Temporal and Environmental Drivers for Survival of Escherichia coli in Florida Soils Amended with Heat-Treated Poultry Pellets and Composted Poultry Litter

Previous studies have shown that field environmental conditions influence pathogen survival in the soils amended with biological soil amendments of animal origin (BSAAOs). To address this, a two-year completely randomized design field study in Florida was conducted with plots amended with heat-treated poultry pellets (HTPPs), composted poultry litter (PL), and unamended (UN), all inoculated with E. coli. Onion bulbs were transplanted into selected HTPP plots (O-HTPP) and field cured after harvesting. Soil samples were enumerated for E. coli on days 0, 1, 3, 7, 14, 28, 56, 84, 112, 140, 147 (harvest day), and 161 (after curing). The E. coli data were used to fit a linear mixed effect model (LME) with five weather variables: cumulative rainfall (cmrain₄), average air temperature (at60₁₂₃₄), relative humidity (RH₁₂₃₄), wind speed (W₁), soil temperature (ast₁). Overall, E. coli levels were 1.8 and 1.6 log₁₀CFU or MPN/g higher in HTPP than UN plots in Year 1 and Year 2. The LME for soil amendment plots identified weather parameters that significantly influenced E. coli survival; cmrain₄ and W₁ increased and decreased survival by 0.698 and 0.712 log₁₀CFU or MPN/g (p < 0.01), in Year 1. In the LME that compared plots with and without onions, W₁ significantly increased survival in soils by 0.504 log₁₀CFU 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 amended with poultry-litter-based amendments with or without onions. However, future studies will benefit from frequent samplings at later time points.