Combined application of biochar and PGPB on crop growth and heavy metals accumulation: A meta-analysis

The combined application of biochar and plant growth-promoting bacteria (PGPB) has shown significant efficacy on alleviating plant heavy metals stress and remediating soil heavy metals pollution. Nevertheless, the underlying mechanism of the synergistic action of biochar and PGPB in the soil-plant system remain poorly understood. This investigation utilized a hierarchical meta-analysis approach to synthesize 237 datasets extracted from 59 studies, aiming to quantitatively evaluate the effectiveness of the co-application of biochar and PGPB in promoting plant growth and remediating soil heavy metals pollution. The combined treatment increased root and shoot biomass by 84 % and 116 %, respectively, while reducing heavy metal concentrations in roots (33 %), shoots (45 %), and soil (44 %). This treatment markedly enhanced plant nutrient absorption and stimulated soil enzyme induction, optimizing metabolic functions in the rhizosphere. Through comprehensive analysis of diverse plant physiological parameters, it was determined that the biochar and Pseudomonas combination exhibited optimal performance in biomass enhancement, whereas the Proteobacteria and biochar consortium had the most significant effect on decreasing the content of heavy metals in the plant and soil. Furthermore, the biochar and PGPB co-application showed the best results in mitigating Pb pollution stress. This study provides subatantive scientific basis for remediation of soil heavy metals pollution and plant stress mitigation.