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Narrow Rows Can Help Curb Waterhemp

Feeling
whipped by waterhemp? Well, you’re in good company. While many of you had
scorched soybeans from this summer’s drought, waterhemp fared just fine.

There’s
one tool to keep in mind, though, that can help you contain this monster weed:
Narrow rows. Bob Hartzler, Iowa State University Extension weeds specialist,
discussed this tool at this week’s Bayer CropScience Respect the Rotation tour
near Ellsworth, Iowa.

Soybeans
planted in 15-inch rows canopy quicker than soybeans planted in wider rows.
“Narrow rows have almost the same benefit as a mid-season cultivation,” says
Hartzler.

Narrow
rows block sunlight from reaching weed seeds. With no sunlight, weed seeds
can’t germinate. Thus, narrow rows can help nix late-season waterhemp surges.

“Waterhemp
that escapes later in the season might not impact yields, but it produces lots
of seed that causes problems in future years.”

White
mold is one drawback to narrow rows. Bear in mind, though, that white mold
doesn’t always cause a problem every year. A field infested with waterhemp
does.

“I
don’t want to belittle diseases, but waterhemp poses a greater threat to
profitability than white mold,” says Hartzler.  

Other
cultural weed management tools like preventing seed movement between fields and
managing weeds in field borders will increase in importance, says Hartzler. In
the Midwest, even farmers who rotate corn and soybeans gain little diversity from
a weed management viewpoint.

“We
are planting two summer crops, with nearly identical planting and harvesting
dates,” he says. “We are using similar weed control tactics in both crops. The
whole system is set up for large acres and as little as labor as possible. Cultural
practices are something that need to be looked at more closely.”

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