Individual study: Maintenance of sown grassland on blast furnace slag waste through pulverized fuel ash and fertilizer addition in the Lower Swansea Valley, Glamorgan, Wales
Gemmell R.P. (1976) The maintenance of grassland on smelter wastes in the Lower Swansea Valley. I. Blast furnace slag. Journal of Applied Ecology, 13, 285-294
Reclamation trials, using applications of organic materials and pulverized fuel ash, combined with sowing of grasses, aimed at establishment and maintenance on blast furnace slag were set up on copper smelter waste in the Lower Swansea Valley, Glamorgan (south Wales) in 1965 and monitored until 1970.
Separate 0.1 ha areas were treated with 1,000 kg/ha of 10:10:18 NPK fertilizer and either: sewage sludge of domestic refuse (applied as layers about 1.3 cm deep), or no further treatment (‘nil’). A further area was amended with pulverized fuel ash (PFA) (7.5, 15 or 22.5 cm deep layers) and 500 kg/ha of 20:10:10 NPK fertilizer.
Sewage sludge, refuse and nil plots were sown to each of three sward types: common bent-grass Agrostis (capillaris) tenuis, red fescue Festuca rubra or a complex grass ley (perennial rye-grass Lolium perenne 14%; Italian rye-grass Lolium multiflorum 12%; cock’s-foot Dactylis glomerata 50%; timothy Phleum pratense 8% - F.rubra 10%; red clover Trifolium pratense 6%). PFA plots were sown with a mix of perennial rye-grass (40%) red fescue (30%) and red clover (30%).
Seeding (rate 67 kg/ha) was carried out at the end of May 1965. In 1966 fertilizer application and cutting treatments (cut once in autumn or cut in June and autumn, cut material removed) commenced. NPK fertilizer was applied annually to half of each plot (at 600 kg/ha), the other half received no fertilizer. In spring 1968, a soil addition treatment (4 m³/ha applied to half of each plot) was applied, the aim being to introduce soil micro-organisms.
Dry matter production and species composition were measured at intervals. Notes were also made of visual appearance, weed infestation and nutrient deficiency symptoms.
Red fescue, without or without organic amendments, performed well in the long-term if fertilizer was added annually. Conversely, the mixed swards performed well initially if no fertilizer was added but ultimately were poorer. Common bent grew well initially, especially on sewage sludge plots, but by 1969, weeds and the other swards had encroached upon these plots. Perhaps common bent declined due to the alkaline soil conditions that red fescue is able to tolerate and additionally performs better on dry soils.
Maintaining soil fertility was important. In the long-term, annual fertilizer applications were effective in maintaining fertility and sustaining high grass and clover yields. Initial fertilization (only) appeared inadequate. Also, without sludge or refuse addition, mixed swards declined in yield by about 50% from 1966-9. This was most pronounced for twice annually cut plots with initial fertilization only. Low yielding red fescue became dominant at the expense of the more productive Dactylis, Phleum and Lolium. Evidence from observations in 1969, suggest that the species composition of mixed swards is a simple fescue/clover association.
There appeared little or no advantage in using PFA as a substitute for organic amendments, and perhaps neither amendments are necessary unless aims are to produce large yields and to maintain the more productive grass species. There was some evidence that cutting enhanced productivity and that it maintained soil fertility, and was valuable for weed control.