The effects of application of sewage sludge on microorganisms in soil [microbial biomass, microbial activity, enzymatic activity, sewage sludge, heavy metals]
1981
Eiland, F. (Statens Planteavlsforsoeg, Lyngby (Denmark). Landbrugscentret)
Microbial biomass, microbial activity and enzymatic activity were determined in soil samples originating from a field experiment at the Askov Experimental Station, where sewage sludge has been applied to plots yearly since 1973. The results showed, on an average of all soil samplings, that plate counts of bacteria, biomass determined by fumigation according to Jenkinson, ATP content, oxygen uptake and dehydrogenase activity were highest in soil treated with sludge with a high content of toxic metals, lower in soil treated with sludge with a low content of toxic metals, and lowest in untreated soil (control). In contrast, plate counts of fungi were highest in soil treated with sludge with a low content of toxic metals. The untreated soil yielded intermediate values. The results from the different methods were in the same order of magnitude as previously found in other field manure experiments at the Askov Experimental Station. A toxic effect of the metal accumulation on the soil microbial activity was not observed. However, the possibility that increasing concentrations caused by repeated applications of sludge with a high metal content eventually may lead to harmful effects cannot be ruled out.
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