Ames, Iowa
February 4, 2004
By Susan Thompson
U.S. corn yields have been increasing steadily in recent years
at a much higher rate than soybean yields. Concern over
aphids, nematodes and diseases that attack soybean fields,
plus the corn yield trends, have led some producers to
consider changing from a corn-soybean rotation to either
continuous corn or two years of corn followed by one year of
soybean.
One benefit of a corn-soybean rotation is it helps control
diseases and pests that bother each crop. "Producers are
really taking a chance if they don't rotate," said Palle
Pedersen, Iowa State
University soybean extension agronomist. "Diseases and
pathogens build up in the soil and rotation helps manage
them."
"Research shows the most profitable rotation in the Corn Belt
is the corn-soybean rotation," he said. "The nitrogen provided
by soybean for growing corn is a major reason for this
profitability."
Pedersen was involved in a 15-year research project at the
University of Wisconsin that studied corn and soybean yields
based on rotation sequence and tillage systems. " First-year
corn and corn rotated annually with soybean yielded higher
than continuous corn," Pedersen said. "In addition, first-year
soybean yields were 12 percent higher than the other six
soybean rotation sequences studied."
Not only do yields increase with a corn-soybean rotation, so
do profits. "In this study, both first-year corn and soybean
produced the highest returns. We concluded that first-year
corn or soybean and alternating corn and soybean were the most
profitable rotation sequences over the last 15 years in
Wisconsin," Pedersen said.
Pedersen believes the same is true in Iowa. But to provide
scientific proof, he has launched a similar research project
at three ISU research farms. Various rotations combined with
two tillage methods - no-tillage and chisel plow - will be
studied in this long-term experiment.
"In Wisconsin, we found that conventional tillage increased
corn yield by an average of 8 percent, but did not affect
soybean yield. We also found producer returns were higher for
corn in a conventional tillage system, but there was no effect
on soybean returns," Pedersen said.
Another benefit of crop rotation is that with different
planting and harvest dates, producers spread out their
workload. "Farming is a business. Producers need to consider
everything, and keep an eye on the bottom line," Pedersen
said.
Pedersen knows
bean prices have been low in recent years. But he thinks the
strong uptrend in new-crop soybean prices, higher anhydrous
fertilizer costs and research that shows the value of a
corn-soybean rotation will help Iowa producers make better
decisions.
Susan
Thompson is a communications specialist with the Iowa State
University College of Agriculture.
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