A Midwestern soybean field dotted with 12-foot metal poles are monitoring an invisible array of light emitted by crops. This light can reveal the plants’ photosynthetic performance throughout the growing season, according to newly published research by the University of Illinois.

“Photosynthetic performance is a key trait to monitor as it directly translates to yield potential. This method enables us to rapidly and nondestructively monitor how well plants perform in various conditions like never before,” said Kaiyu Guan, an assistant professor in the DNR and Environmental Sciences at U of I.

The Illinois team reports on the first continuous field season to use sun-induced fluorescence (SIF) data to determine how soybeans respond to fluctuating light levels and environmental stresses.

“Since the recent discovery of using satellite SIF signals to measure photosynthesis, scientists have been exploring the potential to apply SIF technology to better agricultural ecosystems. 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,” said study collaborator Carl Bernacchi, an associate professor of plant science.

A network of SIF sensors has been deployed across the U.S. to evaluate croplands and other natural ecosystems. Guan’s lab has launched two other long-term SIF systems in Nebraska to compare rainfed and irrigated fields in corn-soybean rotations. “By applying this technology to different regions, we can ensure the efficacy of this tool in countless growing conditions for a myriad of plants,” said Xi Yang, an assistant professor at the University of Virginia, who designed this study’s SIF monitoring system.

One to two percent of the plant’s absorbed light energy is emitted as fluorescent light that is proportional to the rate of photosynthesis. Researchers capture this process using hyperspectral sensors to detect fluctuations in photosynthesis over the growing season. They designed this continuous study to better understand the relationship between absorbed light, emitted fluorescent light, and the rate of photosynthesis.

A network of SIF sensors has been deployed across the U.S. to evaluate croplands and other natural ecosystems. Guan’s lab has launched two other long-term SIF systems in Nebraska to compare rainfed and irrigated fields in corn-soybean rotations. “By applying this technology to different regions, we can ensure the efficacy of this tool in countless growing conditions for a myriad of plants,” said Xi Yang, an assistant professor at the University of Virginia, who designed this study’s SIF monitoring system.