Growers realize the importance of strong corn roots. Roots, however, do more than anchor corn securely in the soil. They take up moisture and nutrients, allowing the plant to develop.
"Corn breeders work to develop yield potential in a hybrid, but realizing that yield requires a root structure that protects and stabilizes yields," says Jeff Schussler, DuPont Pioneer research scientist. "Root architecture is critical."
Pioneer researchers are working to develop better corn root architecture with plenty of fine hair roots to absorb nutrients near the surface and deep-branching roots to access moisture from lower levels of the soil.
Roots are complex. Each corn plant has tens of thousands of tiny roots. Because they're underground, they're hard to study, so researchers don't understand root development as well as they'd like.
But understanding root growth is a key to increasing yields. When a plant puts more energy into root growth, it generally leaves less available for grain production.
"When I talk about corn roots, I suggest we need ‘steep, cheap and deep' roots," says Jonathan Lynch, professor of plant nutrition at Penn State University. "First, we need them to quickly go downward into the soil rather than grow primarily laterally (steep). Second, we need them to grow in a manner that puts less strain on the plant, a metabolic rate that doesn't overtax the plant and detract from ear production. Certain anatomical traits can make capture of nutrients ‘cheaper' for the plant. Finally, we need the ability to go deep for water if conditions demand it."
Genetics offer root diversity
Corn genetics contain tremendous diversity for root architecture and development functions. Lynch notes this provides a great opportunity to learn more and improve root performance.
"Corn roots may be steep or shallow in their growth orientation, they may be thick or thin, they may have lots of fine root hairs or few," Lynch reports. "There's a greater difference in corn plant appearance underground than above ground."
Not all roots are equal. While the growth of primary and nodal roots continues as the soil dries, the growth of lateral (branch) roots may be inhibited. Researchers are asking which roots need to grow more efficiently and when, given the wide range of environmental conditions the plant may face during the growing season.
Lynch notes drought is the biggest limit to yields for U.S. growers. "We may be getting less than half of modern hybrids' yield potential, mainly due to water stress," he says. "As rain patterns and climates change, we'll need to consider ways to limit the impact of these stresses."
Pioneer has developed Optimum® AQUAmax™ hybrids to boost corn performance in these water-limited environments. Native genetic variation offers higher yields under low-moisture conditions. Pioneer is characterizing the root architecture of these hybrids to learn more about why they perform. This will help improve roots in new hybrids.
"We're using virtual root phenotyping," Schussler reports. "We place probes in the soil and measure water uptake to determine where the roots are. One hybrid may grow an inch per day in a dry environment, while another grows 1.5 inches." The goal is to improve how hybrids grow, flower and yield even when water supplies are limited.
Flexible or "plastic" roots do a better job of maintaining water and nutrient uptake, notes Bob Sharp, professor of plant sciences at the University of Missouri. Achieving balance is complicated. "We may find optimal nutrient uptake requires one type of root architecture while optimal water uptake requires another."
"We're still learning," Schussler adds. "Root response to dry zones can be unpredictable. We know some hybrids respond differently, some handle stress better. We're trying to develop root systems that access and utilize water more efficiently."
Rooting for your roots
Growers can make management decisions that impact corn root performance. Here are some tips from Jonathan Lynch of Penn State University.
In 223 on-farm comparisons, product advancement tests and research trials in 2008-2010 in water-limited environments concentrated in NE, CO, KS and TX and controlled stress evaluations in California and Chile, Optimum®AQUAmax® hybrids were tested against leading commercially available competitor and Pioneer hybrids. Optimum AQUAmax hybrids demonstrated a 5.0 percent average yield advantage over the leading commercial hybrids tested. Water-limited environments are those in which the water supply/demand ratio during flowering or grain fill was less than 0.66 on a 0-1 scale (1 = adequate moisture as determined by Pioneer) using Pioneer's proprietary EnClass®system and in which the average yield of the commercially available hybrids was less than 150 bu/acre. Moisture levels were measured either at trial location or the nearest weather station. Product performance in water-limited environments is variable and depends on many factors such as the severity and timing of moisture deficiency, heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. All hybrids may exhibit reduced yield under water and heat stress. Individual results may vary.