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Potassium Availability in Nason Soil as Influenced by Ammonium and Lime
Author(s) -
Murdock L. W.,
Rich C. I.
Publication year - 1965
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/sssaj1965.03615995002900060032x
Subject(s) - vermiculite , lime , chemistry , potassium , loam , ammonium , cation exchange capacity , ion , soil water , soil ph , environmental chemistry , inorganic chemistry , agronomy , soil science , horticulture , geology , paleontology , organic chemistry , biology
A greenhouse experiment was established to find if NH 4 + increases K + availability when Nason silt loam is limed to pH 7.0 as suggested by previous laboratory studies. Two oat crops were grown in soil at 3 lime levels (1, 5, and 15 g/1,000 g), 2 K levels (0 and 0.5 meq/100 g) and 2 N sources [Mg(NO 3 ) 2 and NH 4 NO 3 ]. At high soil pH, potassium uptake was significantly greater where the N source was NH 4 NO 3 as compared to Mg(NO 3 ) 2 . The results support soil extraction data which show that at about pH 7.0, NH 4 + ions are considerably more efficient in displacing K + from this soil than are Mg 2+ ions. It is concluded that the smaller NH 4 + ions are able to penetrate to exchange positions not accessible to large hydrated Mg 2+ ions. The results do not support an explanation of the differential K uptake based on the antagonistic effect of Mg 2+ ions on K + nor due to an effect caused by lower soil pH with NH 4 NO 3 fertilization. Although K fixation occurs at high pH in this soil, this fixation does not appear to be associated with greater collapse of expansible vermiculite. In fact, it is shown that liming caused the vermiculite to be less subject to collapse on K saturation. The reason for the greater fixation at high pH may be that there is less competition for the specific sites by H 3 O + ions and thus greater opportunity for selection of K + ions which are of similar size.