New Jersey farm soil copper levels resulting from copper fungicide applications

Abstract

Vegetable growers have expressed concerns regarding the accumulation of copper in soil where copper-based fungicides are used and have requested guidance for copper pesticide applications. Elevated soil copper levels have the potential to become toxic to sensitive crops and impact soil health. In response, total and available soil copper levels were surveyed using soil analysis of samples from 15 New Jersey farms representing organic and conventional production methods. Lettuce (Lactuca sativa) was grown in the sampled soil in a greenhouse trial and evaluated for signs of copper toxicity. We found that all 15 farms were using copper fungicide preventative sprays during the previous 2 years. The soil copper levels of these farms were higher in copper-applied soils than the corresponding noncopper-applied soil. Soil copper levels were not near or in excess of established clean-up limits at any of the locations. Greenhouse-grown lettuce in the sampled soils was not negatively impacted by the copper levels. Due to the increase in the total and soluble soil copper levels, growers should use best management practices to prevent the accumulation of excessive amounts of copper in the soil over time.