Field scale assessment of artificial topsoil: a Victorian coal mine experience

The Latrobe Valley is host to several open-cut coal mines which pose an environmental risk if poorly managed. To reduce risks associated with acid mine drainage and fire, progressive rehabilitation of batters is recommended. A lack of topsoil in the Latrobe Valley has led an industrial symbiosis to generate artificial topsoil’s (ATS). Based on previous experiments, three ATS were created by combining overburden (OB), brown coal (BC), fly ash (FA) and one of the two waste products from a local paper mill – Effluent Sewage Recovery (ESR) or Enviroshield (ES). The ATS were compared to a local topsoil (TS). The study analyzed the physical and chemical properties of the topsoil’s, seed germination and grass establishment. It was found that all ATS had similar properties and were alkaline compared to an acidic TS. The ATS were enriched in salts and found to be sodic to highly sodic and highly saline while TS was non-saline but slightly sodic. The ATS were also low in nitrogen and, due to the high pH of the soil, nutrients such as phosphorus, iron and manganese were not bioavailable. For the duration of the study, germination and grass establishment on ATS was not significant, however, grass was beginning to establish on the TS. As such, it is recommended further investigation be undertaken to determine an appropriate seed mix for the ATS which is tolerant to alkaline and saline soils. Further research is being conducted to determine the source of the alkalinity and salinity in the ATS.