Eragrostis curvula cultivars reduce aluminium concentrations and promote the proliferation of beneficial bacteria in acidic ecosystem soils

Soil acidity and aluminium (Al) toxicity are global challenges that negatively affect soil health, plant growth, and agricultural productivity. Eragrostis curvula, a grass species known for its Al tolerance, presents a promising solution for mitigating soil Al toxicity and restoring soil health. However, limited research exists on whether E. curvula cultivars accumulate Al, how they reduce soil Al concentrations, and how they contribute to soil health following remediation. This study investigated Al accumulation across various growth stages of E. curvula cultivars (Ermelo and Agpal) and characterised changes in soil bacterial communities. Acidic, Al-toxic soils were collected from Jameson Park, Kaydale, and Rensburg in Heidelberg, South Africa. Aluminium concentrations in plant tissues and pre- and post-harvest soils were analysed, bioconcentration factors were calculated to evaluate Al accumulation efficiency, and bacterial isolates from pre- and post-harvest soils were identified. Results showed that soil Al concentrations decreased substantially, from 58 533-65 096 mg/kg pre-planting to 22 301-36 407 mg/kg post-harvest, while soil pH increased from 4.72 to 5.63. The Ermelo cultivar accumulated between 21 961.7 and 40 106.2 mg/kg Al, with bioconcentration factors ranging from 0.06 to 0.66 (five-day harvest), 0.19-0.57 (inflorescence harvest), and 0.25-0.62 (maturity harvest), while Agpal accumulated 9 446.9-28 735.4 mg/kg with bioconcentration factors of 0.13-0.32, 0.02-0.17, and 0.06-0.73 for the same stages. Post-harvest soils were enriched with beneficial bacterial genera, including Paraburkholderia, Bacillus, Pantoea, Pedobacter, Achromobacter, Pseudoarthrobacter, Erwinia, Providencia, Arthrobacter, and Flavobacterium, which are associated with key plant growth-promoting traits such as nitrogen fixation, phosphorus solubilisation, stress tolerance, and biofilm production. These findings demonstrate that E. curvula cultivars accumulate Al at varying efficiencies across growth stages and reduce soil Al levels, improve pH, and enhance microbial communities, underscoring their potential in remediating acidic, Al-toxic soils and promoting sustainable soil health.