Potassium Uptake by Cation-Exchange Resins from Soils and Minerals

Abstract

THE use of cation-exchange resins for the extraction of soil potassium shows promise of being of value in soil fertility studies^1–4. Wiklander¹ has discussed the factors which determine the equilibrium distribution of ions between two cation-exchange materials in contact with the same solution. However, the approach to the subject remains empirical because of lack of information on the activity of ions adsorbed on exchanger surfaces. The results with resins in Tables 1 and 2 were obtained by using sufficiently wide ratios of resin to soil or mineral to ensure that practically all the labile potassium was associated with the resin. The potassium analysis was done on the resins (> 60 mesh), which were isolated on a stainless steel sieve (60 mesh) by washing free from finely divided soil or mineral with a jet of distilled water. The washed resin was leached with N ammonium acetate and potassium determined in the leachate using an EEL flame-photometer. (Ammonium-exchangeable potassium is defined as that potassium in soil or mineral which is replaced by the ammonium ion during leaching with an excess of neutral N ammonium acetate.)