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Sustainable Agriculture

Cover Crops Deter Root-Damaging Nematodes in Vegetable Systems

When Maryland growers added potatoes to their standard cropping rotations, they discovered a curious, unwanted result. Following potatoes with soybeans, a major commodity grown on Maryland's Eastern Shore, they experienced more problems with crop-damaging nematodes than ever before.

They approached their Dorchester County extension agent, who connected them with University of Maryland scientists, who began Sustainable Agriculture Research and Education-funded research into nematode control methods. The researchers focused on the troublesome root knot nematode that was affecting local yields.

“The growers didn't want to give up potatoes as a crop because potatoes fit well in their rotation, but they wanted to know what they could do, culturally, to reduce nematode levels,” said Kate Everts, a University of Maryland plant pathologist and project leader. “They were having problems they had never had before.”

The treatments, co-designed and tested by area farmers and at a research station, focused on planting cover crops and adding organic soil amendments. Everts found that planting 2 years of a summer cover crop—sorghum sudangrass—combined with poultry litter soil amendments was effective in stemming nematode populations.

The “winning” rotation: a winter small grain, followed by potatoes or cucumbers, then a summer cover, and back to a small grain. After 2 years, farmers planted soybeans following the spring potatoes. In that third year, researchers saw a reduction in nematodes, followed by improvements to soybean yields.

When extension specialist and collaborator Bob Kratochvil tested similar treatments, the sorghum sudangrass also worked to cut the nematodes' presence in the soil.

“If you interrupt a host species with a nonhost species, you diminish the population so they're more manageable,” he said.

At least one farmer plans to continue planting summer cover crops to deter the pest.

“It's learning in progress, and we're still experimenting with cover crops,” said David Andrews, who farms 2,600 acres in Dorchester County. “We've noticed a difference in the nematode populations—not 100 percent reduction, but we're getting there.”


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