Growth and nutrition of Holcus lanatus in bauxite residue amended with combinations of spent mushroom compost and gypsum

Bauxite residues are very slow to naturally vegetate due to nutrient deficiency and high sodicity. In order to test the effectiveness of amendments at promoting revegetation, bauxite residue was amended with varying rates of compost to increase fertility (0, 60, 80 and 120tha ^-1) and gypsum to reduce sodicity (0, 40 and 90tha ^-1). Amended residue was sown with Holcus lanatus, a perennial grass. Following a 1-year growth period, substrate properties, plant performance and plant nutrient uptake were assessed. Compost application substantially increased substrate N, P, K and Mn concentrations, while gypsum application greatly reduced sodicity and improved nutrient uptake for Mn and P. Compost amendment was essential for sustainable plant growth. Foliar deficiencies in N, P and Mg may persist with lower compost application rates, requiring the addition of supplemental fertiliser for healthy plant growth.