Assessment of potassium in soils

Publisher Website
Google Scholar
Abstract
K in soils from selected plots of the Broadbalk Experiment at Rothamsted, and Rotation I experiment at Saxmundham, UK was measured by 5 methods: the boiling nitric acid extractions of Haylock and Maclean, electro-ultrafiltration, release to Ca-saturated ion exchange resin and a new procedure using extraction by HC1 under reflux. All the methods showed clearly the differences between the 2 soil types, and between the differently fertilized plots on the basis of amounts, and in some case rates of release, of different categories of soil K (exchangeable, fixed and native). The quantity of exhangeable K measured by each method, except that by Ca-resin, gave significant correlations with the K balance of the soils, and yield and/or K offtake of winter wheat grown on the plots. The new HCl-reflux method gave the closest correlations. The amount and rate of release of fixed (available but not exchangeable) K estimated by HCl-reflux was also correlated with yield and offtake.