Abstract
The objective of this project is to retain and maintain in good agricultural condition the long-term sludge cake, metal-amended liquid sludge and metal salts experimental platforms at the seven sites in England and Wales. 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 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. Between April 2009 and March 2010 the long-term sludge cake, metal-amended liquid sludge and metal salt experimental platforms at the seven sites in England and Wales will be maintained in good agricultural condition. Three of the sites (Bridgets, Pwllpeiran and Shirburn) will be 'mothballed' and sown with ryegrass, the remaining four sites (Gleadthorpe, Rosemaund, Watlington and Woburn) will continue to be maintained in an arable system. This project will enable the continuation and maintenance of the experimental platforms in good agricultural condition at the seven research sites in England and Wales (the two Scottish sludge cake sites are funded separately by the Scottish Government). Additionally, planning work will be undertaken ahead of the next full sampling phase, which will take place in spring 2010.
United Kingdom