Test That Soil, Raleigh Gardeners

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Spring planting time has arrived in the Piedmont and Raleigh’s growing community garden scene is swinging back into action for another year. Raleigh recently amended its zoning laws to allow community gardens to take up an entire property, and the city is considering ways to make vacant city-owned property available for gardens.

As more Raleigh residents get engaged with community gardens and more pop up around the city, would-be gardeners need to make sure they aren’t growing food on contaminated soil.

The Wedge Garden off Hillsborough Street just west of downtown.

All gardeners benefit from standard soil tests, which are available free-of-charge through the North Carolina Department and Agriculture & Consumer Services and will tell gardeners what kind of nutrients they need to add to the soil for a successful season. Urban gardeners may need to take special care if they do not know the plot’s previous uses. Commercial or private uses can still leave behind soil pollutants from chemicals, pesticides or even just a car dripping oil onto the dirt over time.

Some signs that soil pollutants may be present include lack of vegetation or discolored vegetation, soil that smells funny or looks different from the soil around it.

Mark Powers, regional supervisor with the state’s Underground Storage Tank program, suggested using your nose, too.

“The sniff test is the best,” he said. “If you are only talking about 5 gallon buckets’ worth of petroleum-scented soil, like a parked car was dripping over time, you can put it in your garbage.”

If the amount of affected soil measures more than five gallons, but is manageable, scoop it up and take it to the nearest facility that manages petroleum-laced soil. If the whole lot is affected, regardless of the pollutant, be sure to report it to the property owner or, if it is public land, to the city.


Managers at Spanish Terace Apartments say tenants were pleased when they filled in the pool, built a courtyard and added a garden.

Powers also cautions everyone to use common sense.

“It could be dangerous if somebody comes across leftovers from illegally dumped nonpetroleum chemicals – especially leftovers from making methamphetamine. It’s a good idea to wear gloves while dealing with the spill and wash your hands afterwards.”

Petroleum is only one potential soil pollutant. Heavy metals exist naturally in soil, but excess levels can come from a variety of sources. Heavy metal soil tests check for excess arsenic, cadmium, chromium, copper, lead, mercury, molybdenum, nickel, silver, selenium and zinc, but they are not free. Enco, Microbac and Element One are three area labs that perform the tests, but other facilities exist.

So long as the soil is not noxious vapors, even polluted plots can be used safely for food crops by not planting directly into the soil. “Using a raised bed, it would be your safest bet, “said Tony Duque, hydrogeologist and Brownfield project manager with the state. “You basically want to keep the roots out of the soil so the height of the bed will vary per plant.”

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