Potassium Management Is Key to Maximizing Cotton Yield and Fiber Quality

With the 2026 cotton planting season in full swing, research out of the Arkansas Agricultural Experiment Station provides a fresh reminder of the importance of sufficient potassium for cotton lint yield and quality.

Over the past decade, potassium deficiency has become more common across the U.S. Cotton Belt as farmers use more modern, high-yielding cotton cultivars that have greater nutrient demands, according to Gerson Drescher, an assistant professor of soil fertility in the Department of Crop, Soil and Environmental Sciences for the experiment station, the research arm of the U of A System Division of Agriculture.

In 10 field trials conducted during the 2023 and 2024 growing seasons at three Arkansas locations, results showed that potassium fertilization increased cotton yields by up to 70% in potassium-deficient soils. No response was observed in soils with optimum potassium availability.

"The results emphasize that adequate potassium management is key to maximizing both cotton yield potential and fiber quality," Drescher said. "The study also showed that lint turnout and quality are positively affected by potassium fertilization, with fiber elongation and strength being more strongly related to potassium availability than other lint quality parameters."

Potassium is crucial for plant photosynthesis and water regulation, both of which directly affect fiber development and lint yield. 

The Soil Science Society of America Journal published the Arkansas study results as "Furrow-irrigated cotton yield and fiber quality response to potassium fertilization."

The first author was Maria Paula R. Prado, a former graduate student in the Arkansas Soil Fertility program and Drescher's lab.

Drescher said the research provides robust evidence that the potassium fertilizer rates required to maximize cotton yield in potassium-deficient Arkansas soils align with current recommendations using a "build and maintain" fertilization philosophy.

This philosophy used by the Division of Agriculture is a two-step soil fertility strategy that focuses on building low soil nutrient values up to an optimum level and then maintaining them by replacing the amount crops remove at harvest. 

Current fertilizer-potassium rate recommendations for cotton in Arkansas suggest a preplant potassium application of 140 pounds K2O per acre on soils with "very low" soil test potassium and 95 pounds K2O per acre on soils with "low" soil test potassium. 

"These results align with current recommendations that aim to maximize crop yield, provide additional potassium to build soil-test potassium and replenish nutrient removal or loss to maintain optimal soil-test potassium values," the study noted.

Season-Long Plant-Tissue Testing 

As part of their studies on potassium monitoring in cotton, Prado and Drescher also tested methods for collecting tissue samples. While plant-tissue testing is an effective tool for diagnosing crop nutritional status, critical tissue-potassium concentrations had not been established for modern cotton cultivars at the time of this study and were limited to a few growth stages. Questions remained if the sample should be taken from the leaf or the petiole, the small, stalk-like structure that attaches the broad leaf to the plant's main stem.

Having identified critical potassium levels in the leaf and petiole to maximize cotton yield potential, the study suggested that concentrations in the petiole had a stronger relationship with relative cotton yield — compared to maximum potential — than in the leaf throughout the growing season. Still, the researchers proposed season-long follow-up tests of both the leaf and petiole for potassium levels.

"With this new tool, growers can now assess the adequacy of their potassium fertilization program and determine whether the crop needs additional fertilizer to maximize yield potential," Drescher said. "Ongoing research is defining the window of opportunity to correct potassium deficiency in cotton and rescue yield potential, and calibrating fertilizer rates for in-season potassium applications."

The study's results were published in the Agronomy Journal as "Defining critical leaf- and petiole-potassium concentrations for monitoring cotton nutritional status."  

Co-authors of the studies by Prado and Drescher included graduate research assistants Gabriela Mengez and Katie French; program associates Qamar Sarfaraz and Alden D. Smartt; Fred M. Bourland, professor of plant breeding and genetics and the Altheimer Chair for Cotton Research and Development; Trenton Roberts, a professor of soil fertility and testing and Endowed Chair in Soil Fertility Research; and Nathan Slaton, associate vice president for agriculture and associate director of the Arkansas Agricultural Experiment Station.

Research funding support was provided by Cotton Incorporated, administered by the Arkansas State Cotton Support Group, and Fertilizer Tonnage Fees administered by the Arkansas Soil Test Review Board. The work was also supported by the U.S. Department of Agriculture National Institute of Food and Agriculture, Hatch Project 2800.

To learn more about ag and food research in Arkansas, visit aaes.uada.edu. Follow the Arkansas Agricultural Experiment Station on LinkedIn and sign up for our monthly newsletter, the Arkansas Agricultural Research Report. To learn more about the Division of Agriculture, visit uada.edu. 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 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 22 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 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.