Madison, Wisconsin
February 27, 2008
U.S. farmers plant corn much
earlier today than ever before and it seems to be paying off, at
least in the north. Earlier plantings could account for up to
half of the yield gains seen in some parts of the northern Corn
Belt since the late 1970s, a new study has found.
Midwest corn-growers produce three times more corn today than
they did a half-century ago. After finding that farmers also sow
seeds around two weeks earlier now than 30 years ago, Chris
Kucharik, a scientist with the
University of Wisconsin-Madison Nelson Institute for
Environmental Studies, set out to discover if earlier plantings
– and, thus, longer growing seasons – have contributed to the
jump in production.
In a study published online today (Feb. 27) in the
Agronomy Journal,
Kucharik reports that earlier planting could help explain 20 to
50 percent of the yield gains in the northern Corn Belt states
of Nebraska, South Dakota, Minnesota, Iowa, Wisconsin and
Michigan since 1979. Meanwhile, the other major factor he
considered, climate, seems to have had little impact.
“What I found was that while climate probably has contributed in
a small way to the yield trend, the overwhelming contribution
has been from this land management change,” says Kucharik, an
expert on climate and agriculture with the Nelson Institute’s
Center for Sustainability and the Global Environment (SAGE).
As concerns about climate change continue to rise, scientists
are struggling to forecast the potential impacts – both positive
and negative – on the world’s ability to grow staple crops like
corn. This is especially true now, as corn is being increasingly
tapped as a feedstock for ethanol production.
While the focus on climate is warranted, Kucharik cautions that
scientists can’t lose sight of the role of human decision-making
and management practices. His study reveals that farmers aren’t
necessarily planting their crops sooner because of warmer
springtime temperatures brought on by global warming. Instead,
seeds engineered to endure the colder and wetter soils of early
spring have likely allowed northern farmers to adopt
longer-season – and higher-yield – hybrids.
“Before we jump to conclusions about the impacts of climate
change on agriculture, we really need to consider subtle
management changes that are taking place and will likely
continue to take place in the future,” says Kucharik. “Anytime
you deal with a system that’s being managed by people, it makes
for a more complicated story.”
Besides climate, researchers have most often attributed
skyrocketing yields to technological advances, including
mechanization, better crop genetics and pesticides and
fertilizers. But after finding in a previous study of U.S.
Department of Agriculture data that Midwest farmers put corn
into the ground much earlier now, Kucharik began pondering the
possible impact of this unexpected shift.
“I thought, if farmers are planting earlier, that means they’re
extending the growth period of crops – the amount of time plants
have to be photosynthesizing, piling on biomass and making
grain,” Kucharik says. “So it made sense to me that this would
have contributed in some way to the yield gains we’ve seen over
past decades.”
His hypothesis turns out to be true – in part. In Iowa, for
example, earlier planting dates and longer growing seasons have
potentially contributed 53 percent of the statewide yield gains
over the past 30 years, Kucharik found. In Wisconsin, that
number is 22 percent, and it ranges between 19 to 31 percent in
other northern states.
Yet, even though southern Corn Belt states sow seeds even sooner
than their more northerly neighbors, Kucharik saw no
relationship in Illinois, Indiana, Kansas, Kentucky, Missouri
and Ohio between planting dates and yield.
“There was definitely a split – not all of the states showed
this relationship,” says Kucharik. “But for the ones that did,
it made sense that they were the ones more likely to benefit
from an extension of the growing season” and a switch to
longer-season hybrids.
He explains that because southern farmers have been planting
long-season, high-yield corn hybrids for decades, expanding the
growing season by another two weeks likely offers little
advantage. Shorter growing seasons in the north, on the other
hand, have historically limited farmers there to short- or
mid-season hybrids that produce less grain.
Whether the trend toward earlier planting can continue is
another matter, says Kucharik. Northern farmers will eventually
hit up against frozen ground and other wintry conditions that
will be impossible to overcome.
“Especially as we’re going through this transition of using corn
as the initial feedstock for biofuels, are we thinking that this
trend in yields is going to continue indefinitely"” he asks. “If
planting earlier does contribute significantly in some regions,
eventually that effect will wear itself out.” |
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