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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Summer brings new challenges for vineyards, with the appearance of various pathogens. While downy mildew is a concern in spring due to frequent rainfall, summer sees the prevalence of other harmful diseases that can impact on grape quality.

What diseases commonly affect vines in summer?

Oidium and Black Rot are two pathogens that can seriously affect leaves and bunches during growth and veraison. Powdery mildew, in particular, does not require rain or leaf wetness to develop, making it a threat even in summer, which is generally a less rainy period.Black Rot, on the other hand, poses the greatest threat to vines during the critical phenological phase between the fall of the flower caps and veraison.

Post-veraison, grey rot, or botrytis, is particularly problematic. This fungus feeds on the sugars contained in the berries, damaging the bunches and encouraging the development of acid rot. It also imparts unpleasant odours and flavours to the wines produced.

Major consequences for vineyard health and wine quality

The impact of these diseases on vineyard health can be devastating, reducing both yield and quality of the harvest. Grapes affected by these pathogens often lead to wines with undesirable aromas and tastes, far from the desired quality level.

Prevention : an effective strategy

Proactive control and prevention strategies are essential to protect vineyards from these summer diseases.

Vineyard maintenance for optimum management

It is important to select resistant grape varieties and prune properly to improve air circulation and reduce humidity, which limits the development of pathogens. Frequent inspection of the vines allows early detection of the first signs of disease. It is crucial to intervene immediately when symptoms appear to prevent the spread of disease.
The application of specific fungicides and biocontrol products, such as plant extracts or antagonistic micro-organisms, must be carried out in accordance with recommended treatment schedules or the predictions of disease DSTs (Decision Support Tools).
In the case of a plot sensitive to black rot, it is useful to use anti-mildew or anti-oidium products that also have an anti-black rot action to have a comprehensive defense strategy.

Vigilance for high-performance vineyards

Even in the drier summer months, we must not lower our guard. Vigilance and early intervention are crucial to maintaining healthy vineyards and guaranteeing high-quality wine production. Decision support systems (DSS), such as Vintel®, provide precise alerts on disease pressures. This enables winegrowers to optimise treatment timings and implement effective preventive measures, thereby enhancing vine protection and securing the future harvest against summer diseases.

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Understanding heat waves

With climate change, prolonged heat waves are becoming more frequent and intense. It is vital for winegrowers to understand the extent of these phenomena so that they can adapt their practices and protect their vineyards.   

Heat waves are periods with temperatures above 35-35°C that persist for several days. They can cause heat and water stress, affecting vine growth and grape quality.

However, it’s not just the temperature that defines a heat wave; the vapor pressure deficit (VPD) also plays a crucial role. VPD measures the difference between the amount of moisture in the air and the maximum amount the air can hold at a given temperature. A high VPD means the air is very dry, which increases the evaporation of water from the vine leaves. This leads to more intense water stress, as the vines lose water faster than they can absorb it.

These conditions of high heat and low humidity can cause both thermal and water stress, affecting vine growth and grape quality.

Identifying the risks for vineyards

Heat waves do not affect all vineyards in the same way. Different factors, such as geographical location, soil type and the age of the vines, influence the vulnerability of vineyards to these extreme conditions.

Vineyards in the Mediterranean or in arid regions are at greater risk.

Soils poor in organic matter, such as light and sandy soils can weaken plants. Young or poorly rooted vines are also more  vulnerable.

What impact do high temperatures on vines?

High temperatures can have a variety of, often negative, effects on vines. It is crucial to understand these impacts to adopt effective management strategies.

High temperatures contribute to stomatal closure, reducing photosynthesis and metabolic processes. Another impact is the acceleration of ripening, which can lead to over-ripening of the grapes. Finally, high temperatures can lead to undesirable changes in the chemical composition of the grapes, altering the sugar/acid balance and, ultimately, the taste of your wine. These effects are mainly due to the breakdown of organic acids and an increase in sugar levels, resulting in wines that lack ‘freshness’ and have higher alcohol contents.

In fact, high temperatures accelerate respiration and gluconeogenesis, processes that consume the malic acid accumulated during fruit ripening. Heat waves can also impact wine aromas. These are derived from various volatile compounds that are influenced by the growing conditions of the grapes. Heat can alter the concentration and profile of these aromatic compounds, affecting the bouquet and complexity of the final wine. Anthocyanines are also negatively affected by high temperatures, resulting in lighter colouring red wines.

Heat damage

Beyond direct heat stress, hot weather can cause various types of damages in vineyards. Proactive management is to minimising these risks.

Grape berries exposed to direct sunlight can suffer significant damage. High temperatures can cause sunburn, which manifests itself as brown and necrotic spots on the berries and results in dried up berries and leaves. This damage can not only reduce the quality of the fruit but also increase its susceptibility to infection and disease. 

Water stress is another crucial factor linked to high temperatures. When exposed to these conditions, vines need more water to maintain their physiological functions. Without adequate irrigation, this can lead to excessive water stress. Lack of water can reduce photosynthesis, slow growth and decrease sugar production in the berries.

Heat stress can also disrupt the absorption of nutrients by the vines. For example, the absorption of nitrogen, an essential element for plant growth and development, can be significantly reduced as a result of heat stress, especially when the soil is dry. This nutritional deficiency can weaken vines, making them more vulnerable to disease and reducing their ability to produce high-quality grapes.

What strategies can be used to protect vineyards from heat peaks ?

Fortunately, there are several strategies you can implement to protect your vineyard from the effects of heat waves. Adopting appropriate practices can help to maintain the health of the vines and the quality of production.


Embrace technology

Modern technology can be a huge help in managing your vineyard during heat waves. Decision Support Tools like Vintel® provide alerts and irrigation advice tailored to heat events, helping you stay proactive.

By understanding and applying these strategies, winegrowers can better protect their vineyards from the harmful effects of heat waves and maintain the quality of their production.

For more information, please contact us: Vintel® » Contact us | Vintel® (vintel-itk.com)

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This year 2024, French vineyards are experiencing an unprecedented level of powdery mildew pressure. Vines were hit by early contaminations starting in late March, owing to early phenology and mild, wet weather. Such an early onset of attack is exceptional in this regionWeather conditions in April and May, marked by heavy rainfall, exacerbated the situation, making disease management particularly difficult. While some regions are beginning to benefit from drier weather, allowing better control of the disease, the importance of vigilance and effective application of treatments remains crucial to limit damages.

Downy mildew, a significant impact on plants and yields

Downy mildew, caused by the pathogen Plasmopara viticola, attacks various parts of the vine: leaves, bunches and berries. This disease has several negative effects:

It reduces the leaf surface used for photosynthesis. Affected leaves exhibit oily yellow spots on their upper surface and white mold on their underside.

It damages the berries turning them brown and crushed, consequently decreasing the quality and yield of the harvest.

It weakens the shoots, preventing shoot development and wood formation, making winter pruning more difficult. These combined effects reduce the vine’s reserves, compromise berry growth and make the plants more vulnerable.

What conditions are conducive to risk?

The development of downy mildew is favoured by specific climatic conditions:

Ideal temperatures for the spread of the disease are between 20 and 25°C with a humidity level of 85% or more.
Prolonged rainfall, dew and morning fog exacerbate the risk of contamination.
Periods of vigorous vine growth, when new shoots are most vulnerable, are particularly critical. In addition, certain grape varieties, such as Cabernet Franc, Cabernet Sauvignon, Chardonnay and Merlot, are particularly sensitive to mildew.

Appropriate treatment and prevention methods

Copper-based fungicides and specific systemic products are commonly used to combat downy mildew. It is essential to alternate the types of fungicide used to prevent the pathogen from developing resistance. In addition, combining substances with different modes of action and creating spatial heterogeneity in their application helps to prevent the development of pathogen resistance.

Various cultivation techniques can prevent downy mildew, such as pruning to improve air circulation around the plants, removing infected debris to reduce sources of contamination, and ensuring effective drainage to avoid puddle formation. Green pruning eliminates unnecessary shoots and promotes shoot aeration; maintaining a cover crop protects the soil and reduces water or contaminated soil splashes. Trellising and leaf removal also improve aeration. Finally, controlling plant vigour by limiting fertilization prevents excessive growth, which is conducive to powdery mildew.

Protecting vines effictively

For an effective protection against downy mildew, it is essential to follow reliable weather forecasts when planning treatments, to avoid water stagnation around the plants, and, in years with high disease pressure, to ensure a continuous phytosanitary protection without excessively long intervals between treatments. It is also important to regularly check the functionality and efficiency of sprayers, and to use decision-support systems such as Vintel to receive risk alerts on downy mildew and other diseases

Proactive, well-informed management is key to effective powdery mildew control. By combining different strategies, winegrowers can protect their vines and ensure the quality of their harvest inspite of the challenges posed by the unfavourable climate conditions of 2024.