Abstract
The objective of this project is to: 1. Maintain in good agricultural condition the long-term sludge cake, metal-amended liquid sludge and metal salt experimental platforms at three sites (Rosemaund, Watlington and Woburn), the long-term sludge cake site at Gleadthorpe and the three mothballed sites (Bridgets, Pwllpeiran and Shirburn) upto 30 September 2010. 2. Undertake a soil sampling campaign at the Rosemaund, Watlington and Woburn sludge cake/metal-amended liquid sludge/metal salt experiments, and sludge cake experiment at Gleadthorpe in spring 2010. 3. Sieve and store the samples from the experimental sites. 4. Maintain the long-term sludge cake store at ADAS Gleadthorpe and the soil/sludge/plant sample archive at Rothamsted upto March 2011. 5. Decommission the Watlington (cake, liquid and metal salt) and Shirburn (cake) experimental platforms. At nine sites with contrasting clay contents throughout Britain, selected metal-rich sludge cakes were applied between 1994 and 1997 (Phase I) to establish individual zinc, copper and cadmium dose-response treatments. Additionally, at three of the experimental sites metal-amended liquid sludges and metal salts were applied between 1995 and 1997 (Phase I) to establish individual zinc, copper and cadmium dose-response treatments. During Phases II and III of the project (Defra projects SP0125 and SP0130), effects of the established soil metal concentrations on selected soil microbial (biomass, respiration rate and rhizobia most probable numbers), chemical (total and extractable metals, speciation of metals, organic carbon, cation exchange capacity and soil pH) and physical properties (bulk density) were measured. Additionally, metal uptakes into ryegrass and wheat grain were measured to quantify bioavailability of the metal additions in the field, and crop yields to quantify any impacts on agricultural productivity and soil fertility. Following the end of Phase III (in 2006), the long-term sludge cake, metal-amended liquid sludge and metal salt experimental platforms at the seven sites in England and Wales have been maintained in good agricultural condition. Three of the sites (Bridgets, Pwllpeiran and Shirburn) have been 'mothballed' and sown with ryegrass, with the remaining four sites (Gleadthorpe, Rosemaund, Watlington and Woburn) maintained in arable crop production.
United Kingdom