Agriculture: Will the yield keep growing?

  • Article by: MATT MCKINNEY , Star Tribune
  • Updated: June 3, 2009 - 10:44 AM

Corn yields seem to rise every year, along with demand. But the question is whether, even with genetic tinkering, the yields will continue to increase.

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Jeff Coulter University of Minnesota extension agronomist, takes a test ride on a research precision planter at the University's farm fields in St. Paul.

Photo: David Joles, Star Tribune

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As farmers put the state's 2009 corn crop into the ground this month, they expect to grow more corn per acre than last year. And if history is any guide, they will.

Farmers today harvest more corn than their parents did a generation ago from the same fields, a fact made evident in historical charts that show corn yield over the past several decades as a steadily rising line.

So reliable is corn's growth of about 2 extra bushels per acre per year that government analysts folded it into their forecasts for this year's 12.1 billion bushel crop. It's just expected.

And yet it's still not enough. The state's ubiquitous crop that's become a staple for feed, fuel, sugar and everything from drywall to shoe polish is in more demand than ever, with a third of the crop going to ethanol.

Some say farmers will rise to the challenge, that corn yields will grow even faster in years to come.

"We are projected to double corn yields in this nation in the next 20 years," said Jeff Broin, CEO of ethanol refiner Poet, a South Dakota-based company that produces 1 billion gallons of ethanol a year.

The reason for at least some of his optimism came last year when scientists cracked the corn genome, a string of 2.5 billion pairs of DNA bases, ushering in the promise of yet more genetic modification of a plant that since 1996 has become one of the world's largest transgenic crops. Seed companies are among those who, like Broin, predict a doubling of corn yields within a few decades.

But the history and hype surrounding corn yields has one staggering asterisk: The very best farms, blessed with the best weather and land, have posted the same yields for at least 20 years -- suggesting they have reached the limit of what the corn plant can produce.

"The odds, if we keep the status quo, of those yield trends slowing down is very high," said Roger Elmore, an Iowa State University professor of agronomy.

Feeding the world

Ethanol producers aren't the only ones banking on more corn. U.S. corn exports will rise 9 percent this year to help feed the world's growing population. Beyond food and fuel, corn also provides building blocks for a wide array of industrial products -- from plastics and foams engineered by Cargill to drywall, shoe polish and firecrackers. For all those reasons, the United States will consume 3 percent more corn this year than it did last year, according to the latest estimates from the U.S. Department of Agriculture.

How long farmers can continue to produce more corn on the same amount of land remains an ongoing experiment, but each year farmers eager to compare notes compete in a contest sponsored by the National Corn Growers Association.

Last year's winner, a farmer in Texas, grew 368 bushels of corn per acre. (In Minnesota, a farmer in St. Cloud grew 272 bushels per acre to win the state competition. The state's late spring makes it less likely that a Minnesota farmer would ever win the national contest.)

The Texas farmer's crop was more than double this year's forecast national average of 155 bushels per acre, but it's roughly the same amount that contest winners have grown since the mid-1980s.

That's why scientists such as Elmore remain skeptical.

"The guys that are making 350 to 380 [bushels per acre], why aren't they making 450 to 480?" he said. "That's the frontier we need to work on."

A history of tinkering

From its earliest beginnings as one of a family of tall grasses grown in Mexico and Central America, corn has held up to human tinkering. Patient cross-breeding over thousands of years turned teosinte, a species of tall grass, into today's maize, as early farmers sought to grow plants with larger ears and more kernels.

As the genetic understanding of corn developed in the 1930s and 1940s, scientist Barbara McClintock produced the first genetic map for corn. That work laid the foundation for modern DNA analysis which, beginning in 1996, produced the first genetically modified corn seed, one that produced a toxin fatal to the corn borer worm, an age-old pest.

Today, the business of selling genetically modified corn seeds is booming as companies unveil new seeds that fight insects, survive on less water and in poorer soils and withstand stronger herbicides. Yet for all of the defenses the transgenic seeds create, none has dramatically increased yields.

"Despite a lot of efforts, there have been no genes of any kind that have increased the yield potential of these crops," said Doug Gurian-Sherman, a senior scientist at the Union of Concerned Scientists and author of a report out last month that doubts the pro-genetically-modified claims of seed companies.

The problem with gene research has been that introduction of a new gene often creates unintended consequences, said Gurian-Sherman, pointing to an example where a gene that looked promising for drought tolerance turned out to make the plant more susceptible to disease. "We shouldn't really hold our breath that the technology is going to do a lot," he said.

Yet hopes have run high since, as a result of ongoing work unveiled last year at Washington University in St. Louis, where scientists said they were close to mapping the corn genome -- a string of 2.5 billion characters that represent the genome's double helix. The work took three years and about $30 million in federal funding. It's only the second cereal crop sequenced; rice, in 2005, was the first.

True believers such as Gerald Tumbleson, a Martin County farmer and former president of the National Corn Growers Association, say research on the corn genome will make the plant a key piece of a new economy to replace petroleum. "We're just beginning to exploit the carbohydrate economy," he said.

Working the land

Scientific controversies aside, farmers say they'll get more corn from something much simpler: precise farming.

"We are farming the land better," said Randall Thalmann, a corn farmer who farms west of Eden Prairie.

Even the seed companies resist the idea that a seed alone can boost yields. It's about the management of the land, said Roy Luedtke, research director at the Marshall, Minn., office of Pioneer Hi-Bred. The company creates a GPS map of farmer's land and then helps match the best seeds to each acre.

And the traditional factors in corn yield -- rainfall, temperature, planting date and frost -- still play a major role.

"A big driver for corn is planting date, and that's determined by weather more than anything," said Jeff Coulter, an extension agronomist with the University of Minnesota.

Earlier planting dates have accounted for as much as 53 percent of the yield gains found in the northern Corn Belt, a study found last year. New seeds that can withstand cooler, wetter conditions allow farmers to plant earlier, adding about two weeks to the Iowa corn growing season since the late 1970s, for example.

The search for a 'yield gene'

Still, it's early in the history of genome mapping. The corn genome contains 55,000 to 60,000 genes. A "yield gene," if such a thing exists, could add 25 percent to farmer's harvests, said Iowa State professor Elmore.

"Yield is a very complex trait," he said. "A single gene is probably not the answer. We've learned that over time, if you look at the yield increases we have seen, it's been from a multiple of things."

His forecast says farmers are more likely to slowly add more corn to their harvests, climbing toward a national average of 280 to 300 bushels per acre by the middle of the 21st century.

"It's just mathematical, and that will take another 40 to 50 years to happen at current trends," he said.

Matt McKinney • 612-673-7329

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