Influence of soil solution salinity on boron adsorption by soils

Authors: Goldberg, Sabine; Suarez, Donald; Shouse, Peter

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2008
Publication Date: 6/1/2008
Citation: Goldberg, S.R., Suarez, D.L., Shouse, P.J. 2008. Influence of soil solution salinity on boron adsorption by soils. Soil Science. Vol. 173:368-374.

Interpretive Summary: Boron is a specifically adsorbing anion that can be detrimental to plants at elevated levels. Detrimental levels can occur because of high levels of boron in the soil solution or from additions of boron via the irrigation water. Adsorption of boron by two soils was evaluated as a function of equilibrium solution boron concentration, solution pH, and electrolyte concentration and predicted using a chemical model and easily measured soil chemical characteristics. Our results will benefit scientists who are developing models of boron movement in arid zone soils. The results can be used to improve predictions of boron behavior in soils and thus aid action and regulatory agencies in the management of soils and waters which contain elevated concentrations of boron.

Technical Abstract: Boron adsorption on two arid-zone soils from the San Joaquin Valley of California was investigated as a function of equilibrium solution B concentration (0-250 mg L-1), solution pH (3-12), and electrical conductivity (EC = 0.3 or 7.8 dS m-1). Boron adsorption on both soils increased with increasing pH, reached a maximum near pH 9, and decreased with further increases in pH. Boron adsorption as a function of solution pH was independent of solution salinity from pH 3 to 9. Above pH 9, B adsorption was increased from the solution of higher EC. Boron adsorption for both soils as a function of solution B concentration conformed to the Langmuir adsorption isotherm equation. The B adsorption maxima obtained with the Langmuir equation for both ECs were not statistically significantly different at the 95% level of confidence. The constant capacitance model, a surface complexation model, was able to describe B adsorption as a function of solution B concentration and solution pH. Boron adsorption was predicted using the soil chemical properties: surface area, organic carbon content, inorganic carbon content, and aluminum oxide content. The predictions are suitable for transport modeling and will be used to describe B movement in large soil columns. Our results are advantageous, as they indicate that under agricultural conditions, B adsorption can be described without consideration of changes in soil solution salinity.