HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bolt, G. H. Articles by Kamphorst, A. Search for Related Content PubMed Articles by Bolt, G. H. Articles by Kamphorst, A. Agricola Articles by Bolt, G. H. Articles by Kamphorst, A.

A Study of the Equilibria Between Three Categories of Potassium in an Illitic Soil¹

ABSTRACT

The release of K from K-Ca-illites by repeated extraction with 0.5 N solutions of various salts was determined. From comparison between the action of NH₄ ions and Na ions it could be deduced that the rapidly exchangeable K occupies two types of sites, which were named "planar" sites and "edge-interlattice" sites, respectively. The very high preference for K of the edge-interlattice sites explains why, e.g., Na ions and Ca ions are very ineffective in removing K from these sites as long as the released K ions are not removed from the system. NH₄ ions are, in contrast, highly competitive for the edge-interlattice sites, but their action is kept within bounds by the fact that the mineral lattice remains fairly well closed during the penetration of NH₄ ions. An analysis of the exchange curve against Na ions yielded an estimate of the distribution and properties of the different types of sites, viz about 500 µeq. per g. rapidly exchangeable sites, of which 96% is situated on the external planar side of the lattice (preference factor for K about 2 in comparison to Ca ions), and 4% is located on the edges (preference factor for K about 500 in comparison to Na ions). In addition to this the illite studied contained about 700 µeq. K per g. in interlattice positions, which will lead to a very slow release of K if the chemical potential of K in solution is maintained at a low level.

¹ Contribution from the Laboratory of Soils and Fertilizers, State Agricultural University, Wageningen, Neth.

² Professor of Soil Science, State Agricultural University, Wageningen; Senior Lecturer in Soil Science, University of Natal, Pietermaritzburg, South Africa; and Research Student, State Agricultural University, Wageningen, respectively.

Received for publication July 30, 1962. Accepted for publication November 7, 1962.