CORVALLIS, ORE. – Lead has been in the spotlight recently as a hazard in imported toys, but it also is a potential hazard in garden soil, experts say. A new publication from the Oregon State University Extension Service tells how to evaluate and reduce lead hazard in gardens and landscapes.
"Very few soils in Oregon have significant lead contamination," explained Sam Angima, OSU Extension natural resources faculty member based in Lincoln County. "If you know about the history of the site, you can get a pretty good idea if lead has been added by human activities."
Soils with the highest risk of lead contamination are in redeveloped industrial areas; adjacent to busy and dusty highways – and deposited before the 1996 ban on leaded gasoline; next to old houses, where lead in paint was highest before 1960 and was banned in 1978; and in old orchard sites. Lead-arsenate was sprayed in orchards from about 1910 to 1950.
If you suspect that your soil might be contaminated with lead, a soil test can be performed by many commercial testing laboratories. The new OSU Extension publication provides general guidelines for interpreting soil lead tests. A list of commercial labs that perform environmental soil tests (including lead) is available at the OSU Extension publication website: http://extension.oregonstate.edu/catalog/details.php?search=EM8677&submit.x=9&submit.y=3
"This information will be especially valuable to people buying property who want to make sure the soil is not lead-contaminated," said Dan Sullivan, Extension soil scientist. "If lead levels are very high in soil, we don’t recommend vegetable gardening. The only way to know if lead really is a problem is to have your soil tested."
The most important thing to remember about reducing lead hazard in the garden is that it’s all about dust, Sullivan said.
"Lead is strongly bound to soil particles and not very soluble in water, so plant roots don’t take up much lead from the soil,” Sullivan pointed out. “If you minimize dust exposure, you minimize lead exposure.
"If the soil does contain high lead levels, you can greatly reduce lead hazard by covering the soil, preventing dust movement,” he added. “Cover lead-contaminated soil with a perennial ground cover, dense turf grass or heavy organic mulch. Or, you can reduce the risk by growing vegetables and flowers in clean soil in raised beds or containers. Peeling and carefully washing produce also reduces risk."
Other soil amendments and fertilization practices can be used to reduce lead uptake by plants. To get the most benefit from soil amendments and fertilization practices, Angima recommends collecting a soil sample and getting a fertilizer recommendation and then follow guidelines suggested in the new publication.
"Soil outside the house is only one avenue for lead exposure," Angima said. "If you suspect lead-related health problems, contact your physician. Your local health department or the Oregon Department of Human Services can assist in determining what lead hazards exist and how to remedy them."
More details are in the OSU Extension publication, "Evaluating and Reducing Lead Hazard in Garden and Landscapes," available at:http://extension.oregonstate.edu/catalog/pdf/ec/ec1616-e.pdf.