Comparing the Survival of Salmonella in Soils Amended with Pecan Shells and Poultry Manure

Pecan shells have antimicrobial properties but are generally viewed as a waste product that is often discarded. Poultry manure is often used as a soil amendment but has been shown to promote the survival of foodborne pathogens in the soil. The objective of this research was to first compare the die-off of Salmonella in inoculated ground pecan shells and poultry manure, and then to evaluate its survival in soils amended with pecan shells, poultry manure, or a mixture of both pecan shell and poultry manure, compared with unamended soil. Inoculated ground pecan shells and poultry manure were enumerated at 0, 1, 3, 7, 10, 14, 21, and 28 days postinoculation. Soil treatments (unamended, pecan shell amended, poultry manure amended, and mixed) were inoculated with Salmonella and enumerated at 0, 1, 3, 7, 10, 14, 21, 28, 42, and 56 days postinoculation. Die-off models were generated using GInaFit. A more rapid Salmonella die-off was observed in poultry manure compared to ground pecan shells, with reductions of 5.28 and 1.70 log by day 14, respectively. The die-off data were best fit to a Weibull model with shape parameter (p) values of 1.63 ± 0.12 and 0.39 ± 0.02 in poultry manure and ground pecan shells, respectively. In soil, a higher initial Salmonella die-off was observed in the pecan shell amended treatment; however, by day 56, the greatest reduction occurred in the unamended soil (5.09 log CFU/g), followed by the pecan shell amended (3.94 log CFU/g), mixed (2.85 log CFU/g), and the poultry manure amended (2.81 log CFU/g) soils. A biphasic model was the best fit for the soil treatment data. The results of this study show that pecan shells could be a potential soil amendment that can promote soil health and provide soil nutrients, while, unlike poultry manure, not promoting the survival of Salmonella in soil.