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Pushing the Yield Limits
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Six-thousand-gallon water tanks are
used to simulate farm ponds in the
recirculating subirrigation/drainage
system.
(K9472-1)
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In an era of little
interest in maximum yields—when the very topic seems politically
incorrect—Dick Cooper is talking about maximum soybean yields that few can
even imagine.
Cooper can talk yields of 100 bushels per acre for soybeans because for the
past 24 years he's devoted an acre of land—divided into test plots—to
finding the maximum yields possible with soybeans. For these experiments, he
isn't concerned with what's practical or economic; he just uses these plots to
check on what's possible. Cooper is in the ARS Corn and Soybean Research Unit in
Wooster, Ohio.
To get the type of yields only seen occasionally by farmers who win local yield
contests, Cooper removes all manageable yield-limiting factors. He gives his
plants all the water and fertilizer they need, which might not always be
economically feasible in commercial farming. But many of the practices he uses
can be—and in some cases have been—adopted by farmers. Practices such
as early planting and using semidwarf soybean varieties. |
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In Wooster, Ohio, technician
Tim Mendiola measures plant
height of semidwarf varieties
grown in the maximum yield
studies.
(K9471-1)
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Certainly, practicality
is Cooper's bottom line. From that 24-years-and-still-going experiment, he has
recently identified a "photothermal barrier" to higher soybean
yields. The photothermal barrier theory is that a warm spring season will
trigger earlier flowering, resulting in higher yields.
"This brings on the reproductive stage at a time of year when light
intensity is greater and the days are longer, extending the length of the
reproductive cycle," Cooper says. The theory can be put to practical use
by developing full-season soybean varieties with earlier flowering. But until
that happens, farmers have to settle for earlier planting.
Cooper also used the maximum yield experiment results to develop a practical
system called High Yield System in Place, or HYSIP. HYSIP involves early
planting of ARS-developed semidwarf soybean varieties in densely seeded, narrow
rows every year. This takes advantage of the ability of the solid-seeded
semidwarf soybean system to yield exceptionally high in years with favorable
rainfall. He recommends that farmers use semidwarf soybean varieties on
productive soils. The first such variety, Elf, was released from Cooper's
program in 1977. Subsequently, many new varieties have been released from his
program, the most recent being Stout and Strong. |
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Soybean breeder and production
specialist Richard Cooper (left)
and soil scientist and water
management specialist Norman
Fausey have pooled their
expertise to develop a
subirrigation/drainage, crop
management system that
consistently provides soybean
yields of 70 or more bushels per
acre and corn yields of 200 or
more bushels per acre.
(K9473-1)
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Cooper recommends
planting the crop between May 1 and 15 in his area, instead of the usual May
15–30, and farmers are doing this.
"We recommend that farmers plant seeds in rows 7 inches apart, instead of
the traditional 30-inch row spacing," he says. "Seeds should be
planted at a rate of 300,000 per acre for semidwarf varieties. On poorer soils,
we recommend staying with traditional varieties, at a rate of 225,000 seeds per
acre."
Pipes To Irrigate and Drain
Cooper has merged HYSIP with a subirrigation/drainage system developed at Ohio
State University (OSU) in Columbus, Ohio, by ARS soil scientist Norman R.
Fausey. Cooper says the idea of merging his and Fausey's systems came when he
heard Fausey speak at a 1984 water-management meeting. "This is the first
project to merge maximum-yield trials with irrigation-management
experiments," Cooper says.
"At the time of that meeting," says Fausey, "people thought of
poorly drained areas in terms of having too much water. Spring flooding and
soils too wet for planting stood out in their minds. But my research experience
showed me another side to the problem: In most years we have yield losses due
to not enough water later in the summer. I conceived the idea of saving some of
that extra water from spring for use when water gets short in summer."
The irrigation system pumps water into underground drainage pipes during the
hottest, driest part of the summer. The idea of irrigating through drainage
pipes is to keep the water table constant, so plants never experience drought.
Just a few days of drought at critical times in a crop's development can reduce
the true yield potential.
The system has now evolved to include recycling irrigation and drainage water.
The goal is to develop a system where farmers' drainage water would empty out
into a wetland, which would filter out nitrogen and phosphorus. The water would
then be stored in a pond or reservoir and later reused to irrigate through the
same underground drainage pipes.
To substitute for the ponds, reservoirs, and wetlands in the experiments,
Cooper and his colleagues use eighteen 6,000-gallon tanks to store the water
for reuse. Cooper works with OSU and Fausey on this. Normally, the drainage
water from the underground pipes empties directly into nearby streams,
potentially bringing with it excess nitrogen and phosphorus, as well as
pesticides. Preliminary data indicate that the recycled water is significantly
cleaner than water emptied directly into streams.
Because of the water quality improvement potential and the value of wetlands,
ponds, and reservoirs to wildlife, the U.S. Environmental Protection Agency and
the Lake Erie Environmental Protection Fund have been funding three large-scale
demonstrations of the recycling water experiment in the Toledo, Ohio,
area—near Lake Erie. The funding for the demonstrations was obtained under
the leadership of Bernie Czartoski, coordinator of the Maumee Valley Resource,
Conservation and Development Council, with collaborators from ARS, Ohio State
University Extension, USDA's Natural Resources Conservation Service, and
industry.
"We built wetlands and reservoirs to store and recycle water to irrigate
corn and soybean fields that are from 7 to 30 acres," Fausey says.
"We're seeing an increase in wildlife numbers and diversity at these
wetlands and reservoirs—everything from deer and raccoons to birds and
frogs, including an increase in numbers of Blanchard cricket frogs, which were
thought to be endangered."
The subirrigation/drainage system is not widely used yet because of costs, but
Cooper is optimistic it will spread. It requires that drainage pipes be spaced
half the usual distance apart, to allow irrigation water to reach midway
between pipes, covering all the land. "Because of the improvement in water
quality from recycling, the possibility of government subsidy to help cover
installation costs could be a significant factor in grower adoption,"
Cooper says.
"The irrigation stabilizes yields, so farmers in a dry year would have
higher yields than they normally would, at a time when prices are high because
of drought. It works best for poorly drained soils that are reasonably level,
which perfectly describes much of northeast Indiana and northwest Ohio,"
Cooper says. "And HYSIP puts farmers in a good position to have high
yields when there is enough rain. It won't happen every year, but the system
gives farmers the potential to have high yields when conditions are right,
resulting in higher long-term average yields," he says.
Over his 10-year experiment with HYSIP, Cooper found that without irrigation,
there was a substantial yield advantage of 24 percent over the standard system.
"The merged systems—HYSIP and subirrigation/drainage—promise
consistent annual yields of 70 to 80 bushels per acre for soybeans and 200-plus
bushels per acre for corn," Cooper says. "In years with a warm early
spring, the experiments have yielded 90 to 100 bushels per acre for
soybeans."
"These results demonstrate the value of long-term high yield research.
Without the long-term data and the removal of other yield-limiting factors, it
is doubtful the delayed flowering barrier to higher soybean yields under normal
spring temperatures would have been identified.
"As a result of this new knowledge, I anticipate a major effort will be
made by soybean breeders to select for earlier flowering," Cooper
says.—By Don
Comis, Agricultural Research Service Information Staff.
This research is part of Water Quality and Management, an ARS National
Program (#201) described on the World Wide Web at
http://www.nps.ars.usda.gov.
Richard L. Cooper is in the USDA-ARS
Corn and Soybean Research Unit at the
Ohio Agricultural Research and
Development Center, 1680 Madison Ave., Wooster, OH 44691-4096; phone (330)
263-3875, fax (330) 263-3887.
Norman R. Fausey is in the USDA-ARS
Soil Drainage Research
Unit at The Ohio State University, 590 Woody Hayes Drive, Columbus, OH
43210-1058; phone (614) 292-9806, fax (614) 292-9448. |
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"Pushing the Yield Limits" was published
in the June
2001 issue of Agricultural Research magazine.
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