Physical properties exhibited by unvegetated mine wastes pose limitations to vegetation establishment and growth. In an attempt to promote vegetation cover on bauxite residue, a field trial was established to determine the effect of spent mushroom compost (SMC) and gypsum amendment on enhancing the physical properties of the residue. SMC was incorporated at rates of 0, 60, 80 and 120 t ha À1 with gypsum at 0, 40 and 90 t ha À1 and Holcus lanatus sown at a rate of 80 kg ha À1 . The addition of SMC and gypsum was beneficial in improving the physical properties of the residue and promoting growth. Principally increasing organic content of the residue decreased bulk density and particle density whilst improving substrate porosity. Residue pH, EC and sodicity of the residue were also affected by the amendments, which positively impacted on microaggregate stability and preventing clay dispersion. Pearson correlations demonstrate that the most significant parameters in determining clay dispersion potential are the pH and the exchangeable sodium percentage (ESP) of the residue.

Spent mushroom compost (SMC) has proven to be an attractive material for improving soil structure in tilled soils and increasing dry matter production in grassland soils, owing to its high organic matter content and availability of essential plant nutrients. Because of this, it is important to identify the variability in composition of SMC in order to evaluate its merit as a fertilizer/soil conditioner. For this reason, a study was carried out involving the analysis of SMC samples obtained from five mushroom growers using compost from each of the 13 mushroom composting yards currently operating in both Northern Ireland (5 yd) and the Republic of Ireland (8 yd). The selected parameters measured include dry matter, organic matter, total N, P and K, C/N ratio; plant-available P and K, pH, EC, total Ca, Mg, Na, Cu, Zn, Fe, Mn, Cd, Cr, Ni, Pb; and cellulose, hemicellulose and lignin constituents. Yield of mushroom data were also collected from the selected growers. There were significant differences (P<0.05) within two compost production yards for some parameters, therefore, for the most part, the uniformity of SMC within each yard is relatively consistent. However, significant differences (P<0.05) were evident when comparing SMC obtained from growers supplied with compost from Northern Ireland and the Republic of Ireland independently, particularly among total and available phosphorus and potassium values. The results obtained show that, while SMC has fertilizer merit, its variability of composition must be taken into account when assessing this value. The variability of composition is also of particular interest in the context of recent emphasis on plant nutrient management in agriculture.

In an attempt to promote sustainable vegetation cover on metalliferous tailings, a randomized factorial greenhouse trial of six-month duration was established to determine the effect of spent mushroom compost (SMC) amendment on the physical and chemical properties of the predominantly lead/zinc tailings. The tailings originated from the surface (20-30cm) of the partially-vegetated 76ha tailings management facility (TMF), where more than nine million tonnes of pyritic metalliferous material were deposited in an unlined land impoundment. SMC was incorporated at application rates of 0, 50, 100, 200 and 400tonha(-1), with each treatment replicated 10 times and Lolium perenne sown at a rate of 200kgha(-1). The addition of SMC was beneficent as a growing medium through improvement of the structural status of the tailings and ultimately through the provision of plant nutrients and reduction in metal concentrations. However, this improvement in the structural and chemical status of the tailings is not adequate in maintaining a sustainable vegetation cover and therefore other remedial options such as introducing a capillary break on the surface of the tailings facility are necessary.