EFFECTS OF SEWAGE SLUDGE APPLICATION ON SOIL MICROBIAL PROCESSES AND SOIL FERTILITY
Report No FR0034

S R SMITH

Oct 1989

SUMMARY

I OBJECTIVES

To describe the effects of increasing soil metal concentration by sewage sludge application on soil microbial processes in relation to the fertility of soils used for agriculture.

To determine the agronomic significance of particular soil microbial processes.

To establish a strategy for further research so as to provide a sound basis for the long term security of sludge recycling to agricultural land.

II REASONS

There is increasing concern that the application of sewage sludge to agricultural land, even within current maximum limits for soil metal concentrations, may have long-term deleterious effects on soil micro-organisms and soil fertility.

III RESUME OF CONTENTS

Reported evidence of effects of heavy metals on soil microbial processes is highly contradictory. Current knowledge of effects of heavy metals on soil microbial processes is reviewed. Elevated soil metal concentrations have been shown to select ineffective strains of micro-organisms, and reduce rates of microbially mediated processes. Potentially, these effects could be of agronomic significance. However, soil microbes have been shown to develop tolerance to elevated soil metal conditions without loss of function. Effects of metals on soil microbes have only been studied for a limited number of sludged sites and further research is required to determine the overall impact on agriculture of metal effects on soil micro-organisms

Copies of the Report are available from FWR, price 15.00 less 20% to FWR Members