Long-term vineyard management systems shape soil moisture dynamics, nitrogen cycling, and grapevine root distribution

Organic and biodynamic viticulture are increasingly promoted as sustainable alternatives to integrated management, yet their long-term effects on belowground processes remain underexplored. Previous findings showed that organically and biodynamically managed vines initially exhibited reduced vigor and yield but converged with, or exceeded, integrated management under hot and dry conditions. This study aimed to elucidate the belowground mechanisms underlying this shift by examining how management shapes grapevine root traits and soil resource dynamics. Belowground processes were analyzed in the INBIODYN trial (Geisenheim, Germany; established in 2006) by monitoring (i) soil moisture dynamics to 1.6 m depth (2023–2025), (ii) mineral nitrogen across phenological stages (2010–2023), (iii) soil chemical and physical properties (2012–2024), and (iv) grapevine root traits from soil cores to 0.9 m depth sampled in inter-row and under-vine positions. Organic and biodynamic management increased mineral nitrogen availability during the growing season and promoted greater total and fine root length than integrated management, with the strongest root responses in upper inter-row soil layers. Early-season soil moisture was lower under organic and biodynamic management, indicating enhanced competition for water, but differences diminished later in the season. Organic and biodynamic management reconfigure the soil-vine continuum by introducing short-term competition while promoting denser surface root networks and sustained nitrogen availability, likely driven by legume-rich cover crop management. These belowground responses are consistent with the gradual convergence of vine performance observed in this long-term trial and provide a plausible mechanistic basis for the observed improved tolerance to hot and dry conditions.