Combining soil management and nitrogen fertilisation to optimize vine nutrition in Swiss vineyards

Abstract

In the pursuit of more sustainable viticulture, many winegrowers have drastically reduced nitrogen (N) fertilisation and abandoned chemical weed control in favour of permanent grass cover. While these practices benefit soil health and biodiversity, they often increase competition for water and nutrients. After several years, such competition can lead to vine stress, characterized by reduced vigour, lower yields, and a decline in wine quality. White grape varieties are particularly sensitive to N deficiency, resulting in wines with fewer varietal aromas and increased bitterness or astringency (Bell and Henschke, 2005; Verdenal et al., 2021). Although winery N additions help to maintain fermentation kinetics, they do not produce wine with similar sensory characteristics (Tian et al., 2022).

To address these challenges, Agroscope launched the “Azote Vaud” project (2024–2026) with the financial support of the canton of Vaud and the Bovard Foundation. The project aims to evaluate the combined effects of soil management and N fertilisation on vine N status, yield, and wine composition. A network of eight experimental plots was established in the canton of Vaud, Switzerland, planted with Vitis vinifera Chasselas and with a common split-plot design. The treatments compare full grass cover versus a weeded vine row, and localized soil N fertilisation (50 kg N/ha) versus no fertilisation. In 2025, three out of eight plots were vinified to investigate the relationship between the two combined factors and the composition and sensory properties of the wines.

Preliminary results reveal substantial differences in the yeast assimilable N (YAN) content of musts across the network, with most plots falling below the critical deficiency threshold (<140 mg N/L). Simple weed removal under the vine row significantly increased YAN concentration by an average of +28 mg N/L compared to fully grassed plots. The combination of weed control and localized N application successfully restored YAN levels above the deficiency threshold, confirming the strong influence of soil management on vine N nutrition and the complementary role of fertilisation. The 2025 winemaking is currently underway, and a synthesis of the results from 2024 and 2025 will be presented.

The project will continue through 2026, with further analyses focusing on soil composition, vine recovery and wine composition. These results will provide practical guidance for balancing sustainability goals with the nutritional requirements of the vine, ensuring both environmental and oenological quality in Swiss viticulture.

References

Bell, S.-J., & Henschke, P. A. (2005). Implications of nitrogen nutrition for grapes, fermentation and wine. Australian Journal of Grape and Wine Research, 11, 242-295. https://doi.org/10.1111/j.1755-0238.2005.tb00028.x

Tian, T., Ruppel, M., Osborne, J., Tomasino, E., & Schreiner, R. P. (2022). Fertilize or supplement: the impact of nitrogen on vine productivity and wine sensory properties in Chardonnay. American Journal of Enology and Viticulture, 73(3), 148-161. https://doi.org/10.5344/ajev.2022.21044

Verdenal, T., Dienes-Nagy, Á., Spangenberg, J. E., Zufferey, V., Spring, J.-L., Viret, O., Marin-Carbonne, J., & van Leeuwen, C. (2021). Understanding and managing nitrogen nutrition in grapevine: a review. Oeno One, 55(1), 1-43. https://doi.org/10.20870/oeno-one.2021.55.1.3866