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Applied and Environmental Microbiology, November 2004, p. 6420-6427, Vol. 70, No. 11
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.11.6420-6427.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Escherichia coli Contamination of Vegetables Grown in Soils Fertilized with Noncomposted Bovine Manure: Garden-Scale Studies

Steven C. Ingham,1* Jill A. Losinski,1 Matthew P. Andrews,1 Jane E. Breuer,2 Jeffry R. Breuer,2 Timothy M. Wood,3 and Thomas H. Wright4

Department of Food Science,1 Hancock Agricultural Research Station,2 Lancaster Agricultural Research Station,3 West Madison Agricultural Research Station, University of Wisconsin—Madison, Madison, Wisconsin4

Received 5 March 2004/ Accepted 1 July 2004

In this study we tested the validity of the National Organic Program (NOP) requirement for a ≥120-day interval between application of noncomposted manure and harvesting of vegetables grown in manure-fertilized soil. Noncomposted bovine manure was applied to 9.3-m2 plots at three Wisconsin sites (loamy sand, silt loam, and silty clay loam) prior to spring and summer planting of carrots, radishes, and lettuce. Soil and washed (30 s under running tap water) vegetables were analyzed for indigenous Escherichia coli. Within 90 days, the level of E. coli in manure-fertilized soil generally decreased by about 3 log CFU/g from initial levels of 4.2 to 4.4 log CFU/g. Low levels of E. coli generally persisted in manure-fertilized soil for more than 100 days and were detected in enriched soil from all three sites 132 to 168 days after manure application. For carrots and lettuce, at least one enrichment-negative sample was obtained ≤100 days after manure application for 63 and 88% of the treatments, respectively. The current ≥120-day limit provided an even greater likelihood of not detecting E. coli on carrots (≥1 enrichment-negative result for 100% of the treatments). The rapid maturation of radishes prevented conclusive evaluation of a 100- or 120-day application-to-harvest interval. The absolute absence of E. coli from vegetables harvested from manure-fertilized Wisconsin soils may not be ensured solely by adherence to the NOP ≥120-day limit. Unless pathogens are far better at colonizing vegetables than indigenous E. coli strains are, it appears that the risk of contamination for vegetables grown in Wisconsin soils would be elevated only slightly by reducing the NOP requirement to ≥100 days.

* Corresponding author. Mailing address: Department of Food Science, University of Wisconsin—Madison, 1605 Linden Dr., Madison, WI 53706-1565. Phone: (608) 265-4801. Fax: (608) 262-6872. E-mail: scingham{at}wisc.edu.

Applied and Environmental Microbiology, November 2004, p. 6420-6427, Vol. 70, No. 11
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.11.6420-6427.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Unc, A., Goss, M. J. (2006). Culturable Escherichia coli in Soil Mixed with Two Types of Manure. Soil Sci. 70: 763-769 [Abstract] [Full Text]  


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