The value of pulverized refuse fines (PRF) as a substitute for topsoil in land reclamation. 2. Lysimeter studies

Published source details Chu L.M. & Bradshaw A.D. (1996) The value of pulverized refuse fines (PRF) as a substitute for topsoil in land reclamation. 2. Lysimeter studies. Journal of Applied Ecology, 33, 858-865.
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Summary

An experiment was undertaken to assess the value of pulverized refuse fines (PRF) as a substitute for topsoil in reclamation of colliery spoil and brick waste at sites in northwest England. The pattern of growth and leaching losses from wasteland materials (colliery spoil and brick waste) fertilized, topsoiled or covered with PRF was investigated for 13 months using lysimeters.

Study sites: At Liverpool University (Merseyside, northwest England), lysemeters were installed in soil trenches. They were filled with either colliery spoil taken from Higher Folds, Greater Manchester (National Grid ref: SD 684005), or brick waste from a residential demolition site at Neston, Wirral.

Treatments: One of four treatments was applied:

i) untreated substrate (control);

ii) 15 cm layer of loam topsoil (26% sand, 48% silt, 26% clay);

iii) 15 cm PRF on the substrate;

iv) NPK (17:17:17) fertilizer applied at a rate of 50 kg/ha N. (Ground limestone at 5 t/ha was also added to the highly acidic, pH 2.9, colliery spoil).

Plastic rain gauges were installed to collect rainwater for nutrient input analysis.

Grass growth: Perennial ryegrass Lolium perenne was sown at a rate equivalent to 100 kg/ha, in May 1986 in randomized blocks (three replicates) with fertilizer treatments applied as above. The grass was harvested twice above ground level over 13 months.

Substrate samples were analysed for nitrogen content. Soil pH, organic matter content, total available nitrogen (N), phosphorus, potassium, calcium and magnesium were also determined. PRF samples from 20 cm plots (at 10 cm depth) were analysed after 3, 6, 12, 18 and 26 months to investigate mineral and mineralizable N content, and initial and final N content assessed.

Leaching losses of nitrogen, phosphorus and potassium in the first 8 months corresponded to those of leachate volume.

Initial losses of inorganic nitrogen were higher in the PRF-amended substrates, particularly colliery spoil, probably because excess nitrogen, produced through mineralization, was removed in the leachate before the prerennial ryegrass established to capture the available nutrients. Subsequent losses declined to low levels.

Phosphorus losses were greatest from fertilized lysimeters. Retention by adsorption probably accounts for the lower losses from topsoil or PRF treatment.

Total leaching losses of nitrogen and phosphorus from PRF-covered substrates were lower than those covered in topsoil.

Conclusions: The lysimeter results, combined with the sustained perennial ryegrass growth on PRF, suggests that PRF can supply adequate nutrients through mineralization and retain them effectively against leaching. The PRF used in this study therefore is an effective soil amendment in land reclamation.

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