New University of Idaho research suggests copper concentrations in some sandy-soiled Idaho farm fields treated with dairy lagoon water may be nearing levels that could stymie potato root growth. Most dairies use copper sulfate for foot baths that protect the hooves of cattle from problems such as foot rot.
U of I Extension soils specialist Amber Moore detected stunted potato growth in loam soils beginning at 90 parts per million of copper. In sandy soils, plants were affected at levels as low as 25 parts per million.
Moore acknowledged copper levels generally aren't a problem in Idaho fields but warned "it could take a century to get that copper out of your field to where it's not a problem."
