Scientists with the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture, recently published a study in Smart Agricultural Technology providing proof-of-concept that hyperspectral sensors like a spectroradiometer can help in quantifying herbicide effectiveness, a critical element of weed management that helps curb herbicide resistance.
While normal cameras use three visible light bands — red, green and blue — to create images in the spectral range of 380 to 750 nanometers, hyperspectral sensing captures bands ranging from 250 nanometers to 2,500 nanometers and thermal infrared.
The researchers used this technology to evaluate how common lambsquarters responded to glyphosate. They also turned up empirical evidence that photosynthesis in the plant actually increased when exposed to a sub-lethal dose of the herbicide. Common lambsquarters — Chenopodium album L. — is a weed in agricultural and garden settings.
“Plant response to herbicide application is measured using visual ratings, but accuracy varies with the quality of training and years of practice of the rater,” said principal investigator of the study Aurelie Poncet, assistant professor of precision agriculture in the crop, soil and environmental sciences department for the Division of Agriculture and the Dale Bumpers College of Agricultural, Food and Life Sciences. “We thought, if we could have a sensor that automates some of this decision, we might be able to implement it into applications down the road.”
Weed scientists are trained to rate herbicide efficacy within a 10 percent margin of error, plus or minus 5 percent. The researchers were able to use machine learning models on data collected with a spectroradiometer to reach a margin of error of 12.1 percent. Their goal is to get below 10 percent.
The researchers used a random forest machine learning algorithm to analyze thousands of vegetation index data points collected in the experiment. The algorithm combines the output of multiple decision trees to reach a single result.
“Our success using random forest to describe common lambsquarters response to glyphosate application opens the possibility of moving beyond the development of vegetation indices, another approach gaining traction in the published literature,” said Mario Soto, lead author of the study and a crop, soil and environmental sciences master’s student in Bumpers College.
Next steps Once refined, hyperspectral sensing could be used to measure specific weed response to herbicide application and overcome limitations of a human’s visual assessment. Further development of the method and validation may also be used to create a platform for high-throughput categorization of weed response to herbicides and screening for herbicide resistance, the study’s authors noted.
While training can overcome lack of experience for evaluators, mental and physical fatigue from long workdays evaluating treatments in harsh environmental conditions can affect judgement for even the most experienced evaluator, said Nilda Roma-Burgos, professor of weed physiology and molecular biology for the experiment station and Bumpers College.
“This method, in principle, could remove the human factor in herbicide efficacy evaluations and will be an invaluable research tool for weed science,” said Burgos, a co-author of the study. “Meanwhile, much work still awaits to validate the method across key weed species, herbicide modes of action, time after herbicide application and environmental conditions.”
Co-authors of the study included Kristofor Brye, University Professor of applied soil physics and pedology; Wesley France, program associate, and Juan C. Velasquez, weed science graduate research assistant, of the crop, soil and environmental sciences department.
Cengiz Koparan, assistant professor of precision agriculture technology with the agricultural education, communication and technology department and the biological and agricultural engineering department, and Amanda Ashworth, research soil scientist with the U.S. Department of Agriculture’s Agricultural Research Service, were also co-authors.
The hyperspectral imaging study was supported in part by the National Science Foundation’s NSF-SBIR Phase II Award No. 2304528 and the USDA’s National Institute of Food and Agriculture, Hatch projects ARK0–2734 and ARK0–2852.
To learn more about the Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website. Follow us on X at @ArkAgResearch, subscribe to the Food, Farms and Forests podcast and sign up for our monthly newsletter, the Arkansas Agricultural Research Report. To learn more about the Division of Agriculture, visit uada.edu. Follow us on X at @AgInArk. To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit uaex.uada.edu.
About the Division of Agriculture The University of Arkansas System Division of Agriculture’s mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation’s historic land grant education system.
The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on three system campuses.
Pursuant to 7 CFR § 15.3, the University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services (including employment) without regard to race, color, sex, national origin, religion, age, disability, marital or veteran status, genetic information, sexual preference, pregnancy or any other legally protected status, and is an equal opportunity institution.
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Media Contact: John Lovett
U of A System Division of Agriculture
Arkansas Agricultural Experiment Station
(479) 763-5929
jlovett@uada.edu
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