Impact of biodynamic preparations on soil properties suggests enhanced microbial community diversity in vineyards in Bordeaux, France

A six-year field study was conducted at Château Lafite Rothschild in Bordeaux, France, to investigate the effects of biodynamic (BD) preparations on soil microbiological and chemical properties. Basal respiration (B-Resp), microbial biomass carbon (MBC), total carbon (C-total), and soil organic carbon (SOC) were analyzed in soils from organically managed vineyards, comparing those without (BD −) and with BD preparations (BD +). Accordingly, two treatments were arranged in a randomized block design with four replicates. Soil microbial activity was assessed using the multi-substrate-induced respiration (multi-SIR) method, which measured the catabolic response to 17 low molecular weight organic substances (LMWOS). The results indicated that BD + plots exhibited significantly higher B-Resp (+ 40.0%) and MBC (+ 33.7%) compared to BD − plots, suggesting enhanced microbial metabolic activity. An upward trend in SOC (+ 17.4%) and C-total (+ 16.7%) was observed in BD + soils, indicating improved carbon sequestration potential. The multi-SIR analysis revealed a significant increase in respiratory responses to D-glucose and D-fructose in BD + plots, and an increasing trend of respiratory response for 13 other LMWOS. A higher respiratory response suggests a lower anabolic demand for specific substrates. Principal component analysis distinctively separated BD + from BD − treatments, underscoring the microbial functional profile changed by BD preparations. The significant increases observed in BD + treatments, particularly in B-Resp, MBC, and the catabolic use of D-glucose and D-fructose, demonstrate that integrating BD preparations into organic vineyard systems enhances the biological activity of microbial communities in soils. In the ongoing experiment further research will allow us to understand better longer-term impacts of BD on soil properties.