Ames, Iowa
July 9, 2008
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Currently, living
mulch negatively impacts yield. The corn on the
left is not competing with ground cover. The
corn on the right, which has living mulch
between the rows, must compete for water and
nutrients. Once researchers find the right
combination of corn and ground cover, they
believe yields will not be impacted, and soil
quality will be maintained. |
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Ground cover may be one workable
method to reduce the effects of erosion that future biomass
harvests are predicted to bring.
Iowa State University
researchers are looking at ways to use ground cover, a living
grass planted between the rows of corn, in production farming.
The seemingly limitless national appetite for ethanol has
industry and government looking beyond the kernel to the entire
corn plant for more fuel.
But corn, the source of most of the United States' ethanol, is
not limitless, so turning corn stalks and leaves into ethanol is
the target of much research.
The U.S. Department of Agriculture projects that by the year
2030, about 20 percent of ethanol will be made by turning corn
stalks and leaves, known as corn stover, into fuel. That
projection assumes that 75 percent of this corn stover can be
harvested for biofuels. Currently, stover is not used to make
ethanol.
Farmers now leave corn stover on their corn fields to slow wind
and water erosion and re-supply the soil with organic material
to ensure future productivity.
"The issue is this," said Ken Moore, Iowa State University
agronomy professor. "How do you harvest corn stover in a way
that sustains the productivity of the environment for producing
future corn?"
Just as important as the loss of soil through erosion is the
loss of organic material that the removal of the stover would
bring.
On an average acre of Iowa farmland, there are roughly four tons
of stover. Under the expectations laid out by the USDA, three of
those tons would be removed and processed into ethanol. That
organic matter that won't be returned to the soil to help future
crops grow.
"We know that soil organic matter is critical," said Jeremy
Singer of the USDA's National Soil Tilth Laboratory in Ames.
"And removing that stover over time is going to decrease the
amount of organic matter in the soil. That will lower
productivity."
To combat the coming problem, researchers are looking into ways
to lower soil erosion while retaining vital organic materials.
"This is a real educational moment," said Singer. "If farmers
are going to harvest stover, they have to replace the carbon in
the soil."
One promising solution is the idea of planting a ground cover
grass between the rows of corn that remains year-round. This
grass would not be harvested.
This ground cover, or living mulch, will perform all the
functions that corn stover currently does.
"Imagine," says Moore, "a large flat golf course where you've
gone through with a tillage instrument and you've tilled-up
every 15 inches. That's what it would look like in farmers'
fields."
"The value you get for the production system is that you could
harvest as much of the corn stover as you want without having
any problems with conservation," said Moore.
"There is a lot of ecological sense to this."
The challenges that the researchers are studying include finding
which types of grass will not compete with the corn, what type
of corn will withstand the competition, and what sort of
agronomic practices will work best.
"Corn is not a very competitive species particularly early in
the season," said Kendall Lamkey, professor and chair of Iowa
State University's agronomy department. "Corn doesn't like to be
growing with anything else in the field."
But later in the growing season, corn can be a little more
hospitable to having neighbors share its space.
By the time the corn plant is five inches tall, the kernel
number on the corn plant is already determined. That is a
measure of the plant's potential yield, said Lamkey.
Stress early in the growing season can affect yield greatly, he
said.
While this research has just begun, Moore says that this idea is
not new.
"Nature does this all the time," he said. "You see prairies that
have these complementary mixtures of multiple species that grow
and share space. In a way we are sort of simulating the
grassland systems that were originally here, but in very simple
way."
The grass between the rows will also have other advantages in
addition to the ecological benefits.
Grasses will help keep weeds down. This will reduce the need for
herbicides. Also, grasses, combined with some types of fungi,
will help reduce the number of insects that require farmers to
spray, said Moore.
These ground cover grasses can also be selected for any number
of traits, just like corn can be, said Moore.
"We are trying to identify the right system of herbicide, strip
tillage, and species combination that minimizes competition with
corn and maximizes benefits," said Singer.
The one obstacle that researchers must overcome is the effect on
corn yield.
In the current stages of the research, corn yield suffers
because of the competition from the ground cover grasses, said
Moore.
"Our goal is produce a ground cover that will not interfere or
compete with corn production in any way," he said.
Once that problem is solved, the researchers say that using
living mulch as ground cover will be an ecologically sound
method of keeping a nutrient-rich soil while harvesting stover
in the amounts that the USDA predicts.
"I think by the end of the project in two or three more years, I
am optimistic that we'll be able to identify the one or two
species of grass that we really need to work with for the living
mulch," said Lamkey.
"I am also fairly optimistic that we'll be able to identify
inbred corn lines that do well in these systems," he said.
That day may not be too far into the future, according to Moore.
"I can envision a day," said Moore, "when smart seed companies
are co-developing these packages where they sell ground cover
seed and corn hybrids that work in association." |
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