Sustainable soil health enhancement in mine-affected soils: synergistic effects of vetiver grass and biochar on acidity neutralization and selected microbial population enhancement

Résumé

Mine-affected soils have the potential to alleviate pressure on food security from the rising human population. However, these soils are characterized by severe acidity, which suppresses microbial loads, limiting soil biological functioning. Consequently, this reduces their capacity to support optimum food production. Despite their potential contribution to agricultural production, the rehabilitation of mine-affected soils remains overlooked. Thus, this study evaluated the potential effect of combined vetiver grass ( Chrysopogon zizanioides ) and biochar to neutralize soil acidity and enhance soil selected microbial populations over time in gold mine-affected soils in a microplot experiment at the University of Limpopo, South Africa. Colonies of Pseudomonas spp , phosphate-solubilizing bacteria, actinomycetes, non-fastidious bacteria, and fungi were isolated from the soils before and after the experiment. Furthermore, soil electrical conductivity (EC), pH in water and potassium chloride, labile and organic carbon (SOC) were analyzed. Results revealed that mine-affected soils were initially highly acidic, with markedly reduced selected microbial populations and carbon fractions. However, the combined application of vetiver grass and biochar significantly (P<0.05) increased soil pH, SOC, and selected microbial population compared to untreated controls, with greater improvements observed at 90 days after treatment application compared to 30 days. In contrast, EC and labile carbon declined significantly (P<0.05) by day 90, likely due to increased microbial activity. Due to its liming potential and high carbon content, biochar contributed to neutralizing acidity and increasing soil carbon, while vetiver grass supported microbial recovery by improving rhizosphere conditions. These findings demonstrate that the synergy between vetiver grass and biochar offers an effective, sustainable strategy for restoring soil health in gold mine-affected soils.

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