A study on the effects of nitrogen and potassium fertilizer on post-harvest salmonella levels in tomatoes showed the concentration of the fertilizers did not have a measurable effect on susceptibility to the pathogen.

However, the report’s authors said timing of harvest and tomato maturity may play a role.

The study, published at ScienceDirect online, evaluated how field conditions affect post-harvest food safety outcomes.

The research tested how different levels of nitrogen and potassium fertilization affected the presence of salmonella, according to an online summary.

Two tomato varieties werre grown over three seasons under high, medium, and low levels of nitrogen and potassium fertilization in two locations. They were inoculated with seven strains of salmonella, according to the summary.

“Even though the main effects of nitrogen and potassium fertilization on the susceptibility of tomatoes to infections with salmonella enterica were not statistically significant overall, differences in nitrogen concentrations in plant tissues correlated with the susceptibility of partially ripe tomatoes to salmonella,” according to the summary.

The researchers found tomato maturity and the season in which tomatoes were produced had the strongest effect on the ability of salmonella to multiply in tomatoes, according to the summary.