Twelve-foot metal poles with long outstretched arms dot a Midwestern soybean field to monitor an invisible array of light emitted by crops.
New research by the University of Illinois shows this light can reveal the plants' photosynthetic performance through the growing season.
"Photosynthetic performance is a key trait to monitor as it directly translates to yield potential," said Kaiyu Guan, an assistant professor in the Department of Natural Resources and Environmental Sciences at U of I and the principal investigator of this research. "This method enables us to rapidly and nondestructively monitor how well plants perform in various conditions like never before."
The Illinois team reports on the first continuous field season to use sun-induced fluorescence, or SIF, data to determine how soybeans respond to fluctuating light levels and environmental stresses.
"This research advances our understanding of crop physiology and SIF at a local scale, which will pave the way for satellite observations to monitor plant health and yields over vast areas of cropland," study collaborator Carl Bernacchi said.
Photosynthesis is the process in which plants convert light energy into sugars and other carbohydrates that eventually become our food or biofuel, but 1 to 2 percent of the plant's absorbed light energy is emitted as fluorescent light, and that emitted light is proportional to the rate of photosynthesis.
Researchers capture this process using hyperspectral sensors to detect fluctuations in photosynthesis over the growing season.
"We are also testing the applicability of this technology for crop phenotyping to link key traits with their underlying genes," co-author Katherine Meacham said.
"SIF technology can help us transform phenotyping from a manual endeavor requiring large teams of researchers and expensive equipment to an efficient, automated process," co-author Caitlin Moore said.
Rye cover crop promising in edamame
Cover crops offer a potential weed management tool, but use in specialty crops is limited.
A new University of Illinois study reports that early-killed cereal rye shows promise for edamame growers.
"Early-killed rye reduced weed density by 20 percent and suppressed early-season weed growth 85 percent," said Marty Williams, an ecologist with the Department of Crop Sciences at U of I and the USDA Agricultural Research Service.
Edamame is notoriously hard to get started. Its large seeds make them good for eating, but the soybean crop can suffer from low seedling emergence in the field. Williams wasn't sure asking them to struggle through a layer of cover-crop residue would work.
Williams and his research team conducted a three-year field experiment testing 11 edamame cultivars and multiple fall-seeded cover crops -- oilseed radish, winter canola and cereal rye.
Only early-killed rye offered the right combination of conditions to suppress weeds and allow edamame to emerge easily. Others allowed emergence but didn't control weeds, or suppressed both weeds and edamame.
"Early-killed rye resulted in a relatively thin layer of cover-crop residue. With thicker layers of residue, you start to have problems with crop emergence. But with no cover-crop residue, there's no weed control benefit," Williams said. "Early-killed rye provided the sweet spot."