Dynamics of Escherichia coli in agricultural soils receiving swine manure slurry or liquid municipal biosolids

Abstract

The fate of two E. coli stains, one that grows in soil receiving swine manure slurry (SMS) (Strain C279) and one that does not (Strain C278) were evaluated in laboratory and field experiments. A sensitive (detection limit 5 cells g soil-1) microplate-format most probable number (MPN) method for enumerating E. coli was developed and validated. In laboratory incubations, there was a general relationship between manure volatile fatty acid (VFA) content and the ability of the SMS to support growth in soil. Strain C279 grew in SMS-amended loam or sandy soil, but not in silt loam soil. Swine manure slurry inoculated with both Strains C278 and C279 was surface or subsurface applied in field microplots. The population of E. coli increased 50-fold within 3 d, and the ratio of Strain C279 to Strain C278 increased as much as 20-fold during the experiment, consistent with the growth of Strain C279 under these circumstances. Liquid municipal biosolids (LMB) obtained from four cities did not support the growth of Strain C279. The dynamics of E. coli populations in soils receiving surface and subsurface (10 cm) applications of SMS were comparable. Key words: Escherichia coli, water quality, liquid municipal biosolids, swine manure slurry