Cultivar-Specific Effects of Mustard Green Biofumigation on Salmonella enterica Newport Survival in Soil Microcosms.

Brassicaceae cover crops are widely used to improve soil health and provide multiple agronomic benefits. The use of Brassica juncea, oilseed mustard, as a biofumigant to suppress soilborne pests and pathogens is well studied, but data are needed on their impacts on foodborne pathogens in agricultural soils. This study evaluated the cultivar-specific effects of eight mustard varieties on Salmonella enterica survival in soil microcosms. Eight cultivars were grown in a certified organic field, harvested at flowering, chopped, and incorporated into soil inoculated with rifampicin-resistant Salmonella enterica serovar Newport J1892 to an initial concentration of ∼8 log CFU/g. Microcosms were established for each cultivar along with an unamended control, and populations were enumerated on days 0, 1, 4, and 7. Salmonella populations increased from day 0 to day 1 across all treatments, including the control (p < 0.05). Over the 7-day sampling period, the untreated soil showed the highest reduction (1.56 log CFU/g), and the mustard-amended soils showed smaller reductions (≤0.72 log CFU/g). Salmonella die-off rate was higher in untreated soil (0.57 log CFU/g/day), while soils incorporated with mustard plants showed comparable or lower die-off rates (0.18-0.40 log CFU/g/day). Results from this study suggest that biofumigation with mustard may not provide reliable short-term suppression of Salmonella in agricultural soil.