Enhancing Lettuce Growth and Cadmium and Lead Tolerance Through Biochar and Bacteria

Soil contamination by heavy metals is a global problem that threatens human health and environmental sustainability. Biochar as an environmentally friendly soil amendment combined with bioremediation (heavy metals tolerance bacteria) as an effective and emerging strategy for sustainable remediation of heavy metals contaminated soil. Thus the objective of this research was to explore the potential of Alcaligenes Pakistanensis sp. Nov (NCCP-650) bacteria combined with biochar for remediation of cadmium (Cd) and lead (Pb) contaminated soil and its effect on lettuce growth. Biochar was applied at 0, 1, 2, 4% to Cd and Pb contaminated soil with and without bacteria in pots using lettuce as a test crop. The results of soil were recorded by analyzing different soil traits like pH, ECe, SOM, soil total N, P, K, Cd and Pb. The results revealed that, compared to single biochar amendment, biochar combined with bacteria inoculation at 4% significantly ( p < 0.05) reduced the bioavailable soil AB-DTPA extractable Cd and Pb and improved lettuce growth. The highest immobilization index of Cd and Pb was 55 and 46% in biochar treatment at 4% combined with bacteria. Similarly, Cd, Pb content in shoot and root, bioaccumulation factors values of Cd, Pb were reduced with 4% biochar applied with bacteria inoculation. The results depicted that bacteria inoculated biochar at 4% not only reduced the bioavailable fractions of Cd and Pb in soil but also positively improved plant growth and soil properties. It is concluded that biochar combined with heavy metal tolerant bacterial inoculation Alcaligenes Pakistanensis sp. Nov (NCCP-650) was most effective in reducing Cd and Pb availability to plants and enhancing plant growth compared to sole application. Hence, the application of biochar at the rate of 4% combined with Alcaligenes Pakistanensis sp. Nov (NCCP-650) inoculation is recommended for sustainable remediation of heavy metals contaminated soil.