Substrate utilisation profiling of microbial communities in sewage sludge amended soils
The aim of this thesis was to use long-term sewage sludge application to land to determine if sludge, particularly metal-rich sludge, alters the microbial community as indicated by substrate utilisation profiles (sups), using the Biolog TM method. An additional aim was to assess BiologTM as a rapid method of monitoring soil health. Sludge rich in Cadmium altered microbial community profiles, but this was possibly due to differences in organic Carbon quality between sludges used in the trial. Conditioning (incubation) of soils before analysis with BiologTM made these effects more apparent. Storage of soil also altered microbial activity and community profiles, which were not restored by a conditioning period. Both incubation and storage influenced the BiologTM response and can potentially affect available soil C. Therefore, the effects of organic matter application at high levels on the microbial community, were assessed without metals. Low metals sludge altered microbial community function, although the trends were not consistent across soil types. BiologTM was more sensitive to sludge treatment effects than total microbial biomass C. The microbial community responses to sludge and preparation disturbance were examined (using BiologTM and microbial PLFAs). A method to determine extractable carbohydrates was adapted for use in a microplate format, and was employed to assess the relationship between microbial community change and available soil C. Changes in soil microbial community structure and function were not related to extractable carbohydrate C. BiologTM and PLFA responded differently: disturbance had a greater effect on Biolog response than either application of sewage sludge or the quality of soil C; but PLFAs were more affected by long-term sewage sludge amendment, highlighting implications for the monitoring of waste-amended soils.