Phosphorus-solubilizing bacteria and phosphorus-enriched biochar enhance growth, cannabinoid content, and essential oil yield in salt-stressed hemp (Cannabis sativa L.).

Soil salinity induces phosphorus (P) deficiency, limiting crop productivity, yet the combined use of phosphorus-solubilizing bacteria (PSB) and phosphorus-enriched biochar (P-biochar) under salinity remains unexplored. This study presents a novel integrated PSB+P-biochar approach to improve growth and secondary metabolite production in Cannabis sativa L. under salinity stress. A completely randomized design with three independent replicates (each replicate containing two pots) was employed. A factorial experiment was conducted with two factors: salinity at two levels (0 and 100 mM NaCl) and soil amendment at six levels (control, B. subtilis, P. putida, P-biochar, B. subtilis + P-biochar, and P. putida + P-biochar). Seeds were inoculated with PSB and P-biochar was mixed into soil at 2% (w/w). Salinity decreased plant biomass, chlorophyll (Chl), relative water content (RWC), essential oil (EO) yield, and cannabinoids, while increasing proline and malondialdehyde (MDA) compared to the control (no salinity). In plants exposed to salinity stress, P-biochar in combination with B. subtilis and P. putida respectively increased shoot weight (25% and 24%), root weight (28% and 38%), Chl (33% and 29%), RWC (16% and 15%), proline (17% and 19%), EO yield (49% and 37%), cannabidiol (13% and 12%), and tetrahydrocannabinol (16% and 14%), but lowered MDA (23% and 21%) compared to salinity-only treatment. The results are limited to greenhouse conditions and require field validation. Nonetheless, this combined strategy is recommended to enhance plant resilience and optimize pharmacologically active compound production in saline environments.