Purpose: To assess the influence of sustainable farming practices (cover crops, solarization and dry-wet events) on the survival of Salmonella in soils.
Methods: Microcosm, mesocosm, and field studies were established using clay and loam soils. Avirulent (field) and pathogenic (greenhouse) strains of Salmonella Typhimurium were inoculated into un-composted chicken litter at log 2, 4, and 6 CFU/g and incorporated into soil. Survival was assessed after growing+discing spinach, followed by cover cropping, solarization, and dry/wet events. The survival of Salmonella was assessed after each inoculation and intervention event for up to 90 days. The influence of secondary cover crop metabolites on the survival of Salmonella was assessed under the experimental systems.
Results: Microcosms: Significant negative correlations were established between the population of Salmonella, temperature, and time (P < 0.05) while positive correlations were found between Salmonella populations and soil moisture content (P < 0.05). Greater death rates were observed in loam than clay soils (P < 0.05). Inhibition tests: Sinigrin associated with mustard cover crops did not significantly influence the survival of Salmonella (P < 0.05); however plant slurries from mustard significantly reduced Salmonella populations by 1.5 log CFU/ml when compared to other cover crops (P < 0.05). Field Trials: Time to non-detection of Salmonella varied between soil types (clay: 22 days, loam: 52 days) (P < 0.05). No significant decrease of Salmonella was observed after tilling spinach and leaving the field fallow for 15 days. Salmonella was not detected after growing a cover crop, solarization (1 month) and dry-wet events (3 cycles).
Significance: Development of sustainable bio-mitigation strategies to remediate soils contaminated with Salmonella will minimize delays in the accessibility of arable land for safe production of fresh produce.