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Diffusion Kinetics of Multinutrient Accumulation by Mixed‐Bed Ion‐Exchange Resin
Author(s) -
Yang Jae E.,
Skogley Earl O.
Publication year - 1992
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/sssaj1992.03615995005600020011x
Subject(s) - diffusion , nutrient , chemistry , kinetic energy , ion , kinetics , ion exchange resin , analytical chemistry (journal) , thermodynamics , chromatography , inorganic chemistry , organic chemistry , physics , quantum mechanics
Conventional batch or miscible‐displacement methods for studying nutrient release in the soil‐solution‐root continuum have been confined to single‐ion‐release reactions that result in the disintegration of concentration gradients due to excessive water and chemicals used in the procedure. The Phytoavailability Soil Test (PST) accumulates all nutrients simultaneously, as a function of diffusion to a mixed‐bed resin sphere. Objectives of this research were to compare kinetic models to describe empirically multinutrient accumulation by the PST method, and to test its sensitivity to conditions that influence diffusion kinetics. Accumulation of nutrients by resin was measured by inserting resin spheres into saturated soil pastes for 96 h at 25, 35, or 45°C, and stripping resin‐accumulated nutrients with HCl. Existing kinetic models all described multinutrient accumulation, except for NO 3 ‐N. The parabolic diffusion law model consistently provided the best fit. Values for reaction rates and net reaction energy ( E an ) were of similar magnitude to those reported in the literature. Positive values of ΔG o ‡ and ΔH o‡ and negative values of ΔS o ‡ (pseudo thermodynamic parameters) for K and P accumulation were similar to those reported for release of these nutrients. Significant relationships were found between rate constants of K, P, S, and NH 4 ‐N and respective ion activities in soil solution. Accumulation of all nutrients was directly related to temperature, except NO 3 ‐N, which was temperature and soil specific. These results suggest that the PST method has advantages over conventional methods for measuring nutrient dynamics, as it more closely simulates field conditions, while providing for multinutrient studies.