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Effects of sewage sludge on agricultural productivity and soil fertility (Phase III) - SP0130

Description
The overall objective of the project is to evaluate effects of the established range of soil heavy metal concentrations on soil microbial activity, the implications for agricultural productivity and long-term soil fertility.
At seven sites of contrasting clay content throughout England and Wales, selected metal rich sludge cakes were applied over a four year period (Phase I: 1994-97) to establish zinc, copper and cadmium metal dose-response curves. During phase III of the project, effects of the metal additions on soil microbial (biomass carbon, respiration and white clover rhizobia), chemical (total and extractable metals, speciation of metals, soil pH, organic carbon and cation exchange capacity) and physical properties (bulk density) will be measured. Additionally, metal uptakes into ryegrass and wheat grain will continue to be measured to quantify bioavailability of the sludge metal additions in the field, and crop yields to quantify any impacts on agricultural productivity and soil fertility.
Metal-amended liquid sludges were also applied at three sites in England over a three year period (Phase I: 1995-97) to establish zinc, copper and cadmium metal dose-response curves, and to provide contrasting metal availabilities to the sludge cake additions. The proposed programme of soil microbial, chemical and physical property determinations and crop measurements, will follow the same protocol as the sludge cake experiments.
The work addresses Government’s policy objectives of providing a sound scientific base for the continued development of policies on soil protection where sewage sludge is applied to agricultural land, by evaluating the effects of heavy metal additions in sewage sludge on soil properties (microbial, chemical and physical), agricultural productivity and long-term soil fertility.
Objective
The overall objective of the project is to evaluate effects of the established range of soil heavy metal concentrations on soil microbial activity, the implications for agricultural productivity and long-term soil fertility.

In more detail, the specific objectives of the project are:

1. To determine the effect of zinc, copper and cadmium additions in sewage sludge on soil microbial processes - biomass carbon, soil respiration and rhizobia (most probable numbers).

2. To examine the effect of zinc, copper and cadmium additions on selected soil chemical properties and speciation of metals present in soil solution.

3. To evaluate the effect of metal additions in sewage sludge on metal bioavailability to crops, agricultural productivity and long-term soil fertility.

4. To continue the annual addition of metal-rich sludge cakes on the long-term treatments at maximum permissible annual loading rates.

5. To compare the effects of zinc, copper and cadmium additions in metal-amended liquid sludges, with additions via metal rich sludge cakes, on metal bioavailability for micro-organisms and crops, agricultural productivity and long-term soil fertility (3 sites).
Project Documents
• Final Report : Effects of sewage sludge on agricultural productivity and soil fertility (Phase III)   (2177k)
• Information Leaflet : SP0130 Frequently Asked Questions   (53k)
• Information Leaflet : SP0130 Setting the Results in a Policy Context.   (54k)
• Other : SP0130 External Review Statement.   (98k)
Time-Scale and Cost
From: 2002

To: 2006

Cost: £2,281,723
Contractor / Funded Organisations
ADAS UK Ltd., Rothamsted Research (BBSRC), Water Research Centre
Keywords
Environmental Protection              
Heavy Metals              
Sewage Sludge              
Sewage Treatment and Disposal              
Soil              
Waste Management              
Fields of Study
Soil Protection