Synergistic Effect of Biochar, Phosphate Fertilizer, and Phosphorous Solubilizing Bacteria for Mitigating Cadmium (Cd) Stress and Improving Maize Growth in Cd-Contaminated Soil

Cadmium (Cd) contamination threatens human health and plant growth due to its accumulation in edible parts. The sole application of phosphorus-solubilizing bacteria (PSB), biochar (BC), and phosphorus (P) effectively mitigates Cd's adverse effects in contaminated agricultural systems. However, further investigation into their combined impacts on Cd toxicity and maize (<i>Zea mays</i>) production is essential. This study evaluates the synergistic effects of PSB (10 g kg^-1 of <i>Bacillus megaterium</i>), BC (5% <i>w</i>/<i>w</i>), and P (0.8 g kg^-1) on soil properties and the morphological and physiological traits of maize cultivated in agricultural soil contaminated with Cd (20 mg kg^-1). The study revealed that Cd toxicity negatively impacts soil properties, reducing shoot and root biomass, lowering chlorophyll content, and heightening oxidative stress levels. Conversely, the combined use of P, PSB, and BC markedly improved soil properties, increasing the organic matter by 175.94%, available K by 87.24%, and available P by 306.93% compared to the control. This combination also improved maize growth metrics, with increases in aboveground dry biomass (92.98%), root dry biomass (110.33%), chlorophyll a (28.20%), chlorophyll b (108.34%), and total chlorophyll (37.17%). Notably, the treatment reduced Cd concentrations in maize leaves by 61.08% while increasing soil Cd levels by 31.12% compared to the control group. Overall, the synergistic effect of P-BC-PSB is an eco-friendly strategy for mitigating Cd toxicity in contaminated soil. However, further studies are required to explore its effects and molecular mechanisms on other crops.