Distinct and Combined Applications of Biochar and Wood Distillate Modulate Functional Responses in Young Vitis vinifera L

Biochar (BC) and wood distillate (WD), from agri-waste biomass, are promising sustainable soil amendments. This study evaluates their single and combined effects on morpho-physiological, biochemical, and nutritional responses of young grapevine (Vitis vinifera L.) plants. Grapevines were grown for 45 days in pots filled with commercial growing medium treated with BC (20%, w/w), WD (0.5%, v/v), or their combination (BC + WD). Plant morpho-biometric traits, as well as chlorophyll, sugars, amino acids, proteins, phenols, and nutrient contents, were determined. Post-harvest, growing media were analyzed for chemical and thermal properties, elemental composition, and nutrient bioavailability. Wood distillate alone significantly reduced chlorophyll content, likely due to decreased molybdenum bioavailability, and lowered root uptake of molybdenum, copper, iron, calcium, magnesium, and sodium, potentially enhancing salt tolerance. Both WD and BC individually reduced leaf glucose content. Biochar alone also decreased chlorophyll, probably because of high potassium content causing nutrient imbalances and increased root sodium accumulation, while limiting sodium translocation to leaves. The combined BC + WD treatment restored chlorophyll and glucose to control levels, suggesting a synergistic interaction that alleviated single negative impacts. Wood distillate induced stress-related metabolic changes, increasing amino acids but limiting protein synthesis. In contrast, BC partially mitigated these stress effects by enhancing protein accumulation and reducing phenol content. Co-application of BC and WD has the potential to improve nutrient use efficiency in young grapevines. The treatment-specific effects observed in plant and the growing medium underscore the importance of tailoring BC- and WD-based amendments for achieving optimal agronomic benefits.