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Exchangeable Potassium as Affected by Mica Specific Surface in Some Soils of North Central United States
Author(s) -
Milford M. H.,
Jackson M. L.
Publication year - 1966
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/sssaj1966.03615995003000060023x
Subject(s) - mica , loam , soil water , subsoil , mineralogy , weathering , geology , potassium , silt , chemistry , soil science , geochemistry , geomorphology , paleontology , organic chemistry
Mineralogical analyses of samples from 16 surface soil horizons and 9 subsoil horizons, representing 15 soil series, revealed that differences in the content of clay sized mica were closely related to the wide differences in the content of exchangeable K in ovendried samples before and after cropping. The specific surface of mica in the clay fraction was significantly correlated with the content of exchangeable K in oven‐dried samples before cropping ( r = 0.63), after cropping ( r = 0.74), and after fertilization and cropping ( r = 0.68). After being cropped and oven dried, for example, a sample of Wabash silt loam surface soil contained 466 pp2m exchangeable K, but a sample of Bates silt loam surface soil contained only 78 pp2m exchangeable K. These samples had 3.3 m 2 /g and 0.5 m 2 /g, respectively, of mica specific surface area. No significant relationship occurred between the content of exchangeable K in field moist samples and the content of mica in the soils. The wedge‐zone concept of mica weathering in crystal edges and in crystallographic (hk0) fractures normal to (001) crystal faces was used to explain the relationships between specific surface of mica and content of exchangeable K in oven‐dried samples. The existence of an equilibrium between exchangeable K in the open part of the wedge with nonexchangeable K at the mica weathering side of the wedge was indicated.