Effect of amendment of bauxite processing sand with organic materials on its chemical, physical and microbial properties.
The effects of addition of a range of organic amendments (biosolids, spent mushroom compost, green waste compost and green waste-derived biochar), at two rates, on some key chemical, physical and microbial properties of bauxite-processing residue sand were studied in a laboratory incubation study. Levels of exchangeable cations were not greatly affected by additions of amendments but extractable P was increased significantly by mushroom and green waste composts and massively (i.e. from 11.8 to 966 mg P kg(-1)) by biosolids applications. Levels of extractable NO(3)(-)-N were also greatly elevated by biosolids additions and there was a concomitant decrease in pH. Addition of all amendments decreased bulk density and increased mesoporosity, available water holding capacity and water retention at field capacity (-10 kPa), with the higher rate having a greater effect. Addition of biosolids, mushroom compost and green waste compost all increased soluble organic C, microbial biomass C, basal respiration and the activities of beta-glucosidase, L-asparaginase and alkali phosphatase enzymes. The germination index of watercress grown in the materials was greatly reduced by biosolids application and this was attributed to the combined effects of a high EC and high concentrations of extractable P and NO(3)(-). It was concluded that the increases in water storage and retention and microbial activity induced by additions of the composts is likely to improve the properties of bauxite-processing residue sand as a growth medium but that allowing time for soluble salts, originating from the organic amendments, to leach out may be an important consideration before sowing seeds.
Jones
B E H
BE
School of Land, Crop and Food Sciences/CRC CARE, The University of Queensland, St Lucia, Queensland 4072, Australia.
Haynes
R J
RJ
Phillips
I R
IR
D000363:Agaricales; D000537:Aluminum Oxide / Q000737:chemistry*; D002412:Cations / Q000032:analysis*; D019069:Cell Respiration; D004798:Enzymes / Q000378:metabolism; D018525:Germination; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D031220:Lepidium sativum / Q000254:growth & development; D010758:Phosphorus / Q000032:analysis; D016062:Porosity; D059027:Recycling / Q000379:methods; D012037:Refuse Disposal / Q000379:methods*; D012822:Silicon Dioxide / Q000737:chemistry*; D012987:Soil / Q000032:analysis* / Q000592:standards; D012988:Soil Microbiology; D014867:Water
D002412:Cations; D004798:Enzymes; D007220:Industrial Waste; D012987:Soil; D014867:Water; D010758:Phosphorus; D012822:Silicon Dioxide; D000537:Aluminum Oxide