AVAILABILITY OF POTASSIUM TO RYEGRASS FROM SCOTTISH SOILS II. UPTAKE OF INITIALLY NON‐EXCHANGEABLE POTASSIUM

A. H. SINCLAIR*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

The stable desorption parts of soil Quantity/Intensity isotherms were used to determine the contributions of initially exchangeable and non‐exchangeable potassium to plant uptake from ten soils. The activity ratio, ARK= aK/√aCa, Mg at which K was first taken up from non‐exchangeable sources varied from 3 × 10−3 to 8 × 10−3 M1/2 depending on the soil. Uptake rates of two categories of initially non‐exchangeable K were linearly related to √times;. The first category appeared to be close to equilibrium with the initially exchangeable K, and gave effective diffusion coefficients of 10−7 cm2 s−1 for four soils. The second category gave diffusion coefficients from 10−20 to 10−22 cm2 s−1, probably came from internal surfaces of micaceous clays, and began to be released at activity ratios below 3 × 10−4 to 6 × 10−4 M1/2 depending on soil type. The soils fell into three groups, broadly consistent with soil series, on their ability to release the second category of potassium.

Original languageEnglish
Pages (from-to)775-783
Number of pages9
JournalJournal of Soil Science
Volume30
Issue number4
DOIs
Publication statusPrint publication - Dec 1979
Externally publishedYes

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