CONDITION OF REHABILITATED COAL-MINES IN THE HUNTER VALLEY, AUSTRALIA

Legislation requiring the rehabilitation of new opencast coal mines came into effect in New South Wales, Australia, in 1973. Mining companies now stockpile original topsoil which is later spread with fertilizer over re-shaped overburden and waste carbonaceous material. Problems in successfully revegetating new surfaces are exacerbated by the thinness and infertility of natural soils, which are deficient in phosphorus and moderately acid. Revegetation has not been successful on untreated mine waste and overburden. This study provides a general overview of some aspects of post-rehabilitation soil chemistry and vegetation on these soils. A limited number of samples, collected from three mine sites having different rainfall and varying ages of rehabilitated areas, were tested for pH, EC, organic carbon, total phosphorus and available aluminium. Rehabilitated areas were all characterised by very low levels of total phosphorus, neutral pH, and variable and relatively low organic carbon, and some showed aluminium toxicity. Heavy application of gypsum at one of the steeper sites was associated with acid pH, high EC values, low total P, Al toxicity, some soil erosion and little plant cover. Except for this site, the variable vegetation cover at the sites studied seemed adequate for long-term re-establishment, despite serious weed invasion at some non-studied sites, soil loss on newly re-formed surfaces, and generally poor natural and rehabilitated soils.