Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2012
Publication Date: 7/1/2012
Publication URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2376.pdf
Citation: Goldberg, S.R., Suarez, D.L. 2012. Role of organic matter on boron adsorption-desorption hysteresis of soils. Soil Science. 177(7):417-423. 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. Release of added boron was quantified on six soils of varying organic matter content. Various extracting solutions were evaluated for their ability to measure boron release after reaction times up to 23 months. We have found that the vast majority of added boron was readily released indicating reversibility of the reaction regardless of organic matter content. 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: In this study we evaluated the boron (B) adsorption/desorption reaction in six soils and examined the extent to which organic matter content, as well as incubation time affected B release. Six soils varying in initial pH, clay content, and were selected for the study. Adsorption experiments were carried out to determine B adsorption isotherms using 0.01 M NaCl solutions containing 0-100 mg B kg-1. The soils were equilibrated for 23 hours. Boron desorption was investigated after replacing 10 mL aliquots with B-free 0.01 M NaCl three times. Three of the soils were also spiked with 0-100 mg B kg-1 and equilibrated up to 23 months at field capacity water content in a temperature controlled room at 25C. At various intervals subsamples were extracted with DTPA-sorbitol, boiling water, and 0.1 M NaCl. The B adsorption/desorption behavior of four soils was found to be nonhysteretic, regardless of organic matter content. The behavior of two soils was slightly hysteretic, likely due to difficulties in the experimental procedure. Our results do not support the hypothesis that B desorption hysteresis increases in soils with increasing organic matter content or decreases with increasing soil pH.