As corn yields climb across the U.S., farmers face a growing challenge: managing the massive amount of crop residue left behind. But within that challenge is an opportunity, according to University of Illinois researchers. Their work indicates that farmers who pair their tillage practices and residue management strategy with the root architecture of their specific corn hybrids can boost yield even more.
Connor Sible, research assistant professor at the university, says a good starting point in the process is recognizing what higher yields mean for residue levels in the field. Assuming an average harvest index of about 52% give or take, he notes that every bushel of corn you produce sends 44 pounds of dry matter out the back end of your combine.
You might say “no big deal” but that’s not the case. As Sible tells corn growers who question whether that’s significant: “Have your yields gone up 10 bushels? If so, now that’s 440 pounds per acre. If your yield’s 20 bushels higher, that’s almost 1,000 pounds per acre more residue on your field that you may be tilling or managing the same way you have for the last 20 years.”
Sible’s point is if your yield trend over the last decade or so has moved upward, you can assume your residue load has increased as well – and it’s probably time to rethink how you manage it.
Defining Root Architecture
The other side of the conversation about residue management is root architecture. Sible describes corn root systems as having three characteristics to consider: surface area, root angle and root mass.
“The surface area is how fibrous those roots are,” he says. “With root angle, consider are they wide angle, sometimes described as umbrella roots? Or, are they narrow-angle roots that grow deep? And then we look at the pure mass, how dense the roots are.”
What Sible and his team have determined is that wide, shallow root systems are usually most responsive to nutrients placed near the soil surface. The reason: these roots occupy the same zone where surface-applied or banded nutrients tend to accumulate in no-till or high-residue systems.
“The wider-angled roots are more responsive to split-applied nitrogen,” Sible says, as a for instance. “Those ‘umbrella roots’ are wide. They’re in the surface profile, so sidedress N goes right to where the roots are.”
In contrast, narrow, deeper root systems often perform better when nitrogen is placed deeper. In drought-prone environments or where nitrogen is placed deeper, these hybrids are genetically built to chase water and mobile nutrients moving downward, offering an advantage over the wide-angle root system.
Genetic Consistency Across Environments
One of the most striking findings from Sible’s research is how stable the root “personalities” are in the field. A PhD-level student Sible works with at the university, Sam Leskanich, determined this personality stability through field research.
Sible says Leskanich planted the same hybrids across different sites and years and then ranked the hybrids relative to each other. Whether at a southern Illinois test site with 1.8% to 2.0% organic matter and then at a northern Illinois site with organic matter above 3.5%, across dry and wet years, corn hybrids characterized as having narrow root systems stayed narrow, and wide-rooted hybrids remained wide.
The environment changes the overall size and development of the root system, but “it doesn’t change a specific hybrid’s natural rooting approach,” Sible says. That suggests root architecture is controlled by genetics.
A Call for More Data
For farmers, the practical implication is that hybrid root architecture should be matched to their production system by field. For instance, Sible and team contend that farmers might benefit from considering where water and nutrients tend to be available in their particular system, then select hybrids whose rooting patterns are well-suited to that system.
Sible adds that he believes a long-term opportunity lies in encouraging seed companies to share more information about their hybrids’ root architecture. Sible believes that adding root information to hybrid descriptions—such as surface area, angle and mass—would help farmers match hybrids not only to geography and maturity zones but also to tillage, residue level and fertility placement strategies. (Learn what Beck’s Hybrids is doing in this area here.)
Until this type of information is readily available from companies, carefully designed on-farm test comparisons across residue levels, tillage systems and fertilizer placements remain the best way for individual farmers to learn where each hybrid performs best.
As Sible puts it, “If you pick the right hybrid for your system, that can make you get a few more bushels out of what you’re already doing.”
To hear more about the University of Illinois research on corn roots, residue and nutrient management, check out Sible’s recent discussion with Mark Licht, Iowa State University Extension, here.
