INFLUENCE OF ACIDITY AND POTASSIUM SATURATION ON PLANT UPTAKE OF INDIGENOUS SOIL RUBIDIUM

Rubidium is frequently used as a tracer of K+ in plants and soils. How ever, uptake of Rb+ from Soils by plants, fungi, and even animals is g reatly influenced by soil properties. Field biomass concentrations of Rb+ usually vary by one-two orders of magnitude, largely according to soil acidity. A growth experiment was conducted using a sedge, Carer p ilulifera, transplanted in 50 natural and semi-natural unfertilized so ils representing a wide range of chemical properties. It is suggested that pH-dependent reactions regulating the Rb+ solubility in soils and an increased plant uptake of Rb+, when K+ is deficient, are major con ditions accounting for differences in plant uptake of Rb+ from contras ting soils. The pool size of exchangeable, indigenous soil Rb+, within the ranges usually encountered, seems to be of less importance. (C) 1 997 Elsevier Science B.V.