Single empirical relationship for potassium exchange equilibria in various soils

The exchange behavior of K ions was studied in a collection of 40 soil samples from southern Belgium. These soils are characterized by wide differences of mineralogical composition, cation exchange capacity (CEC), and base saturation percentage. The prevailing basic cations on the exchange complexes...

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Bibliographic Details
Published in:	Soil Science Society of America journal Vol. 51; no. 4; pp. 918 - 920
Main Authors:	Dufey, Joseph E., Marot, Jean M.
Format:	Journal Article
Language:	English
Published:	Madison, WI Soil Science Society of America 01-07-1987
Subjects:	adsorcion adsorption Agronomy. Soil science and plant productions belgica belgique belgium Biological and medical sciences Biometrics, statistics, experimental designs, modeling, agricultural computer applications Chemical, physicochemical, biochemical and biological properties cultural soil types Fundamental and applied biological sciences. Psychology Generalities. Biometrics, experimentation. Remote sensing Mineral components. Ionic and exchange properties modele modelos Physics, chemistry, biochemistry and biology of agricultural and forest soils potasio potassium Soil science tipos cultivables de suelos type de sol de culture Cation exchange Clay Europe Saturation Empirical relation Inorganic ion Chemical base Minerals Western Europe Chemical equilibrium Soil Ion exchange Mathematical model Potassium Physicochemical properties
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Summary:	The exchange behavior of K ions was studied in a collection of 40 soil samples from southern Belgium. These soils are characterized by wide differences of mineralogical composition, cation exchange capacity (CEC), and base saturation percentage. The prevailing basic cations on the exchange complexes are Ca, Mg, and K; Na is negligible. The Gapon formalism (i.e., exchangeable K ratio, EKR, vs. K adsorption ratio, KAR) is used to describe the relationship between the K concentrations in the surface and solution (water extract at 1:3 soil/H2O ratio) phases. When EKR is expressed (as it is usual) as [K]i/([Ca]i + [Mg]i)‐[ ]i refers to surface concentrations, molckg−1—the dispersion of the experimental points around the line EKR vs. KAR is very high. However if EKR is expressed as [K]i/(CEC − [K]i), a fair linear relationship with low statistical dispersion is observed. This relationship shows that the exchange equilibria of K in our soils cannot be simply regarded as a K vs. (Ca + Mg) exchange reaction. This is likely related to the fact that in most samples the sum of exchangeable bases was lower than the CEC. Such a single relationship, though difficult to explain, may be especially useful for modeling purpose.
Bibliography:	P P33 Contribution from the Soil Science Laboratory and the Laboratory of Grassland Ecology, Univ. of Louvain, Place Croix du Sud 2, B‐1348 LOUVAIN‐LA‐NEUVE, Belgium. Research Associate at the National Fund for Scientific Research (F.N.R.S. Belgium), and Assistant at the Catholic Univ. of Louvain, respectively.
ISSN:	0361-5995 1435-0661
DOI:	10.2136/sssaj1987.03615995005100040016x