title: Long-term impact of sewage sludge application on soil microbial biomass: An evaluation using meta-analysis.
abstract: The Long-Term Sludge Experiments (LTSE) began in 1994 as part of continuing research into the effects of sludge-borne heavy metals on soil fertility. The long-term effects of Zn, Cu, and Cd on soil microbial biomass carbon (Cmic) were monitored for 8 years (1997-2005) in sludge amended soils at nine UK field sites. To assess the statutory limits set by the UK Sludge (Use in Agriculture) Regulations the experimental data has been reviewed using the statistical methods of meta-analysis. Previous LTSE studies have focused predominantly on statistical significance rather than effect size, whereas meta-analysis focuses on the magnitude and direction of an effect, i.e. the practical significance, rather than its statistical significance. The results presented here show that significant decreases in Cmichave occurred in soils where the total concentrations of Zn and Cu fall below the current UK statutory limits. For soils receiving sewage sludge predominantly contaminated with Zn, decreases of approximately 7-11% were observed at concentrations below the UK statutory limit. The effect of Zn appeared to increase over time, with increasingly greater decreases in Cmicobserved over a period of 8 years. This may be due to an interactive effect between Zn and confounding Cu contamination which has augmented the bioavailability of these metals over time. Similar decreases (7-12%) in Cmicwere observed in soils receiving sewage sludge predominantly contaminated with Cu; however, Cmicappeared to show signs of recovery after a period of 6 years. Application of sewage sludge predominantly contaminated with Cd appeared to have no effect on Cmicat concentrations below the current UK statutory limit.
authors.affiliation: School of Water, Energy and Environment, Cranfield University, UK.
authors.forename: Alex
authors.initials: A
authors.lastname: Charlton
authors.affiliation: School of Water, Energy and Environment, Cranfield University, UK. Electronic address: r.sakrabani@cranfield.ac.uk.
authors.forename: Ruben
authors.initials: R
authors.lastname: Sakrabani
authors.affiliation: School of Water, Energy and Environment, Cranfield University, UK.
authors.forename: Sean
authors.initials: S
authors.lastname: Tyrrel
authors.affiliation: School of Water, Energy and Environment, Cranfield University, UK.
authors.forename: Monica
authors.initials: M
authors.lastname: Rivas Casado
authors.affiliation: Rothamsted Research, Harpenden, Herts AL5 2JQ, UK.
authors.forename: Steve P
authors.initials: SP
authors.lastname: McGrath
authors.affiliation: SRUC, West Mains Road, Edinburgh, Scotland EH9 3JG, UK.
authors.forename: Bill
authors.initials: B
authors.lastname: Crooks
authors.affiliation: James Hutton Institute, Craigiebuckler, Aberdeen, Scotland, AB15 8QH, UK.
authors.forename: Pat
authors.initials: P
authors.lastname: Cooper
authors.affiliation: James Hutton Institute, Craigiebuckler, Aberdeen, Scotland, AB15 8QH, UK; Department of Soil and Environment, Swedish Agricultural Sciences University, Uppsala, Sweden.
authors.forename: Colin D
authors.initials: CD
authors.lastname: Campbell
mesh_terms: D000383:Agriculture; D018533:Biomass; D002104:Cadmium / Q000032:analysis / Q000494:pharmacology; D003300:Copper / Q000032:analysis / Q000494:pharmacology; D004784:Environmental Monitoring; D006801:Humans; D064307:Microbiota / Q000187:drug effects*; D012722:Sewage / Q000737:chemistry*; D012987:Soil; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000494:pharmacology; D015032:Zinc / Q000032:analysis / Q000494:pharmacology
chemical_list: D012722:Sewage; D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium; D003300:Copper; D015032:Zinc
keywords: Heavy metals; Meta-analysis; Microbial biomass carbon; Sewage sludge