Role of biochar and PGPR in improving soil biochemical characteristics and maize growth under Cr contamination

Heavy metals toxicity in soil is increasing globally and bioremediation of these contaminants through sustainable and recalcitrant materials has gained attention in recent years. A greenhouse pot experiment was conducted to investigate the effect of Cr tolerant Bacillus subtilis and Pseudomonas aeruginosa strains along with biochar of different feedstocks on maize plant biochemical attributes and soil health. Results of the study revealed that Cr contamination decreased plant growth attributes whilst the integrated application of B. subtilis+PLB significantly improved root-shoot length (36 and 10% respectively), total chlorophyll (11.29%), and stomatal conductance (11.95%). Under Cr contamination, maize carotenoid, flavonoid, and phenolic contents also improved up to 77.20%, 39.18%, and 7.90% respectively by B. subtilis+PLB treatment. Soil PLFA content, G+, G-, Fungi and actinomycetes activity also alleviated along with antioxidants superoxidase (54%), peroxidase (28.57%), and catalase (89%) under the treatment of B. subtilis+PLB. Additionally, microbial CUE improved up to 70% under B. subtilis+PLB followed by P. aeruginosa+PLB (62%). Moreover, soil nutrient content (TOC, N, P, and K) also showed a great improvement under the combinedcombined application of PGPR and biochar. These findings of the study provide a sustainable solution for the bioremediation of Cr in agricultural soil by improving soil microbial and antioxidative activities.