© 1991 Heron Publishing—Victoria, Canada
Consequences of rhizosphere acidification on delivery and uptake kinetics of soil phosphorus
Andrew R. Gillespie and Phillip E. Pope
Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA / Received November 8, 1989
Summary
Experiments were undertaken to quantify the mechanisms by which acidity might affect phosphorus movement and uptake by black
locust (Robinia pseudoacacia L.). Phosphorus diffusion rates in six forest soils were determined by desorption-isotherm buffer power assays. Changes in
diffusion as a function of acidity were measured using pH-adjusted desorption solutions. Depending on soil type and phosphorus
source solubility, up to a fivefold increase in phosphorus diffusion rate was observed with an increased acidity of one pH
unit.
Phosphorus uptake rates of mycorrhizal and non-mycorrhizal black locust at pH 4 and pH 7 were determined from 32P-labeled nutrient-depletion experiments. In mycorrhizal plants, the rate of phosphorus uptake at pH 4.0 was twice that observed
at pH 7.0. Non-mycorrhizal plant uptake rates were similar at both pH 4.0 and pH 7.0.
The contribution of soil nutrient supply mechanisms to plant nutrient content increased with rhizosphere acidification. Uptake
kinetics were also affected by rhizosphere acidification, but to a lesser extent.
