Seaweed-derived biostimulants are a promising strategy for improving crop performance in sustainable agriculture. In this context, this study evaluated the effects of foliar application of Kappaphycus alvarezii extracts, obtained from two Brazilian regions (São Paulo: Kal-SP and Santa Catarina: Kal-SC), at different concentrations (1%, 3%, 5%, and 7%) on the growth, biochemical profile, essential oil yield, and rhizosphere microbiome of Ocimum basilicum under field conditions. Morphological analysis indicated that the 5% and 7% concentrations increased plant height, biomass, root development, and inflorescence production, with biomass gains of up to 51% and essential oil production increases of up to 142% compared to the control. Biochemical responses varied by extract origin, with Kal-SC promoting greater increases in photosynthetic pigments, antioxidant activity, and carbon-related metabolites, whereas Kal-SP induced only minor metabolic changes. The algal biostimulant modulated essential oil yield and composition, promoting treatment-dependent shifts in major terpenoid compounds. Microbiome analysis showed no significant changes in alpha diversity, but significant shifts in beta diversity and functional groups, such as Bacillaceae, indicating rhizosphere reorganization. Overall, the effectiveness of K. alvarezii-based biostimulants depends on concentration and biomass source, highlighting their potential as sustainable agricultural bioproducts and the importance of standardized extraction for consistent outcomes.
Nunes et al. (Thu,) studied this question.