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

Legislation requiring the rehabilitation of new opencast coal mines ca me into effect in New South Wales, Australia, in 1973. Mining companie s now stockpile original topsoil which is later spread with fertilizer over re-shaped overburden and waste carbonaceous material. Problems i n successfully revegetating new surfaces are exacerbated by the thinne ss and infertility of natural soils, which are deficient in phosphorus and moderately acid. Revegetation has not been successful on untreate d 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 si tes having different rainfall and varying ages of rehabilitated areas, were tested for pH, EC, organic carbon, total phosphorus and availabl e aluminium. Rehabilitated areas were all characterised by very low le vels 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, hig h EC values, low total P, Al toxicity, some soil erosion and little pl ant 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.