Biochar-mediated recovery of soil–wheat systems under heavy metal stress: toward sustainable development goals

This study evaluated the effectiveness of biochar application in mitigating heavy metal and improving wheat (<i>Triticum aestivum</i> L.) performance grown under Pb-, Cd-, and Zn-contaminated soil. Two biochar application rates (20 and 30 t ha^-1) were applied to assess their effects on heavy metal behavior, plant physiological responses, antioxidant defense mechanisms, growth and yield attributes. Biochar amendment significantly reduced Pb and Cd concentrations in soil and wheat tissues, indicating decreased metal bioavailability and restricted plant uptake. In contrast, Zn exhibited a variable response depending on biochar rate, reflecting its dual role as an essential micronutrient and its sensitivity to soil chemical changes. Biochar application improved photosynthetic pigment contents and enhanced wheat growth parameters, including stem length, spike length, biomass, and grain yield. Antioxidant responses revealed contrasting trends among enzymes: while CAT, APX, and POX activities increased markedly under biochar treatments, SOD activity declined, suggesting reduced oxidative stress intensity. Multivariate analyses (principal component analysis, correlation, and regression) confirmed strong associations between biochar application, reduced metal accumulation, enhanced physiological performance, and improved growth traits. Overall, these findings highlight biochar as an effective and sustainable soil amendment that enhances crop resilience, limits heavy metal mobility, and supports environmentally sustainable agricultural production in metal-contaminated soils.