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Title: Release of native and amended boron from arid zone soils after varying incubation times

Author
item Goldberg, Sabine
item Suarez, Donald

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2011
Publication Date: 5/1/2011
Citation: Goldberg, S.R., Suarez, D.L. 2011. Release of native and amended boron from arid zone soils after varying incubation times. Soil Science. 176(5):213-217.

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 native and added B was quantified on five arid zone soils. Various extracting solutions were evaluated for their ability to measure B release. Boron release decreased as a function of time for at least some of the extractions and treatments for all five soils. This is consistent with literature that added B becomes less extractable with increased incubation time. 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) release from soils containing elevated native B and examined the extent to which incubation time affected B release. Five soils varying in initial pH and clay content were selected for the study. The soils were spiked with five varying doses of B as H3BO3 (0-100 mg B/kg) and equilibrated for a total of five months at field capacity water content. The soils were incubated in a temperature controlled room at 25oC. At monthly intervals, the soils were thoroughly mixed and subsamples removed. The subsamples were extracted with DTPA-sorbitol, boiling hot water, and 0.1 M NaCl to provide various B extraction protocols. Boron desorption decreased as a function of time for at least some of the extractions and treatments for all five soils. This is consistent with literature that added B becomes less extractable with increased incubation time. Comparison between the three extractants revealed no statistically significant difference in amounts of adsorbed B for three of the soils. For the two others the order of desorbed B amount was: hot-water-soluble < 0.1 M NaCl extractable < DTPA-sorbitol extractable. The decrease in B release appears to be approaching zero for all five soils for most of the extractant solutions. This indicates that a five month incubation is adequate to obtain an accurate assessment of the amount of B available for release. Since the decrease in extractable B with time is not large (except for one soil), a very good indication of extractable soil B can be obtained from a one month incubation study.