The maintenance of grassland on smelter wastes in the Lower Swansea Valley. II. Copper smelter waste.
Large-scale grassland trials, using applications of organic materials and pulverized fuel ash on copper smelter waste, were set up in the Lower Swansea Valley in 1965 and monitored until 1970. Pasture growth on most of the treatments declined markedly in 1968 and 1969. Annual applications of fertilizer failed to prevent this decline, which was attributable to the recurrence of copper toxicity. The most successful treatment in the long term was a 22.5 cm covering of pulverized fuel ash, followed by annual NPK fertilization. Initial applications of 5 cm layers of sewage sludge, or domestic refuse, or 7.5 and 15 cm layers of pulverized fuel ash, gave satisfactory cover of pasture at first but were not satisfactory in the long term.