Survival of faecal indicator bacteria in bovine manure incorporated into soil

Aims: Survival of Escherichia coli and enterococci was evaluated in bovine manure incorporated into two Wisconsin soils. Methods and Results: Silty clay loam (SCL) and loamy sand (LS) were mixed w ith fresh bovine manure, exposed daily to 10 h at 22 degreesC/14 h at 9 deg reesC, and watered weekly for 12 weeks. Escherichia coli numbers increased 1-2 log cfu g(-1), then decreased < 1 and about 2 log cfu g(-1) in SCL and LS, respectively. Enterococci numbers rose less and then declined faster th an those of E. coli. Watering intervals of 3, 7 and 14 days were evaluated in weeks 13-19, but did not affect the slow decline in numbers of E. coli o r enterococci. Conclusions: Escherichia coli and enterococci may survive at least 19 weeks at 9-21 degreesC in bovine manure/soil, with E. coli surviving better. Significance and Impact of the Study: Quantification of E. coli or enteroco cci in late spring/early summer soil may be useful in indicating recent app lication of bovine manure.