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Soil structure and potassium supply. I. The release of potassium from soil aggregates to Ca‐resin
Author(s) -
HEMING S. D.,
ROWELL D. L.
Publication year - 1985
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1985.tb00312.x
Subject(s) - potassium , chemistry , tortuosity , leaching (pedology) , diffusion , soil water , desorption , analytical chemistry (journal) , chromatography , porosity , soil science , thermodynamics , geology , adsorption , physics , organic chemistry
SUMMARY Potassium release from saturated spherical aggregates of three clay soils to Ca‐resin was measured and compared with release in suspensions (Talibudeen et al. , 1978). The diffusion coefficient for K was calculated from measurements of the tortuosity factor using 36 Cl, volumetric water content and buffer power. Release of K is in the order: suspensions >2–3 mm > 6–8 mm aggregates. A computer model incorporating diffusion analysis and release of K shows that in the aggregates the rapidly diffusing exchangeable K, K ex , is best measured by the extrapolated intercept of a desorption isotherm (24 h equilibration), and is 8–55% less than that extracted by NH 4 OAc leaching. Release of K within the aggregates (K nex , a fraction approximating to Talibudeen's peripheral K) is delayed until after about 95% of K ex has been depleted which takes 1–2 days. The effective release rate of K nex inside the aggregates is ∼ 17% less than in soil suspensions. Diffusion imposes only small limitations on the release from aggregates of K nex . This rate of release depends on the frequency of resin changes.