Temporal and environmental drivers for survival of Escherichia coli in Florida soils amended with heat-treated poultry pellets and composted poultry litter

Authors: KAPOOR, HARSIMRAN - University Of Georgia; APPOLON, CHARLES - University Of Florida; Bardsley, Cameron; KHAREL, KARUNA - Louisiana State University; SCHNEIDER, KEITH - University Of Florida; Sharma, Manan; MISHRA, ADITYA - University Of Georgia; KUMAR, GOVIND - University Of Georgia; PIRES, ALDA - University Of California, Davis; DUNN, LAUREL - University Of Georgia; MISHRA, ABHINAV - University Of Georgia

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2025
Publication Date: 10/16/2025
Citation: Kapoor, H.K., Appolon, C.B., Bardsley, C.A., Kharel, K., Schneider, K.R., Sharma, M., Mishra, A.K., Kumar, G.D., Pires, A.F., Dunn, L.L., Mishra, A. 2025. Temporal and environmental drivers for survival of Escherichia coli in Florida soils amended with heat-treated poultry pellets and composted poultry litter. Journal of Food Protection. 88(12). Article 100639. https://doi.org/10.1016/j.jfp.2025.100639.
DOI: https://doi.org/10.1016/j.jfp.2025.100639

Interpretive Summary: Biological soil amendments of animal origin (BSAAOs), like composted poultry litter and heat treated poultry-pellets, are biological fertilizers that farmers used to provide nutrients when growing fruits and vegetables. These animal manure-based fertilizers provide fertility, water holding capacity and nutrients to soils, and are a cost-effective resource for farmers. However, there is concern that these treated biological soil amendments can extend the survival of bacterial foodborne pathogens like Escherichia coli O157:H7 and Salmonella in soils, making them more likely to transfer to fruits and vegetables and causing foodborne illness in humans. In the work presented here, field experiments conducted in Florida over two consecutive years examined the survival of E. coli in soils containing composted poultry litter, heat-treated poultry pellets, or left unamended. Specifically, this study focused on the effect of weather elements like rainfall, windspeed, and soil moisture, as evaluated by a complicated statistical model (linear mixed effect model). As expected, E. coli levels in soils amended with composted poultry litter and heat-treated poultry pellets were higher than in soils that did not receive the amendments. The unique findings in this research are that cumulative rainfall events increased the survival of E. coli in soils, while wind speed events decreased the survival of E. coli in soils. ARS scientists in Beltsville collaborated on this study with two other universities. This work shows that the appropriate interval between the application of BSAAOs and harvesting of crops may need to be extended to minimize foodborne contamination if there is frequent rainfall after the application of the biological fertilizers. This work benefits American farmers by showing a specific risk factor which they can address to minimize their risk of foodborne contamination on fruits and vegetables in field agriculture.

Technical Abstract: Composted or heat-treated biological soil amendments of animal origin (BSAAOs) lower the risk of pathogen contamination of fresh produce compared to untreated BSAAOs. However, field meteorological conditions can influence pathogen survival, leading to produce contamination. A two-year field study in Florida used a completely randomized design with BSAAOs (heat-treated poultry pellets, HTPP; composted poultry litter, PL) inoculated with Escherichia coli TVS 353 alongside negative control plots without E. coli (C) and unamended plots with E. coli (UN). Additionally, 14-day-old Vidalia onion bulbs were transplanted onto selected HTPP plots (O-HTPP) and were left in the field after harvesting to cure for 14 days. Soil samples were collected on days 0, 1, 3, 7, 14, 28, 56, 84, 112, and 140 for E. coli enumeration. Additional soil samples were taken on day 147 (harvest day) and day 161 (after field curing) from the O-HTPP plots. The E. coli population data was used to fit a linear mixed effect model (LME) with five weather variables: cumulative rainfall (cmrain4), average air temperature (at601234), relative humidity (RH1234) four days before sampling; wind speed (W1); soil temperature (ast1) one day before sampling. Overall, E. coli levels were 1.8 and 1.6 log CFU/g or MPN/g higher in HTPP than UN-amended plots in Year 1 and Year 2, respectively. E. coli levels in soils significantly decreased over the experiment duration in both years, irrespective of soil amendment treatment with or without onions (p<0.05). The decline in E. coli levels was explained by different weather variables. The LME for soil amendment treatment plots identified weather parameters that significantly influenced E. coli survival; cumulative rainfall and wind speed increased and decreased E. coli survival by 0.698 and 0.712 log CFU or MPN/g (p<0.01), respectively, in Year 1. In the LME that compared HTPP plots with and without onions, wind speed significantly increased E. coli survival in soils by 0.504 log CFU or MPN/g (p<0.05) in Year 1 (p<0.05). These robust LME models (R2: 0.88-0.92) can predict the E. coli population in soils containing amendments and/or planted with onions.