|Liao, Ching Hsing|
Submitted to: Journal of Science, Agriculture and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2002
Publication Date: 3/12/2003
Citation: LIAO, C., HONEYCUTT, C.W., GRIFFIN, T.S., JEMISON, J.M. OCCURRENCE OF GASTROINTESTINAL PATHOGENS IN SOIL OF POTATO FIELD TREATED WITH LIQUID DAIRY MANURE. JOURNAL OF SCIENCE, AGRICULTURE AND ENVIRONMENT. 2003. V. 1 (2). P. 224-228. Interpretive Summary: Liquid dairy manure (LDM) is commonly used as fertilizer supplement to improve crop production and has been shown to harbor bacteria (pathogens) capable of causing illness in humans. Application of inadequately prepared manure thus becomes a potential route for transmission of human pathogens to crops on the farm. Understanding the survival kinetics of pathogens in soil treated with manure is important for determining the timing for safe application of manure. In this study, four different types of manures were analyzed for the presence of three major foodborne pathogens previously found to be associated with fresh produce. One of them known as Listeria monocytogenes was consistently detected in LDM-treated soil during the first 6 to10 weeks after LDM application. However, the pathogen population declined very rapidly and became undetectable approximately 10 weeks after LDM application. No pathogen was detected on potato tubers grown in LDM-treated soil. This study suggests that proper and thorough composting of manure and incorporating it into soil at least 12 weeks prior planting are important steps toward reducing the risk of pathogen contamination.
Technical Abstract: In parallel with a study of liquid dairy manure (LDM) effects on potato (Solanum tuberosum) production, an investigation was conducted to monitor the occurrence of three major foodborne pathogens in soil amended with LDM under field conditions. LDM was added prior to planting potatoes in experimental plots (randomized complete block design, 5 replications) in 1999 and in 2000. Soil samples were collected periodically from plots treated with or without LDM and analyzed for the presence of Listeria monocytogenes, Salmonella sp., generic Escherichia coli, and E. coli O157:H7. In the 1999 potato-growing season, L. monocytogenes was consistently detected in LDM-treated, but not in untreated, soil samples during the first six weeks after LDM application. However, L. monocytogenes became undetectable approximately ten weeks after LDM application. A rapid decline in the number of generic E. coli, from 292 cfu g-1 soil in June to 10 cfu g-1 soil in July, was also observed. Salmonella and E. coli O157:H7 were not detected in 120 soil and potato samples analyzed. In the 2000 potato- growing season, no pathogen was detected in 60 soil and potato samples analyzed, although generic E. coli was detected once at a very low level (2 cfu g-1 soil). This study indicates that L. monocytogenes can be present in soils during the first 40 to 70 days after LDM application.