Abstract
The objective of this project is to retain and maintain in good agricultural condition the long-term sludge cake and metal-amended liquid sludge experimental platforms at the seven sites in England and Wales, ahead of funding for Phase IV of the experimental programme (from April 2008). 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. This project will enable the retention 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 SEERAD) ahead of Phase IV of the experimental programme. The work addresses Defra's policy objectives of providing a sound scientific base for the continued development of policies on soil protection where sludge is applied to agricultural land (and other organic materials) by evaluating the effects of heavy metal additions on soil fertility and agricultural productivity.
United Kingdom