267-6 Role of Organic Matter On Boron Adsorption-Desorption Hysteresis of Soils.

See more from this Division: S02 Soil Chemistry
See more from this Session: Oxyanion Sorption and Speciation: I
Tuesday, October 23, 2012: 2:15 PM
Duke Energy Convention Center, Room 207, Level 2
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Sabine Goldberg and Donald L. Suarez, USDA-ARS, U.S. Salinity Laboratory, Riverside, CA
In this study we evaluated the boron (B) adsorption/desorption reaction of 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 organic matter content were selected for the study.  Adsorption experiments were carried out to determine B adsorption isotherms using 0.01 M NaCl solutions containing 0 to 100 mg B kg-1.  The soils were equilibrated for 23 hours.  Boron desorption was investigated after replacing aliquots with B-free 0.01 M NaCl solution three times.  Three of the soils were also spiked with 0-100 mg B kg-1 and equilibrated for up to 23 months at field capacity water content in a temperature controlled room at 25oC.  At various intervals subsamples were extracted with DTPA-sorbitol, boiling water, and 0.1 M NaCl.  The B adsorption/desorption behavior of all six soils was found to be nonhysteretic in the short-term experiment, regardless of organic matter content.  Apparent hysteresis of B adsorption can result from difficulties in the experimental procedure itself.  Some B adsorption hysteresis was found for two soils with all three extractants after long-term equilibrations of 1 to 23 months.  Our results do not support the hypothesis that B desorption hysteresis increases in soils with increasing organic matter content.
See more from this Division: S02 Soil Chemistry
See more from this Session: Oxyanion Sorption and Speciation: I