Potassium reserves in a sandy clay soil from the Saxmundham experiment - kinetics and equilibrium thermodynamics

A - Papers appearing in refereed journals

Goulding, K. W. T. and Talibudeen, O. 1979. Potassium reserves in a sandy clay soil from the Saxmundham experiment - kinetics and equilibrium thermodynamics. Journal of Soil Science. 30 (2), pp. 291-302.

AuthorsGoulding, K. W. T. and Talibudeen, O.
Abstract

Potassium‐calcium exchange equilibria in, and the kinetics of K release from, soil from the Nil and PK treatments of the Saxmundham Experiment, Rotation 1, and the Ga, Ca + K and K saturated panicle size fractions of the soils were investigated.

The free energy and enthalpy ot exchange showed K preference in all the solids. Selectivity for K decreased with increasing particle size and pre‐treatment with K salts. A comparison of the ‘differential enthalpy of exchange: per cent K saturation’ relationship for the whole soil with those of the particle size fractions suggests that soil dispersion during particle size separation also decreased K selectivity significantly. When related to the mineralogical composition of the soil, the differential enthalpy data suggest that maximum K. selectivity is associated with a vermiculite/smectite component of inter‐stratified minerals in the soil.

Isotopic exchange using 4sCa on the decalcified solids showed a measurable rate of exchange for the Ca forms of the <0.2 and 0.2–2 /μm fractions. This is attributed to traces of blocking materials (CaCO3 or hydroxy‐aluminium polymers), which are removed or rendered porous during treatment with dilute KCl solution, so that isotopic exchange with Ca is then much more rapid.

The kinetics of K extraction with a Ca saturated resin, interpreted on the basis of a three‐compartment model, suggest that sorbed K and K released by ‘fast’ and slow processes, representing sites of low and high K selectivity, were associated with minera‐logically distinct phases in the various particle size fractions.

KeywordsSoil Science
Year of Publication1979
JournalJournal of Soil Science
Journal citation30 (2), pp. 291-302
Digital Object Identifier (DOI)doi:10.1111/j.1365-2389.1979.tb00986.x
Open accessPublished as non-open access
Output statusPublished
Publication dates
Print01 Jun 1979
Copyright licensePublisher copyright
PublisherWiley
ISSN0022-4588

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