Effect of ionic strength and solution pH on P extractability and leaching in coarse-textured soils

• Published in: Canadian journal of soil science 1985-01, Vol.65 (1), p.101-108
• Main Authors: Evans, A. Jr, Sorensen, R.C
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; ions; leaching; Mineral components. Ionic and exchange properties; phosphorus; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; soil pH; Soil science; soil texture; Water and solute dynamics
• ISSN: 0008-4271; 1918-1841
• DOI: 10.4141/cjss85-011

A laboratory study was conducted using columns of Valentine loamy sand to determine the effect of ionic strength (I) and solution pH of a leaching solution on P distribution and extractability with depth. Solutions of KCl at concentrations of 1.0, 10 −2 , 10 −4 and 10 −6  mol∙L −1 with a pH of either 4.0, 6.0, or 8.0 were added to the column after the application of 0.3 g diammonium phosphate to the surface of each column. Approximately two pore volumes, 500 mL of solution, were added to the columns, after which they were sectioned and the amount of Bray extractable P in each section was measured. Increasing I resulted in an increase in the total amount of Bray extractable P per column while extractable P increased with column depth for decreasing I. The pH of the leaching solution did not influence the total amount of Bray extractable P per column, but appeared to influence P distribution for the I = 10 −2 treatment. Dissolved organic carbon in the leachate was found to increase with decreasing I. Changes in the distribution of extractable P with depth were attributed to increased competition for P adsorption sites by various organic molecules, which were released into the bulk solution when the organic matter coatings underwent a transition from the spherocolloid to the linear flexible molecule configuration. Key words: Ionic strength, P movement, organic matter coatings, spherocolloid, anion competition