Pasture establishment and fertiliser requirements on rehabilitated land after opencast coal mining in New Zealand

Existing pasture establishment practices to rehabilitate land after opencas t mining in the Waikato coal fields area of New Zealand were examined and c ompared with an alternative method involving different pasture mixtures, se eding rates, and lime and fertiliser requirements. Pasture establishment an d production, botanical composition changes, and plant and soil nutrient st atus were measured during a 2-year field trial. Highly significant pasture responses were obtained to increased fertiliser inputs. Heavy rates of fert iliser (1000 kg ha(-1) superphosphate) were required to raise Olsen P soil levels during the establishment phase whereas half that rate was found to b e sufficient for the maintenance phase. An improved seed mixture, containin g superior pasture cultivars, established more quickly and out-yielded the existing seed mixture by 58%. The two seed mixtures responded differently t o sowing rates; the higher rate increased pasture yields of the improved pa sture species but decreased the existing seed mix yields. Liming at 5 t ha( -1) significantly increased soil pH and clover content and reduced pasture manganese concentrations from possibly toxic levels. Nitrogen concentration s in pastures were below optimum throughout the trial and the strategic use of nitrogen fertiliser is recommended as a useful management option.