Survival of Escherichia coli in manure-amended soils is affected by spatiotemporal, agricultural, and weather factors in the Mid-Atlantic United States

Authors: Sharma, Manan; Millner, Patricia; HASHEM, FAWZY - University Of Maryland Eastern Shore (UMES); VINYARD, BRYAN - US Department Of Agriculture (USDA); East, Cheryl - Roberts; Handy, Eric; White, Kathryn; STONEBRAKER, RICHARD - University Of Maryland Eastern Shore (UMES); COTTON, CORRIE - University Of Maryland Eastern Shore (UMES)

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2018
Publication Date: 2/21/2019
Citation: Sharma, M., Millner, P.D., Hashem, F., Vinyard, B.T., East, C.L., Handy, E.T., White, K.E., Stonebraker, R., Cotton, C.P. 2019. Survival of Escherichia coli in manure-amended soils is affected by spatiotemporal, agricultural, and weather factors in the Mid-Atlantic United States. Applied and Environmental Microbiology. 85:e02392-18. https://doi.org/10.1128/AEM.02392-18.
DOI: https://doi.org/10.1128/AEM.02392-18

Interpretive Summary: Animal manure used as fertilizer in soils used to grow fruits and vegetables can contain bacterial pathogens. To minimize the risk of transfer of pathogens from manure-amended soils to crops intend for human consumption and potential for foodborne illness, current language in the Food Safety Modernization Act’s Produce Safety Rule states no objection to a 90 or 120-day interval between application of manure (untreated biological soil amendments) to soils and harvest of crops (BSAAO). Our regional multiple season, multiple location field trial determined survival durations of E. coli in soils amended with manure to determine if this interval is truly appropriate for the Mid-Atlantic region of the U.S. In the 12 separate field trials and 324 E. coli survival profiles which were conducted in our study, spatiotemporal factors (site of field, year of manure application, season of application) influenced survival durations of E. coli more than amendment type (poultry litter, horse manure, dairy manure), total amount of E. coli present, organic or conventional soil management, and depth of manure application. Poultry litter supported extended survival of E. coli in amended soils compared to other manure types amended to soils, but spatiotemporal factors may have more influence than manure type in supporting survival of E. coli in amended soils beyond a proposed 90-day interval in the Mid-Atlantic U.S. This research benefits federal regulators (Food and Drug Administration) and farmers by providing data from field trials which shows that in particular seasons at particular locations in the Mid-Atlantic region, survival of E. coli can exceed the 90-day interval between manure application and harvest of crops intended to minimize foodborne illness.

Technical Abstract: Untreated biological soil amendments of animal origin (BSAAO), like manure, are commonly used to fertilize soils for growing fruit and vegetable crops, can contain enteric bacterial foodborne pathogens. Little is known about the comparative longitudinal survival of pathogens in agricultural fields containing BSAAO, and field data may be useful to determine intervals between manure application and harvest of produce intended for human consumption to minimize foodborne illness. Our study generated 324 survival profiles from 12 different field trials at three different locations (UMES, PA, BARC) in the Mid-Atlantic U.S. from 2011-2015 of inoculated non-pathogenic (gEc) and attenuated-O157 E. coli (attO157) in soils which were unamended (UN), amended with poultry (PL), horse manure (HM), dairy manure soils (DMS) or liquids (DML). Site, season, inoculum level (low/high), amendment type, management (organic/conventional), and depth (surface/tilled) all significantly (p < 0.0001) influenced survival duration (dpi100mort). Spatiotemporal factors (site, year, season) in which the field trial was conducted influenced dpi100mort of gEC and attO157 to a greater extent than weather effects (average daily temperature, rainfall). Initial soil moisture content was the single factor which accounted for the greatest percentage of variability in dpi100mort. PL supported greater dpi100mort of gEC and attO157, followed by HM, UN, and DMS in amended soils. Most gEc and attO157 survival profiles which survived for greater than 90 days came from a specific year (2013). The effect of management and depth on dpi100mort were dependent on the amendment type evaluated.