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Determination of Available Interlayer Potassium and Its Uptake by Ryegrass
Author(s) -
Mengel Konrad,
Uhlenbecker Karina
Publication year - 1993
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/sssaj1993.03615995005700030023x
Subject(s) - chemistry , potassium , diffusion , extraction (chemistry) , lolium perenne , power function , analytical chemistry (journal) , diffusion equation , soil water , clay minerals , mineralogy , chromatography , soil science , thermodynamics , botany , geology , poaceae , mathematics , physics , organic chemistry , biology , mathematical analysis , economy , economics , service (business)
Nonexchangeable soil K + trapped between interlayers of clay minerals is an important source of K + for plants grown on many soils. The availability of nonexchangeable K + depends primarily on the release rate of K + from the interlayers of clay minerals. The objective of this investigation was to test whether the K + release rate of nonexchangeable K + can be measured with a modified electroultrafiltration (EUF) technique, which essentially involved removal of soil K + from an electrodialysis cell at 20°C for 30 min at 200 V, followed by a second 30‐min extraction at 80°C and 400 V. The experiments were carried out with two Alfisols (Argalfs), one Vertisol (Orthert), and one Entisol (Aquent). The cumulative K + extraction curves obtained with an extraction at 400 V and 80°C were described ( P < 0.01) by the first‐order equation, the parabolic diffusion equation, the power function, and the Elovich equation, with the latter showing the best fit. An important term of these equations is the constant b , which is indicative of the release rate of nonexchangeable K + . The b values obtained by the Elovich function and by the parabolic diffusion equation decreased with the depletion of nonexchangeable K + brought about by the uptake of K + by ryegrass ( Lolium perenne L. cv. Taptoe). Potassium uptake by ryegrass grown in Mitscherlich pots was correlated with the b values of the parabolic diffusion equation, the power function, and particularly the Elovich function. The latter finding shows that the b value represents a reliable indicator for the availability of nonexchangeable K + . The same is true for the NH 4 + ‐exchangeable K + , provided the soil is low in exchangeable K + .