Tech researcher finds way to grow plants on copper-poisoned soils

If there's one thing that the Copper Country has, even after generations of mining, it's copper, and copper-laced soils.

Usually, that's an attribute that is valued for its ability to deter growth of bacteria, mold, and plants; you use soil or additives with copper in them when you don't want things to grow.

But a Michigan Technological University researcher thought way outside that box, and came up with a method to get plants and bacteria to grow in coppery soils, even at the high copper levels found in the Keweenaw.

Biological sciences professor Ramakrishna Wusirika and his research team went to the source for the beginnings of their research: Nature. Torch Lake near Houghton was used as a mine-waste dump during the region's copper-mining boom, but has slowly recovered over the decades to something habitable--and in the process, bacteria have evolved in Torch Lake that tolerate copper quite well. Wusirikia says his theory was that enriching copper-poisoned soils with these bacteria would help plants grow in it.

"We found bacteria that are resistant to high levels of copper," he says. "We thought we might be able to use them to help plants grow better on contaminated soils."

So, they added copper and the copper-resistant bacteria to soil samples, and planted corn and sunflower seeds. They compared those to seeds planted in copper-free soil, and seeds planted in coppery soil without the bacteria.

The copper-free seeds thrived. The copper-soil seeds were stunted, as you might expect. But, his theory was proven correct. The bacteria-enriched coppery soil seedlings did much better than those without the bacteria; almost as well as the copper-free seeds.

"The bacteria seem to help with plant growth, and they also help maize and sunflower uptake copper," says Wusirika.

That means, over time, crops planted on copper-tainted soils, with these bacteria, could actually clean the copper out of the soil. The next step is larger scale testing, as they will apply this method to copper-mining waste soils near Gay in the Copper Country, where hundreds of acres are desolate as a result of the metal content.

Writer: Sam Eggleston
Source: Ramakrishna Wusirika, Michigan Technological University