URBANA, Ill. — Results of a study completed by the Illinois Crop Physiology Laboratory, led by University of Illinois physiologist Fred Below, seem to prove corn yield gaps – described as the difference between a farmer’s actual yield and the potential yield for a field – can be reduced by a systematic approach to the problem.

The study, which used combinations of five management factors in corn-following-soybean trials, indicated corn yields in Illinois can be increased by about 28 percent using commercially available technologies and hybrids. "We know we have to increase our corn production to meet the needs of a growing population and a greater demand for animal products. Parts of the world that are becoming more prosperous are demanding more animal protein, which means more corn," said Dr. Laura Gentry.

She is director of water quality research for the Illinois Corn Growers Assoc. and adjunct for the Natural Resources and Environmental Sciences Department with the U of I Department of Crop Sciences. "We know we need to increase our corn production, but on the same amount of land. There had been several studies stating this, but none that had asked, ‘How do we do it?’"

The study’s authors – Below, Gentry, statistician Natias Ruffo, graduate student assistant Adam S. Henninger and Juliann R, Seebauer – employed an "addition/omission" study design which entailed applying each of the five management factors (plant population, transgenic trait, fungicide, nitrogen fertility and phosphorous-sulfur-zinc fertility) at both traditional and advanced levels.

"We wanted to see what would happen when you use a traditional versus an advanced management approach that encompassed a wide variety of agronomic practices," Gentry explained, adding "omission treatments" were created by applying a single factor at the traditional level while maintaining all other factors at the high-tech level.

"Addition" treatments were also created by applying a single factor at the advanced level while maintaining all other factors at the lower level. The two-tiered approach allowed the research team to monitor two important control techniques and determine the most effective practices for narrowing the yield gap. The researchers concluded a "systems approach" involving an intensified management system that included increased plant population, transgenic (Bt trait) insect resistance, strobilurin-containing fungicide, balanced crop nutrition (phosphorous-sulfur-zinc) and supplemental sidedressed nitrogen can produce a yield increase of 28 percent more corn grain compared to a standard management system.

More importantly, Gentry noted no single factor or technology accounted for the yield increase the researchers observed. Rather, they credited the yield jump to a "greater-than-additive effect" of factors working together. In addition to studying yield effects produced by this approach, the U of I Crop Sciences team evaluated treatment effects on kernel population and weight. The results showed as each advanced factor was withheld from the advanced system, kernel fill decreased. Kernel weight seemed to be affected only by strobilurin fungicide application.

The greatest factor affecting higher corn yield was the inclusion of Bt-trait hybrids, which accounted for a 4.5 percent boost – or an 8.7 percent decrease when withheld. Today, approximately 85 percent of corn planted in Illinois contains the Bt trait. But that was not the case when the study was conducted on two university research plots during the 2009 and 2010 growing season.

The time elapsed since the study was completed and its March 16 online summary publication by U of I extension has resulted in some criticism in crop science circles about the study’s relevance. But on April 27, Gentry defended the study – with a caveat. "In 2009 to 2010 when the study was conducted, only about 50 or 60 percent of corn planted in Illinois contained stacked-gene traits. The use of Bt traits has increased so dramatically since then," she said. "But the study is still relevant.

"The real take-homes from the research are that increasing corn yields and closing the corn yield gap are most effectively achieved with a systems approach, not a single management practice. Secondly, farmers need to examine all of the management factors as a system."

The study, Evaluating Management Factor Contributions to Reduce Corn Yield Gaps, can be read online at www.agronomy.org/publications/aj/articles/107/2/495