Rhizosphere dynamics in soil recovery by Leucaena leucocephala mining tailing-contaminated substrates from the Fundão Dam failure.

One alternative for soil quality restoration is the use of microorganisms that enhance plant development and contaminant bioavailability. This study evaluated the microbial community in the absence and presence of Leucaena leucocephala cultivated in mining tailings from the Fundão Dam collapse, Mariana, Brazil. Substrates included 0, 25, 50, 75, and 100% tailings. Plant growth, total organic carbon (TOC), respiration, and rhizosphere prokaryote density were analyzed. Plant development decreased with higher tailing proportions, while TOC increased in the presence of leucaena. Comparisons between treatments with and without leucaena revealed higher TOC in 0 and 50% tailings. Microbial activity, measured as CO₂ release, was maintained in 25% tailings, matching the control. Prokaryote density was similar across all treatments with leucaena; among tailing treatments, only the 25% condition was statistically comparable to the substrate without tailings. These results indicate that L. leucocephala contributes to improving organic carbon and sustaining microbial communities under tailing-contaminated conditions. Recovery of microbial activity is more effective when tailings are mixed with fertile substrates, highlighting the potential of combining plants and microbial processes for bioremediation of degraded areas.