Organochlorine residues from past agricultural practices continue to pose problems for Oregon’s growers. Even trace residues can affect produce grown on contaminated soils. Oregon Tilth undertook a two-year survey of plant uptake under field conditions with trace OC residues. While few crops showed uptake levels exceeding federal limits, many surpassed organic standards for contaminant content. Rates of uptake varied significantly within and among the crops tested. Uptake rates varied depending on the amount and type of contaminant present. Test results also varied within a given sample. Still, certain plants show a tendency to absorb contaminants, while others appear safe to grow on soils with trace levels of OC contamination.

This experiment demonstrates that carrots and squash are at-risk crops for ground contaminated with chlordane. Carrots, cucumbers, melons, and squash are shown to be at-risk crops for ground contaminated with dieldrin. Beans, broccoli, corn, lettuce, tomatoes, and peas appear low risk for ground contaminated with chlordane, dieldrin, or DDT.