Science1 publisher2 min readPublished
E. coli persists longer in Georgia onion soils amended with poultry litter
E. coli survived longer in poultry-amended Georgia onion soils than in untreated soil across two seasons, a Risk Analysis study found. Humidity went with longer survival and wind with shorter, so growers' food-safety plans may need to reflect local weather.
The Scientist · Science desk
What happened
- The longer survival in amended soil held in both growing seasons, for heat-treated poultry pellets and for composted poultry litter.
- The researchers say extreme weather events, and not average seasonal conditions alone, may shape how long bacteria survive in farm soil.
- Georgia, among the leading US poultry states, generates about 2 million tons of poultry litter a year, and the litter is widely used as fertilizer.
- Onions have been linked to major North American outbreaks, including one tied to slivered onions on McDonald's Quarter Pounders that the FDA reported in 2024.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- constraint Heat treatment and composting did not bring E. coli survival down to untreated-soil levels, so switching to a processed litter product may not by itself settle a grower's microbial risk.
- decision If extreme events matter more than seasonal averages, a fixed calendar gap between spreading litter and harvest could miss the risk, pushing growers toward plans keyed to local weather.
- precedent Regulators still gathering evidence on animal-origin soil amendments can now weigh two seasons of field data from a leading poultry state.
The study's two findings rest on different kinds of evidence. The amendment result compares amended soil against a control, soil that received no amendment, and it repeated in a second season [1][3]. The weather results are associations, and the influence of weather differed between the two seasons [4]. Two seasons is a small base for separating one weather variable from another. I would treat the weather findings as leads for a longer study.
Temperature pointed in opposite directions depending on where it was measured. Rain and warmer soil could promote persistence, the researchers found, while higher air temperatures tended to reduce survival [6]. A farm's air-temperature log would therefore capture only part of what the study tracked.
"Organic produce growers increasingly rely on biological soil amendments to improve soil health and crop productivity," Kapoor said, according to Phys.org [12]. Kapoor also said: "Our findings show that field environmental conditions and the type of amendment used can interact in ways that influence the survival of E. coli. This is important for risk-management approaches that account for local conditions." [11]
The thing this doesn't tell you is how much longer the bacteria lasted. The published summary does not report survival times in days or the size of any weather effect.
Phys.org lists onion outbreaks as context. They include a 2020 Salmonella Newport outbreak linked to red onions in the US and Canada, and a 2021 Salmonella Oranienburg outbreak tied to fresh onions imported from Mexico [14]. With the 2024 case, those incidents caused thousands of reported illnesses and hundreds of hospitalizations [15]. Salmonella is a different organism from the E. coli this study followed in soil [1].
What to watch
- Whether survival times in the full Risk Analysis paper show a gap large enough to change the interval between spreading litter and harvest.
- Whether regulators cite this Georgia field data in guidance on biological soil amendments of animal origin.
- Replication over more seasons or in other crops and regions, enough to separate the effects of humidity, rain and wind.