title: Cation and anion leaching and growth of Acacia saligna in bauxite residue sand amended with residue mud, poultry manure and phosphogypsum.
abstract: OBJECTIVE
  To examine (1) the effect of organic (poultry manure) and inorganic (residue mud and phosphogypsum) amendments on nutrient leaching losses from residue sand and (2) whether amendments improve the growth of plants in residue sand.
  
  
  METHODS
  Leaching columns were established using residue sand. The phosphogypsum-treated surface layer (0-15 cm) was amended with poultry manure and/or bauxite residue mud and the subsurface layer (15-45 cm) was either left untreated or amended with phosphogypsum.
  
  
  RESULTS
  Much of the Na⁺, K⁺, Cl⁻ and SO₄²⁻ was lost during the first four leachings. Additions of phosphogypsum to both surface and subsurface layers resulted in partial neutralization of soluble alkalinity. Mean pH of leachates ranged from 8.0 to 8.4, the major cation leached was Na⁺ and the major balancing anion was SO₄²⁻ . Where gypsum was not applied to the subsurface, mean pH of leachates was 10.0-10.9, the main cation leached was still Na⁺ and the main balancing anions were a combination of SO₄²⁻ and HCO₃⁻/CO₃²⁻. At the end of the experiment, concentrations of exchangeable Na⁺ in the subsurface layers were similar regardless of whether gypsum had been applied to that layer or not. Yields of Acacia saligna were promoted by additions of poultry manure to the surface layer but unaffected by gypsum incorporation into the subsurface layer.
  
  
  CONCLUSIONS
  Lack of reaction of phosphogypsum with the subsurface layer is unlikely to be a major factor limiting revegetation of residue sand since in the absence of phosphogypsum the excess Na⁺ leaches with the residual alkalinity (HCO₃⁻/CO₃²⁻) rather than SO₄²⁻.
authors: School of Land, Crop and Food Sciences/CRC CARE, University of Queensland, St. Lucia, Queensland 4072, Australia.
authors: B E H
authors: BE
authors: Jones
authors: R J
authors: RJ
authors: Haynes
authors: I R
authors: IR
authors: Phillips
mesh_terms: D000045:Acacia / Q000737:chemistry / Q000254:growth & development*; D000537:Aluminum Oxide / Q000737:chemistry*; D000818:Animals; D002133:Calcium Sulfate / Q000737:chemistry*; D002645:Chickens; D002712:Chlorides / Q000032:analysis; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005243:Feces / Q000737:chemistry*; D005308:Fertilizers; D019015:Geologic Sediments / Q000737:chemistry*; D008669:Metallurgy; D010758:Phosphorus / Q000737:chemistry*; D018517:Plant Roots / Q000737:chemistry / Q000254:growth & development; D018520:Plant Shoots / Q000737:chemistry / Q000254:growth & development; D011188:Potassium / Q000032:analysis; D012964:Sodium / Q000032:analysis; D012987:Soil / Q000737:chemistry*; D012995:Solubility; D013431:Sulfates / Q000032:analysis; D014867:Water / Q000737:chemistry; D014904:Western Australia
chemical_list: D002712:Chlorides; D005308:Fertilizers; D012987:Soil; D013431:Sulfates; D014867:Water; C077769:phosphogypsum; D010758:Phosphorus; D012964:Sodium; D000537:Aluminum Oxide; D011188:Potassium; D002133:Calcium Sulfate