Investigating Metrics Proposed to Prevent the Harvest of Leafy Green Crops Contaminated by Floodwater

Abstract

Pathogens can be transported by water through soil to contaminate distant crops. The California LGMA states that leafy green crops within 30ft of flooded soil should be destroyed due to potential contamination. Previously flooded areas should not be replanted for 60 days. This study investigated the transport of Salmonella enterica and Citrobacter freundii through soil in a model system with a positive slope (uphill). Field trials involving flooding one end of a spinach bed with a negative slope (downhill) with water containing Escherichia coli were also conducted. Soil type, soil moisture content, and slope affected bacterial movement. In field trials, E. coli was quickly transported to the 30ft boundary, and persisted significantly longer in the fall trial than the spring. These data suggest the LGMA metrics need to provide additional parameters to prevent the harvest of leafy green crops potentially contaminated by floodwater.