Impact of organic mulches on grapevine health, growth and grape composition in nutrient-poor vineyard soils

Effective vineyard management is essential for maintaining grapevine cultivation in semi-arid regions impacted by climate change. Utilising organic mulches is a viable soil management practice that improves soil properties, such as moisture retention, erosion control and soil structure. However, the effect of organic mulches on plant development and grape composition remains unclear. The present study analysed the effects of three organic mulches and two conventional soil management practices on vine physiology, agronomy and grape composition over three years under semi-arid conditions in northern Spain. Three organic mulches (spent mushroom compost-SMC, straw-STR and grapevine pruning debris-GPD) were compared with two conventional soil management practices (herbicide-HERB and tillage-TILL) in nutrient-poor soil. Physical and chemical soil properties, grapevine physiological response, leaf nutrition, growth development, yield and grape composition were evaluated in the Tempranillo cultivar. The SMC mulch improved soil water content, leaf nitrogen concentrations and vegetative growth, resulting in higher yields without compromising grape composition. Conversely, STR mulch increased soil water content, reduced soil temperature, and improved plant water status and leaf gas exchange variables without affecting vine growth and yield. However, no significant differences in grape carbon isotopic discrimination (δ13C) were observed between soil management treatments. SMC’s nutrient-rich composition, fine granularity and low C/N ratio could thus promote short-term plant development in poor-nutrient soils, and STR and GPD organic mulches may offer long-term benefits for vine development. A strong correlation was obtained between reflectance values and vegetative growth, yield and leaf nutritional content, offering a non-destructive and rapid assessment method. Overall, organic mulches represent a viable soil management alternative that enhances plant development and yield without reducing grape composition. This research provides valuable insights for winegrowers interested in suitable viticultural practices and highlights the importance of analysing soil and mulch properties to select the most appropriate organic mulch.