Rehabilitation of bauxite residue to support soil development and grassland establishment

Rehabilitation (amendment and vegetation establishment) on bauxite residue is viewed as a promising strategy to stabilize the surface and initiate soil development. However, such approaches are inhibited by high pH, high exchangeable sodium (ESP) and poor nutrient status. Amendment with gypsum is effective in improving residue physical and chemical properties and promoting seed establishment and growth. Application of organics (e.g. compost) can address nutrient deficiencies but supplemental fertilizer additions may be required. A series of germination bioassays were performed on residue to determine candidate species and optimum rehabilitation application rates. Subsequent field trials assessed establishment of grassland species Holcus lanatus and Trifolium pratense as well as physical and chemical properties of amended residue. Follow up monitoring over five years assessed elemental content in grassland and species dynamics. With co-application of the amendments several grassland species can grow on the residue. Over time other plant species can invade the restored area and fast growing nutrient demanding grasses are replaced. Scrub species can establish within a 5 Yr period and there is evidence of nutrient cycling. High pH, sodicity and nutrient deficiencies are the major limiting factors to establishing grassland on residue. Following restoration several plant species can grow on amended residue.