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Mathematical Models for Potassium Release Kinetics in Calcareous Soils
Author(s) -
Havlin J. L.,
Westfall D. G.,
Olsen S. R.
Publication year - 1985
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1985.03615995004900020020x
Subject(s) - silt , soil water , extraction (chemistry) , potassium , diffusion , clay minerals , chemistry , calcareous soils , montmorillonite , mineralogy , kinetics , rate equation , mica , analytical chemistry (journal) , thermodynamics , soil science , environmental chemistry , geology , chromatography , organic chemistry , physics , paleontology , quantum mechanics
Potassium release from the coarse (20–50 µm), medium (5–20 µm) and fine silt (2–5 µm), and the coarse (2–0.2 µm) and medium‐fine clay (<0.2 µm) fractions of six Great Plain soils was determined by successive extraction with Ca‐saturated cation exchange resins. All soils contained primarily montmorillonite‐mica minerals. Results indicated that 65 to 80% of the total K released in 7000 h of extraction time occurred in the clay (<2.0 µm) fraction. Four mathematical models (first‐order rate, parabolic diffusion, power function, and Elovich) were used to describe cumulative K release. Comparisons of coefficients of determination ( r 2 ) and standard errors of the estimate (SE) indicated that the Elovich, power function, and parabolic diffusion equations adequately described cumulative K release, whereas the first‐order rate equation did not. Rate constants for the three equations were highly correlated with mica content and relative alfalfa yield and K uptake. In the past, others have used complex equations containing three simultaneous first‐order rate terms to describe K release; however, results reported herein show that simple one‐term equations can be used.