Impact of co-application of biochar and <i>Pseudomonas aeruginosa</i> on microbial parameters in heavy metal contaminated soil

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The use of biochar in remediation of heavy metal contaminated soil has gained global attention in the last decade. However, there is a need for more studies on the effects and interaction of biochar and functional microbes on the resident soil microorganisms and enzyme activities in the soil. This study, therefore investigated the effects of co-application of Adenopus breviflorus (Christmas melon) derived biochar and a heavy metal tolerant Pseudomonas aeruginosa on microbial population, bacterial diversity and enzyme activities in soil artificially spiked with cadmium, copper and lead in a pot experiment. Christmas melon seeds were collected from farms in Ago-Iwoye and subjected to pyrolysis to produce biochar which were modified with acid and base. Treatments included control, acidic biochar (BA), co-application of acidic biochar and Pseudomonas aeruginosa (BAPS), basic biochar (BB), co-application of basic biochar and Pseudomonas aeruginosa (BBPS), and Pseudomonas aeruginosa (P) alone. Microbial parameters were analyzed before and after treatments. The results obtained showed that treatments, particularly BBPS and BAPs, showed significant increases in microbial populations compared to the control. The predominant bacteria isolated were Pseudomonas spp.and Bacillus spp. Catalase and urease activities varied across treatments, with BB treatment demonstrating the highest catalase activity (94.80 ± 4.90 mgKMnO4 kg-1). Urease activity was highest in the BAPs treatment (0.410 ± 0.091 mgNH4 + kg-1 h-1).In conclusion, the co-application of biochar and Pseudomonas aeruginosa reduced heavy metals, boosted microbial populations, and increased enzyme activities in the soil. This strategy holds promise for mitigating soil contamination and promoting sustainable agriculture.