I won't throw water on the dream of 300-bu. average corn yields. And yes, long-term yield trends are going in the right direction, even with this crazy year, when a big percent of the crop won't be harvested before November.

But shooting for 300-bu. average corn is at best a long-term goal that will require much more dramatic tech breakthroughs – and perhaps dramatic changes in weather patterns - than the economic and agronomic conditions we have today.

The truth is, yields are still tied to the vagaries of weather, economics, efficient use of inputs and excellent management. Technology alone won't break the 300-bu. mark.

Historically, our higher yields have probably been more a function of good weather than technology, says University of Illinois agronomist Emerson Nafziger. "We are dodging bullets," he says. "The reason we dodged bullets in '08 and again possibly in '09, from some sketchy weather, is that the hybrids allowed us to do that."

If 300 bu. corn becomes commonplace, will every field be managed like contest fields? If not, what do current data suggest with regards to inputs? What will fields look like in 2030?

Water, the limiting factor As a C4 grass, corn is relatively efficient in its use of water to produce dry matter. However, water is still a barrier to 300-bu. average yields, notes Nafziger.

In the Corn Belt, 200-bu. corn requires 22 inches of water; if crop efficiency stays constant, 300-bu. yields will need about 33 inches of available water. Soil water storage and seasonal rainfall is less than 30 inches across most of the Corn Belt, most of the time.

Most of the topsoil-rich Central Illinois soils can hold 10 to 12 inches of water for the crop; in many other parts of the Corn Belt it’s probably half of that. So where will the water come from? Will irrigation become commonplace? Is it sustainable, considering the growing water shortages we face around the world?

In Western Illinois last year, the NCGA contest winner for Class AA (non-irrigated) corn averaged 348 bushels per acre. “It never stopped raining,” said Mark Dempsey, the Fowler, Ill. farmer with the winning plot.

Soil's 'sweet spot' Yield contest numbers tend to get people's blood pumping. But they are not a realistic indicator of things to come, at least as far as yield trends go. That no single input or rate needs to demonstrate its contribution to yield in a yield contest. You’re there to win a contest, not fix your margins. If they are anything, contest winning yields are the result of a persistent search for soil's ‘sweet spot,” and a patient wait for ideal weather.

In other words, things have to be just right – both economically and agronomically – to get high yields. Outside of yield contests, how will we ever trend toward 300-bu. corn if input costs discourage high plant populations or optimum nitrogen rates, for example?

Ironically, Nafziger's research shows that high yields do not always need high nitrogen rates, in corn following soybeans. "You don’t need to put on 200 bu. nitrogen to get 200 bu. yields," he says.

In fact, N rate is clearly not the primary determinant of corn yield in highly productive soils. N supplied in soil organic matter and crop growth are both related to temperature and water.

Delicate journey Consider the delicate journey a corn plant must make to achieve contest-winning yields. For one, it must have perfect growing conditions. Second, it must have very little stress. And perhaps most important, it must be planted, in conjunction with its neighboring plants, so as to perform flawlessly by the time harvest rolls around.

"The only way to pursue and achieve higher grain yields on a per-acre basis at high plant densities is to make sure that every single plant has the opportunity to compete with its neighbor in the row," says Purdue agronomy professor Tony Vyn. "The only way to achieve this competition ability is to have the genetic resources, in terms of a hybrid's ability to compete and gain access to nutrients and water."

Vyn and his colleagues recently completed a three-year study looking at individual plants in a field and how they perform. He even bar-coded each of the 4,000 plants when they first emerged from the soil, and examined yield based on plant density and nitrogen levels.

What he discovered is that barren plants or ears with few kernels result mostly from how that plant was able to compete with its neighbor in capturing sunlight, producing a big leaf area, timely silking, and retaining its green leaves well into grain fill.

"There is a season-long, management-dependent, intense competition that occurs among adjacent plants," he says. "Competition is enhanced at high plant densities, especially when nitrogen is limiting."

From an industry standpoint, Vyn says seed companies must study the response of their hybrids and germplasms to higher plant densities in the context of nitrogen use efficiency.

"As we've tried to push yield barriers beyond 300 and 350 bushels per acre, it's extremely important that we think about the ability of the plant to tolerate not just a single stress like high plant density, but also be able to tolerate lower nitrogen availability on a per-plant basis," he says. "Our results suggest that on the plant breeding side of the equation, more attention should be focused on the joint ability of new corn hybrids to tolerate combined stresses of both high plant density and limited nitrogen.

"If the new hybrids can better tolerate both, then it will be possible for those high-density, low-nitrogen situations to achieve an overall improvement in uniformity of grain yield on a per-plant basis."

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