Vine physiological parameters, such as yield per square meter, pruning weight per meter of shoot, and leaf nitrogen content (N-tester readings) did not show significant differences between biodynamically treated and control vines (Figure 1). This aligns with previous research, indicating that biodynamic preparations have minimal impact on vine vegetative growth ¹ . The absence of yield differences corroborates findings from studies on various grape varieties, including Merlot, Sangiovese, Cabernet Sauvignon, and Riesling ² .

Net photosynthesis exhibited a significant difference at only one measurement point (8 May 2018; Figure 1D). This isolated finding suggests that the biodynamic preparations may have had a transient effect on photosynthetic activity, though it was not consistent across other measurement periods. This result is consistent with other long-term studies on Riesling, which also reported negligible differences in photosynthetic rates between biodynamic and organic treatments ³ .

Berry quality parameters, including sugar concentration, individual berry weight, and organic acid concentrations (malic and tartaric acids), did not differ significantly between the treatments. This is consistent with most published studies, which generally report no significant differences in sugar concentrations between biodynamic and organic management ⁴ .

Figure 1. Yield and vine physiology. A) Yield per square meter, B) Pruning weight per metre of shoot as a proxy for vigour, C) N-tester, and D) net photosynthesis. Blue bars: blocks treated with water (without biodynamic preparations); orange bars: blocks treated with biodynamic preparations 500 and 501. * indicates significant differences between treated and non-treated blocks in the respective year.

The results of the carbon-13 discrimination analysis of sugars in berries from 2017 and 2018 suggest that the vines did not experience water deficit during berry ripening, regardless of treatment ⁵ . This contrasts with other studies that observed lower pre-dawn water potentials in biodynamic plots ⁶ , which might be attributed to methodological differences or site-specific conditions.

The analysis of soil physical properties, including bulk density, water holding capacity, structural stability, and macropore volume, revealed no significant differences between the biodynamic and control treatments over the study period (2017-2020; Figure 2). These findings are in line with previous research indicating minimal impact of biodynamic preparations on soil physical properties ⁷ .

Figure 2. Soil physical properties. A) Soil bulk density, B) Water-holding capacity at -60 hPa, C) Soil structural stability, assessed by Mean Weight Diameter, and D) Macropores volume at -60 hPa. Orange bars: plots treated with biodynamic preparations 500 and 501; blue bars: plots treated without biodynamic preparations. * Indicates outliers.

DNA sequencing of soil fungal communities showed no significant differences in fungal diversity or community composition between plots treated with biodynamic preparations versus water (Figure 3). This supports findings from Hendgen et al. (2018) ⁸ , who also reported negligible short-term effects of biodynamic preparations on microbial communities.

Figure 3. Non-metric multidimensional scaling (NMDS) plot showing differences in fungal composition across soil samples. This ordination indicates no significant differences in fungal communities between samples treated with biodynamic preparations (red dots) and water (blue dots). Dots (i.e. fungal communities) that are closer to one another are more similar than those further apart.

Our findings align with a broad body of literature, suggesting that biodynamic viticulture does not confer significant advantages or disadvantages over organic viticulture in terms of vine and berry physiology, soil physical properties, or soil microbiome composition (reviewed by Döring et al., 2019 ⁹ ). However, some studies have noted minor differences in sensory properties and yield under specific conditions ¹⁰ .

The lack of consistent and significant benefits of biodynamic preparations in our study raises questions about the added value of these practices, especially considering the higher production costs associated with biodynamic farming, which are 10 to 15 % higher than in organic production ¹¹ . While biodynamic farming is promoted for its potential environmental benefits and improved crop quality, our results suggest that these claims require further substantiation through controlled, long-term (6 years) studies in which different measurement parameters are included.