Physiological performance of Linum usitatissimum (Flax) in coal tailing-amended soils

Coal tailings (CT), a by-product of coal mining, pose environmental risks due to their acidity and heavy metal content. This study assessed the potential of using coal tailings as a soil amendment for growing Linum usitatissimum (flax), focusing on germination, biomass production, and photosynthetic efficiency. Two coal tailings from the Witbank coalfield in Mpumalanga, South Africa (Coal A and Coal B) were tested individually and in combination with soil, with and without organic fertilizer. Pure CT treatments significantly reduced germination and seedling survival possibly due to high concentrations of lead and arsenic. However, mixing CT with soil improved germination (up to 80%) and seedling establishment by reducing metal toxicity. Chlorophyll a fluorescence analyses revealed improved photosynthetic performance in soil-amended and fertilized treatments, particularly where Coal A was mixed with soil. Fertilization enhanced biomass accumulation and photosystem II efficiency, with the highest performance indices observed in fertilized Coal A + Soil. These findings suggest that soil amendments and fertilization can partially mitigate CT toxicity, offering a potential strategy for CT reuse in vegetation establishment.