Southern soils mitigate manure microbes

Tuesday, November 2, 2010

A U.S. Department of Agriculture study in Mississippi shows that swine manure doesn't appear to bring dangerous bacteria to soils when it is spread on fields and used to grow hay, a common southern U.S. practice.

The fields tested – on five farms and 20 soil types – had been sprayed with manure for 15 years or more. There was no difference in the amount of E. coli and Enterococcus found in sprayed and unsprayed fields. Campylobacter and Salmonella enteritidis could not be cultured in a significant amount from the spray fields. An analysis of data from three public health districts found no difference in the number of reported disease incidence between areas with concentrated animal feeding operations and those without.

Team microbiologist John Brooks said: "Finding similarly low levels inside and outside the spray fields suggests that the low levels of pathogens in [manure] are further diluted in spray fields and either do not survive in soil or survive at low levels below cultural detection limits."

The results were published in the September-October issue of the peer-reviewed Journal of Environmental Quality, published by the American Society of Agronomy, Crop Science Society of America and the Soil Science Society of America. BF