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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