Red Mud (RM) and Soil Amelioration: Improvement in Soil Quality

Red Mud

The Red mud is the solid waste residue of the digestion of bauxite ores with caustic soda for alumina (Al₂O₃) production. It is a mixture of compounds originally present in the parent mineral bauxite and of compounds formed or introduced during the Bayer cycle. Red mud can be applied as soil ameliorant to acidic, sandy and micronutrient deficient soils. There are still knowledge gaps regarding the effects of red mud on the soil microbial community. According to average well color development, substrate average well color development and substrate richness 5–20% red mud increased the microbial activity of the acidic sandy soil over the short term, but the effect did not last for 10 months. Shannon diversity index showed that red mud at up to 20% did not change microbial diversity over the short term, but the diversity decreased by the 10th month. 30–50% red mud had deteriorating effect on the soil microflora. 5–20% red mud soil mixture in the low quality subsoil had a long lasting enhancing effect on the microbial community based on all parameters. However, 50% red mud soil mixture caused a decrease in diversity and substrate richness. The properties of red mud are listed in Table 1.