Comparison of copper levels in runoff from fresh-market vegetable production using polyethylene mulch or a vegetable mulch

Runoff from tomato (Lycopersicon esculentum Mill.) production with polyethylene mulch has been implicated in the failure of commercial shellfish farms in the Mid-Atlantic Region of the United States. Copper, applied in the form of copper hydroxide, is the most widely used fungicide-bactericide for control of tomato diseases and recently has been detected in the Chesapeake Bay (USA) watershed. Elevated levels of copper have been shown to have adverse effects on shellfish, finfish, and other aquatic organisms. This research evaluates the off-site movement of copper with the dissolved phase and the particulate phaseof runoff from controlled field plots containing tomato plants grownin either polyethylene mulch or a vegetative mulch, hairy vetch (Vicia villosa Roth.). Overall, runoff collected from polyethylene mulch plots contained significantly (p <0.05) greater loads of dissolved- and particulate-phase copper than runoff from hairy vetch mulch plots.However, the loss of copper associated with the particulate phase was significantly greater (p <0.05) than that associated with the dissolved phase of runoff from both mulch treatments, with the particulatephase accounting for more than 80% of the copper loads. The reportedtoxicity of copper to aquatic organisms and the greater runoff volume, soil loss, and off-site loading of copper measured in runoff from the polyethylene mulch suggests that this management practice is lesssustainable and may have a more harmful impact on aquatic ecosystems. [ABSTRACT FROM AUTHOR]