Biochar-microbe synergy enhances auxin-mediated soil–plant interactions for canola productivity in alkaline calcareous soil

significantly enhanced plant biomass, stem diameter, and grain yield by up to 203%, 127%, and 212%, respectively, in Faisal canola compared to the control. Biochar also amplified the microbial colonization and enzymatic activity in soil, leading to higher microbial biomass, enhanced nutrient uptake, and reduced electrolyte leakage and osmotic potential, indicating improved plant performance. Notably, these improvements translated to higher canola seed quality, with elevated fat, ash, and fiber contents. Enhanced auxin synthesis, particularly in the presence of l-tryptophan, was linked to improved root architecture, microbial colonization, and reduced plant stress indicators. These findings suggest that biochar-microbe-l-tryptophan synergy offers a powerful tool for sustainable crop intensification in challenging soils by optimizing hormone-mediated soil-plant processes.