The nitrogen isotope ratio (δ¹⁵N): exploration of a very large dataset for a better understanding of this indicator in viticulture

Abstract

Isotopic analysis have been proven to be particularly useful within the wine industry, either for water stress characterization (with the δ¹³C) or for countering potential wine fraud (with the use of δ¹⁸O, δ¹³C and δ²H) (Santesteban et al., 2014). Surprisingly, very little attention has been addressed to the isotopic analyses of nitrogen using the δ¹⁵N with the notable exceptions of Santesteban et al., 2024 and Spangerberg et al., 2023; 2021 who have paved the way in the comprehension of this analysis.

For a better understanding of this measurement, a very large dataset (>1500 points) of δ¹⁵N, δ¹³C and total nitrogen was collected on grape musts at harvest over multiple wine regions and varieties of France in 2025. Results revealed that δ¹⁵N was positively correlated with water stress which was still in debate in the literature. δ¹⁵N was also shown not to be correlated with total nitrogen which confirm its role as a nitrogen source indicator rather than a nitrogen content indicator. A random forest approach was used to differentiate the effect of the wineries and of the varieties on the isotopic signature which showed that the winery effect was considerable in determining the isotopic signatures of the samples while very little varietal effect was observed.

δ¹⁵N was also collected on grapevines petioles and grapevines leaves in five different experimental vineyards at flowering and at veraison. Little variation of δ¹⁵N was observed on leaves over the season while strong variation of δ¹⁵N on petiole was found (either positively or negatively). The difference of δ¹⁵N between floraison and veraison is thought to be a good indicator of a potential nitrogen stress over the season with the increase of ¹⁵N-enriched nitrogen assimilation and/or an increase in the proline content.

Finally, in one vineyard experiment, δ¹⁵N was collected on leguminous and non-leguminous cover crops as well as on grapevine leaves. Despite a low number of data points, δ¹⁵N was found to be a potential efficient tool for assessing the nitrogen efficiency of a leguminous cover-crop.

References

Santesteban, L. G., Loidi, M., Urretavizcaya, I., Galar, M., Crespo-Martínez, S., Royo, J. B., & Miranda, C. (2024). Nitrogen isotope ratio (δ15N): a nearly unexplored indicator that provides useful information in viticulture. OENO One, 58(2). https://doi.org/10.20870/oeno-one.2024.58.2.7961

Santesteban, L. G., Miranda, C., Barbarin, I., & Royo, J. B. (2015). Application of the measurement of the natural abundance of stable isotopes in viticulture: A review. Australian Journal of Grape and Wine Research, 21(2), 157–167. https://doi.org/10.1111/ajgw.12124

Spangenberg, J. E., & Zufferey, V. (2023). Soil management affects carbon and nitrogen concentrations and stable isotope ratios in vine products. Science of The Total Environment, 873, 162410. https://doi.org/10.1016/j.scitotenv.2023.162410

Spangenberg, J. E., Schweizer, M., & Zufferey, V. (2021). Carbon and nitrogen stable isotope variations in leaves of two grapevine cultivars (Chasselas and Pinot noir): Implications for ecophysiological studies. Plant Physiology and Biochemistry, 163, 45–54. https://doi.org/10.1016/j.plaphy.2021.03.048