The plant’s contribution from below ground is increasingly a focus to manage hybrids for maximum yield
Farmers know the importance of a good root structure for their corn plants, but do we know all there is to know on how roots contribute to yield?
From the lab to the field, new efforts are piecing together how knowing more about roots can lead to better management and higher yields.
Researchers at a USDA–Agriculture Research Service (ARS) laboratory are taking a 3-D approach to studying roots—literally.
Leon Kochian is director of the USDA–ARS Robert W. Holley Center for Agriculture and Health on the Cornell University campus in Ithaca, N.Y. His team has developed the RootReader 3-D platform, a root growth, imaging and analysis system that grows plants in cylinders with the roots growing in a gel or nutrient solution. The root systems are photographed on a computer-controlled rotating platform to capture 100 images as the plant is rotated 360°. The RootReader 3-D software automatically reconstructs the 100 2-D images into a 3-D view to measure the roots to better study their structure and architecture.
This sorghum plant is growing in a hydroponic cylinder system used for analyzing root systems with unique nutrient and stress regimes.
"Researchers and those in the seed industry are realizing that we need to know what root systems do. In our research, we score 20 different traits, including root length, thickness and angle, as well as traits that measure the shape and structure of the entire root system" Kochian says.
This three-dimensional platform was developed in 2007 and has been in use in its current setup since 2010. Kochian’s lab has studied rice, sorghum and corn.
"This approach allows us to look at the whole root system as it develops in the first 20 days
of growth," he explains. "In the architecture of the root system is a trait called centroid, which is the vertical position of the center of mass and a quantitative measure of the depth of the root system."
Gold down under. Knowing more about root structure and what goes on beneath the surface will lead scientists to a better understanding of the plant’s nutrient uptake ability.
"In the past, the focus has been on the plant’s characteristics above ground, but we’re interested in increasing the effectiveness of the below-ground root system to absorb nutrients," Kochian says. "One issue that has brought a lot of attention to this type of research has been the recent droughts and water shortages. But we can also look at how to improve the plant’s ability to take up phosphorus and nitrogen from the soil, based on its root structure."
Phosphorus is not a very mobile nutrient within the soil, so a plant that has more shallow roots will be able to capture phosphorus that resides in the top layer of the soil, Kochian notes. Conversely, deeper roots will be able to capture more nitrogen and water, which moves much faster down through the soil profile.
"We have been able to genetically map these traits and have found regions of the plant
genome where specific DNA sequences appear to control deep versus shallow and compact versus spread-out root structures," Kochian explains. "We don’t know what type of root system shape and architecture is important until we test in the field, but this system allows us to capture the foundation for that research. Genetics are an important part, but environment will also obviously always impact how roots grow."
Field studies. The known limitation of this lab research is the controlled environment—soil in the field can widely vary and impact root growth. To translate lessons learned in the lab to research in the field, seed companies are picking up the baton. Companies such as Beck’s Hybrids and AgriGold have expanded their research efforts focusing on roots.
"At Beck’s, we measure the roots according to what the farmer will see in the field," says Doug Clouser, product lead for the company. "Because the environment plays a significant role in the development and structure of roots, we look at the overall root strength when we’re evaluating a hybrid’s performance."
AgriGold is working to categorize its hybrids by their root type and develop a scale to rate the root system.
"There is more to understand about roots to unlock yield potential and consistent hybrid performance," says Mike Kavanaugh, AgriGold agronomy manager. "Root structure could explain things that happen above ground, which are the result of the type of root systems that are underneath."
Kavanaugh says AgriGold’s system will establish a scale from 1 to 10—1 being a really fibrous root system with a wide base, lots of fine roots and more shallow by nature, and 10 being a deeply penetrating root system made up of coarse roots and much more narrow in overall structure.
"So far, we’ve seen that hybrids with strong coarse textured roots with the ability to go deep can pick up some much-needed water late in the season. On the other hand, some of the hybrids in our lineup that seem to do well in poorly drained environments have a more fibrous shallow root system," he says.
The challenge for AgriGold is establishing a standard environment since that variable can dramatically affect root growth. "We’ve tried different ways to categorize our hybrids for several years now. This summer we continue to evaluate root structure in our own field trials while working with university partners," Kavanaugh says.
Root selections. The end goal is to have this information included in future hybrid profiles so agronomy teams can help farmers place hybrids for maximum yield and performance, Kavanaugh notes.
"The reason why we’re doing this is because we realize that each year is different. Some years are dry, and some years are wet. There’s no reason to throw a hybrid out of consideration because we’ve had a wet season or a dry season. One has to look at the overall picture," Kavanaugh says.
In addition to water management, this research could result in better nutrient efficiency and hybrid placement for maximum yields. The company already categorizes its hybrids by families—and those characteristics include nitrogen timing, plant densities and other agronomic traits.
"Knowing those performance attributes gives our team tools to share with corn growers to better place our hybrids," he explains. "We’re looking to evaluate why hybrids respond to the environment the way they do, what the different styles of root are in the hybrids, then picking the hybrids with the root system in mind will give us more consistent results."
More information about root systems might change farmers’ management decisions. "Root structure is critical as farmers fine-tune their corn management decisions. Fibrous root systems that spread out may perform better in wider rows because the roots can gather water and nutrients from further distances from the plant," says Kevin Cavanaugh, director of research at Beck’s Hybrids. "Conversely, roots that go deep into the soil may benefit more from narrow rows or possibly from later nutrient applications when the nutrients move into a lower zone for uptake.
This research can be very helpful to maximize yield potential."
It comes down to producing more with less, USDA’s Kochian adds. "Farmers are asking for consistent yields despite water or nutrient shortages," he says. "We’ll be able to give them more opportunities because of the interest in the root traits and how that leads to better management."
You can e-mail Margy Eckelkamp at firstname.lastname@example.org.