Potassium fertilisation has increased cotton yields by up to 70% in potassium-deficient soils, with fibre elongation and strength identified as the lint quality parameters most strongly linked to potassium availability, new research from Arkansas field trials has found. Ten field trials across two growing seasons have reinforced existing fertilisation recommendations while establishing new tissue-testing thresholds for in-season crop nutritional monitoring.
- Potassium deficiency has grown more prevalent across the U.S. Cotton Belt over the past decade as modern, high-yielding cotton cultivars place greater nutrient demands on soils.
- Trials recorded no yield response in soils with optimum potassium availability, confirming that fertilisation benefits are concentrated in deficient soils where nutrient levels fall below recommended thresholds.
- Petiole potassium concentrations, measured in the small, stalk-like structure connecting the broad leaf to the plant's main stem, showed a stronger relationship with relative cotton yield throughout the growing season than concentrations measured in the leaf.
- The primary findings have been published in 'Furrow-irrigated cotton yield and fiber quality response to potassium fertilization' in the Soil Science Society of America Journal, by Maria Paula R Prado and Gerson Drescher.
BEHIND THE RESEARCH: Potassium's effect on cotton yield, fibre quality, and in-season nutritional monitoring has been examined across ten field trials at three Arkansas locations during the 2023 and 2024 growing seasons, with findings published across two papers by researchers at the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas Division of Agriculture.
- Maria Paula R. Prado, a former graduate student in the Arkansas Soil Fertility programme and Drescher's lab, served as first author on both papers, with Gerson Drescher, assistant professor of soil fertility, as principal researcher.
- Yield and fibre quality findings were published in the Soil Science Society of America Journal; critical leaf- and petiole-potassium concentrations for cotton nutritional monitoring were published in the Agronomy Journal.
- The "build and maintain" fertilisation philosophy, used by the Division of Agriculture, is a two-step strategy that builds low soil nutrient values to an optimum level and maintains them by replacing the amount crops remove at harvest.
- Trials were conducted across three Arkansas locations during the 2023 and 2024 growing seasons, using soils classified at varying potassium levels from very low through to optimum availability.
WHAT THE SCIENCE SHOWS: Potassium plays a direct role in plant photosynthesis and water regulation, both of which govern fibre development and lint yield. Drescher noted that lint turnout is positively affected by potassium fertilisation, and that fibre elongation and strength are more strongly related to potassium availability than other lint quality parameters. Critical potassium concentrations in plant tissue had not previously been established for modern cotton cultivars, and sampling guidance had been limited to a few growth stages.
- Petiole sampling is recommended as the primary tissue indicator because its potassium concentrations maintain a stronger yield relationship across more growth stages than leaf sampling alone.
- Season-long testing of both the leaf and the petiole is recommended, as each provides complementary information on crop potassium status at different points in the growing season.
- Growers can now use the identified concentrations to assess whether their potassium fertilisation programme is adequate and whether the crop requires additional fertiliser to reach its full yield potential.
- Ongoing research is defining the window of opportunity to correct potassium deficiency in-season and calibrating fertiliser rates for in-season applications.
WHAT THEY SAID
With this new tool, growers can now assess the adequacy of their potassium fertilisation programme and determine whether the crop needs additional fertiliser to maximise yield potential. Ongoing research is defining the window of opportunity to correct potassium deficiency in cotton and rescue yield potential, and calibrating fertiliser rates for in-season potassium applications.
— Gerson Drescher
Assistant Professor of Soil Fertility, Department of Crop, Soil and Environmental Sciences
Arkansas Agricultural Experiment Station, Division of Agriculture
University of Arkansas
