BACTERIAL GROWTH AND FUNGAL GENERA DISTRIBUTION IN SOIL AMENDED WITH SEWAGE SLUDGE CONTAINING CADMIUM, CHROMIUM, AND COPPER

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Abstract
Decomposition of sewage sludge in soil is mediated by microbial populations. The facility with which the decomposition is carried out is influenced by several factors, one being the sludge's content of toxic metals. The objectives of this investigation were to determine the effects of three concentrations, in micrograms per gram of soil, of sludge-borne cadmium (111, 1, 0.1), chromium (556, 44, 1), and copper (556, 78, 11) on bacterial numbers, ATP content, and distribution of major fungal genera in an agricultural soil suited for the disposal of sewage sludge.Bacteria were stimulated initially in the 78 and 11 μg/g Cu treatments and in the 1 μg/g Cr treatment. Restriction of bacterial growth occurred in the 556 μg/g Cu and 556 μg/g Cr treatments. Cadmium treatments exhibited counts similar to controls initially, but were reduced after 2 weeks' incubation. After 25 days, bacterial counts in controls were higher than in all but two metal treatments.Fungal intergenus relationships were altered in all but Cr treatments.ATP estimates indicated that biomass increased initially, but, by 1 week, was reduced in Cu treatments. ATP in Cr treatments paralleled the initial stimulation, but, by 2 weeks, gave lower estimates than controls. Cadmium treatments showed similar trends in bacterial counts and measured ATP.Results indicated that metal-laden sewage sludge affected soil microbial populations quantitatively or qualitatively, which could influence the capacity of these soil populations for nutrient cycling. Decomposition of sewage sludge in soil is mediated by microbial populations. The facility with which the decomposition is carried out is influenced by several factors, one being the sludge's content of toxic metals. The objectives of this investigation were to determine the effects of three concentrations, in micrograms per gram of soil, of sludge-borne cadmium (111, 1, 0.1), chromium (556, 44, 1), and copper (556, 78, 11) on bacterial numbers, ATP content, and distribution of major fungal genera in an agricultural soil suited for the disposal of sewage sludge. Bacteria were stimulated initially in the 78 and 11 μg/g Cu treatments and in the 1 μg/g Cr treatment. Restriction of bacterial growth occurred in the 556 μg/g Cu and 556 μg/g Cr treatments. Cadmium treatments exhibited counts similar to controls initially, but were reduced after 2 weeks' incubation. After 25 days, bacterial counts in controls were higher than in all but two metal treatments. Fungal intergenus relationships were altered in all but Cr treatments. ATP estimates indicated that biomass increased initially, but, by 1 week, was reduced in Cu treatments. ATP in Cr treatments paralleled the initial stimulation, but, by 2 weeks, gave lower estimates than controls. Cadmium treatments showed similar trends in bacterial counts and measured ATP. Results indicated that metal-laden sewage sludge affected soil microbial populations quantitatively or qualitatively, which could influence the capacity of these soil populations for nutrient cycling. © Williams & Wilkins 1982. All Rights Reserved.