image: Research at the Arkansas Agricultural Experiment Station determined the cardinal temperatures — base, optimal and maximum — of eight cover crops, including crimson clover.
Credit: U of A System Division of Agriculture photo by Mila Pessotto
FAYETTEVILLE, Ark. — Knowing what temperatures that a plant can withstand is a hallmark of botanical science, but those temperatures had not been well documented for many cover crops.
Grown in periods of the year when the cash crop is absent, cover crops are planted for erosion control, as well as weed suppression and to improve soil structure, moisture retention and nutrient cycling. They also provide habitat for beneficial insects and can serve as forage for farm animals.
Without knowledge of the cover crops’ base, optimal and maximum temperature ranges —known as cardinal temperatures — agricultural scientists could not develop accurate plant growth and biomass prediction models, which help farmers optimize decisions like when to terminate the cover crop. The models also help assess weed suppression, estimate nutrient cycling and quantify the benefits of soil carbon and potential negative impacts of a cover crop.
A team of researchers with the University of Arkansas System Division of Agriculture, led by Trent Roberts, professor of soil fertility and soil testing and Endowed Chair in Soil Fertility Research in the crop, soil and environmental sciences department, took on the problem by evaluating eight commonly grown cover crop species in growth chambers to find their cardinal temperatures.
The base temperature is the lowest temperature at which the plant will still exhibit a measurable growth rate. Optimal is where plant growth is at its peak, and maximum is the temperature at which plant growth ceases due to excessive heat. For many plant species, the relationship between temperature and growth rate or developmental stage can be correlated and predicted using mathematical models.
Not only did the researchers identify the base temperatures for two cover crop species and the optimum temperatures for three of the eight cover crop species for the first time, they also determined the maximum temperature values of all eight cover crops, which included crimson clover, Austrian winter pea, balansa clover, barley, black-seeded oats, common vetch, cereal rye, crimson clover and hairy vetch.
Estimates were required for maximum temperatures of five of the cover crop species due to the 34 Celsius upper limits of the growth chamber. Although maximum temperatures may not be as critical for growth modeling as the base and optimum temperatures, the researchers pointed out that knowledge of the maximum temps may be more crucial in the Mid-South and Southern states, where temperatures can rise quickly in late winter and early spring.
In all, they offered 14 newly identified cardinal temperatures for the eight cover crop species. Five cardinal temperatures determined in the study were different from what was previously recorded and three of the base temperature values were found to differ from previously reported values, including cereal rye, which was almost 9 degrees Celsius lower than the previously reported value in the scientific literature.
“Such a large difference in base temperature values would lead to gross underestimations of plant growth and development for cereal rye when using the data reported in the literature," said Roberts, whose role includes research and outreach work through the Division of Agriculture’s Arkansas Agricultural Experiment Station and Cooperative Extension Service.
Mila Pessotto, Ph.D., was the lead author of the research article titled “Determining Cardinal Temperatures for Eight Cover Crop Species” as a masters student in the crop, soil and environmental sciences department of the Dale Bumpers College of Agricultural, Food and Life Sciences at the University of Arkansas.
“The refinement or identification of 18 of the 24 possible cardinal temperatures investigated in this study generates a significant step forward in the ability to model cover crop species growth and development,” Pessotto said.
Tri Societies Recognition
The work, originally published in 2023, recently earned Pessotto and her collaborators a 2025 Outstanding Paper Award from the American science societies for crop, soil and agronomy.
The American Society of Agronomy, the Crop Science Society of America, and the Soil Science Society of America — also known as the Tri Societies — recognize outstanding publications from their journals each year based on advancement of knowledge in the profession, effectiveness of communication, methodology, originality and impact.
Co-authors of the study included Roberts, Mary Savin, professor and horticulture department head, Matt Bertucci, assistant professor of sustainable fruit and vegetable production in the horticulture department, Jeremy Ross, professor and extension soybean agronomist, and Caio dos Santos, who received a master’s degree from the University of Arkansas in 2020.
Pessotto is now a postdoc research associate in the department of agronomy at Iowa State University, where dos Santos also recently earned his doctorate.
The study was supported with funding and technical assistance from the Arkansas Corn and Grain Sorghum Board and the Arkansas Soybean Promotion Board.
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.