Effect of electrolytic manganese residue based ecological soil on growth and root morphology of <i>Cenchrus fungigraminus</i>

To explore the resource utilization of electrolytic manganese residue (EMR), this study prepared ecological soils using EMR, red mud, and phosphogypsum as main raw materials, and conducted a pot experiment with Cenchrus fungigraminus to investigate the effects of substrate formulations on plant growth and root morphology. Results showed that pure EMR substrate failed to support bud establishment and seedling growth, while optimized formulations significantly improved establishment rate, plant height and biomass accumulation. Establishment rate of ERP1 reached 91.67%, and plant height of ERP2 was 127.50 cm. Root morphology showed high plasticity; ERP7 and ERP8 had greater total root length and surface area, with values of 1258.01, 1200.54 mm, 1285.51 and 1131.53 cm2, respectively; ERP8 exhibited the highest specific root length and specific root area, at 187.40 and 430.71 cm2/g, respectively. Correlation analysis indicated a significantly negative relationship between EMR content and growth indexes, and red mud and phosphogypsum played complementary roles in substrate improvement. Comprehensive evaluation suggested that ERP1, ERP2 and ERP6 were optimal formulations for Cenchrus fungigraminus growth. This study provides a scientific basis for resource utilization of EMR and development of industrial solid waste-based ecological soils.