Natural Potassium (K) Isotope Fractionation during Corn Growth and Quantification of K Fertilizer Recovery Efficiency Using Stable K Isotope Labeling

Xin Yang Chen, Xin Yuan Zheng, Brian L. Beard, Matilde Urrutia, Clark M. Johnson, Phillip Barak

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4 Scopus citations


An improved understanding of the potassium (K) cycle in soil-plant systems is scientifically and economically significant, but the conventional research based on K concentration measurements has several known limitations. The recent advent of high-precision stable K isotope analysis (reported as δ41K values) can facilitate the use of both stable K isotope labeling and mass-dependent isotopic fractionation in studying the K nutrient cycle, including K fertilizer utilization, and plant-soil interactions. As a proof of concept, we conducted a pot study to quantify the uptake of K fertilizer by corn. Three groups of treatment (50, 100, 200 mg K kg-1 soil) were conducted using soils premixed with different amounts of 41K-labeled fertilizer. A control group used the same soil without fertilizer treatment. Aboveground shoots and soils were sampled and analyzed after ∼6 weeks. The control group showed preferential uptake of light K isotopes by corn with an estimated mass-dependent fractionation of ∼-0.37‰ (±0.23‰) in 41K/39K between the shoot and soil. In fertilized experiments using an enriched 41K tracer, δ41K data unambiguously quantifies fertilizer-derived K in corn shoots, yielding apparent fertilizer recovery efficiency of 59-81%. In comparison, the K concentration-based method underestimated fertilizer utilization at low K treatment and overestimated fertilizer utilization at high K treatment because it cannot distinguish different K sources whose relative contributions to the bioavailable K pool in the soil can vary in response to plant-soil interactions. Our study demonstrates the potential of stable K isotopes in improving the understanding of the K cycle in soil-plant systems.

Original languageEnglish (US)
Pages (from-to)1876-1889
Number of pages14
JournalACS Earth and Space Chemistry
Issue number7
StatePublished - Jul 21 2022

Bibliographical note

Funding Information:
This work was supported by the National Science Foundation under Grant No. 1741048 awarded to B.L.B., C.M.J., and X.-Y.Z. The authors are grateful for the assistance of Zachary Tracy and Christy Davidson with the greenhouse experiments and all of the students who participated in working on the pot experiments reported here as part of their lab project to explore fertilizer usage during Soil Science 626 Mineral Nutrition of Plants class at UW-Madison.

Publisher Copyright:
© 2022 American Chemical Society.


  • corn
  • fertilizer
  • isotope labeling
  • nutrient utilization
  • potassium cycle
  • potassium isotope fractionation
  • potassium isotopes


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