Composts of poultry litter or dairy manure differentially affect survival of enteric bacteria in fields with spinach

The aim was to determine the survival and persistence of Escherichia coli in soil amended with compost from different manure sources.

Complex interactions of abiotic and biotic factors on E. coli survival were characterized in field experiment plots receiving randomly assigned compost treatments: dairy windrow, dairy vermicompost, poultry windrow or no compost. Biomass, activity and function of indigenous microbial communities in the composts and soils were measured concurrently to determine whether mechanisms of compost were driven by biotic or abiotic properties. E. coli persisted in compost containing poultry amendments but not in composts containing dairy or no amendments. Poultry compost contained more NH₄ -N and a distinct microbial community compared to dairy and no compost treatments. A laboratory experiment performed on compost extracts suggested that E. coli survived better in extracts devoid of indigenous microbes as long as bioavailable nutrients were plentiful.

Dairy-based composts are less likely to support E. coli survival than poultry-based composts.

Results aid in risk assessment of the use of different types of manure-based compost and soil amendments in fruit and vegetable production by elucidating the roles of nutrient and microbial community composition on survival of E. coli in amended field soils.