogen is a key yeast nutrient needed to carry out a successful fermentation and its presence as part of complex N-compounds in musts can affect the aromatic quality of wine.

All these functions make it difficult to control and to manage nitrogen fertilization in the best way. Since 2021, Vintel Nitrogen module by ITK provides a monitoring and forecasting service that can be used on a large scale to make the best decisions concerning N fertilization in a quick and cost-effective way to attain production goals.

How do you know how much nitrogen is needed by your vineyard ?

Fertilization is a regular practice for vinegrowers, and one which demands a particular expertise to attain the optimal balance between vigor and grape composition.

This expertise is even more relevant in a world that is more and more concerned with soil and environmental preservation. Indeed, wine growers are becoming increasingly aware of the detrimental effects of excess nitrogen leaking into the environment, causing water pollution and eutrophication. For this reason, over the past decades, the application of N in vineyards has been reduced with the aim of adjusting vigor and yield while preserving the environment.

In the last decades cover cropping has made its come-back in many vineyards, after a long period in which it was abandoned, as it was considered harmful for production. Indeed, whereas using cover crops have several benefits, ranging from soil protection to the control of  yield, in vineyards with low vigor, there is a concern of excessive competition for N resources with vines. In these cases, N-fertilizer application needs to be tailored to suit grapevines needs while considering the type of cover crop and its practices.

All these factors need to be considered when creating the nitrogen (N) management plan, to make the best use of N fertilizers. To conceive such plans it is very helpful to monitor vine N status and have a global vision of all the elements affecting its balance in the vineyard. A decision support tool  (DST) like Vintel Nitrogen module can provide these data in real time so that nitrogen management becomes easy and effective.

Vintel Nitrogen module predicts nitrogen availability

The new service within the Vintel DST, Nitrogen module boosts growers insight into the nitrogen status of their vineyard, informing decision-making.

This powerful solution makes it possible to visualize nitrogen stress and measure the impacts of nitrogen inputs on vine growth during the production season.  And off-season it helps adjust nitrogen application so that vines maximise their reserves and can re-start growth adequately. Because Vintel Nitrogen module considers the soil-plant water balance, it allows to apply fertilizer in the right amount to avoid leaking or wash out.  Moreover, the system provides a long-term weather forecast ranging several months in the future, that can help planning N purchase and application in the long term.

A nitrogen expert for winery management by the side of growers

Vintel Nitrogen module calculates daily nitrogen demands and consumption by plants, depending on nitrogen soil stocks, fertilizer application, cover cropping and other vineyard practices, and weather. This is possible because at the heart of Vintel Nitrogen module there are agronomic models of soil water balance, nitrogen mineralization and nitrogen allocation whose output provides an instant picture of your vineyard N status. Soil nitrogen dynamics over time are displayed through easy-to-interpret detailed graphs. Long-term weather forecasts allow to simulate the in season evolution of vineyard nitrogen, for a better planning of N-fertilizer applications.

Vintel Nitrogen module : for each plot, you can visualize detailed graphs showing nitrogen demands by the plant (top), nitrogen and water availability in soil (middle) and weather (bottom)

Vintel is a complete tool for the management of nitrogen allowing growers to :

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