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.
Contact us now and ask for a demo!
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 :
- Visualise the peaks of nitrogen consumption in their vineyard for the ongoing season.
- Know when plants are stressed and consuming their own nitrogen reserves so to avoid their depletion
- Compare different fertilization strategies to see what is their potential impact over plant nitrogen and soil stocks
- Select the best cover crop for your vineyard and optimize its management (type, planting date, removal date etc.)
- Analyze the use of nitrogen in your vineyard after harvest. Is there sufficient N for building adequate plant stocks?
- Maximize the effectiveness of N applications by considering present and future water availability in the soil
- Save money by applying just the right amount of fertilizer at the right moment.
- Preserve soil and environmental resources by avoiding excess N application and N leak into the environment
Contact us now and ask for a demo!