Multi-nutrient leaching dynamics and phosphorus speciation in soil columns amended with fungal (Talaromyces adpressus) biomass

Abstract The development of sustainable, waste-derived fertilizers with improved nutrient use efficiency is critical for advancing circular bioeconomy strategies. This study investigated the effects of a combined sewage sludge ash (SSA) and fish meal (FM) amendment, with and without inoculation of the phosphate-solubilizing fungus Talaromyces adpressus, on soil nutrient dynamics and early plant performance. Soil column leaching assays demonstrated that fungal bioaugmentation significantly reduced cumulative nutrient losses, particularly for phosphorus (P), potassium (K), and sodium (Na), indicating enhanced retention and controlled-release behavior. Kinetic modeling revealed a shift from rapid, diffusion-dominated release in the control to delayed, regulated, and biologically mediated release in the fungal-treated system, with improved model fit and reduced variability. Importantly, these physicochemical improvements translated into enhanced biological performance. Seedling bioassays showed that the combined fungal + waste treatment achieved the highest germination percentage (100%), significantly exceeding soil-only (≈67%), waste-only (50%), and fungi-only (75%) treatments. Similarly, seedling vigor index and biomass accumulation were maximized under the combined treatment, indicating synergistic effects between fungal activity and organic amendment. These improvements are attributed to increased nutrient bioavailability, microbial production of growth-promoting compounds, and mitigation of potential inhibitory effects associated with waste-derived inputs. These findings support the design of microbially fortified fertilizers as a viable strategy for sustainable nutrient management and valorization of agro-industrial residues.