Changes in morpho-physiological traits and phytochemical composition of Cannabis sativa L. treated with microbial biostimulants across different substrates

Cannabis is a versatile crop with multiple uses, making its production highly significant. Its growth is influenced by various factors, including growing medium. Beneficial microbes, as a sustainable approach, can impact plant growth, but their effects on cannabis' chemical profile are not well understood. This study examined two substrates (pure coco fibre and potting soil containing Sphagnum peat moss and perlite) and a microbial biostimulant comprising five Bacillus strains (two B. velezensis, two B. megaterium, and one B. licheniformis) on cannabis growth and secondary metabolites across all growth stages. The results show that biostimulant inoculation increased flower yield by 16 % in coco fiber and 12 % in potting soil compared to uninoculated controls. It also enhanced CBDA (cannabidiolic acid) and THCA (tetrahydrocannabinolic acid) concentrations by 5 % and 10 % in coco fibre and potting soil, respectively. Biostimulant-treated plants showed a 5 % increase in total terpene levels in coco fibre but not in potting soil. Regarding growing medium, cannabis grown in potting soil showed greater overall biomass accumulation (leaf, stem, and flower) and higher leaf chlorophyll concentrations during both vegetative and reproductive stages. In contrast, coco fiber promoted root growth during the vegetative stage and resulted in significantly higher cannabinoid and terpene concentrations at maturity. Hence, coco fibre may be advantageous for enhancing cannabinoid and terpenoid profiles, while potting soil is better suited for maximizing plant yield, depending on the desired production goals. These findings emphasize the critical influence of substrate type and biostimulant application, and their interaction, in optimizing cannabis cultivation practices.