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Title: Distinguishing boron desorption from mineral dissolution in arid-zone soils

Author
item Goldberg, Sabine
item Suarez, Donald

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2011
Publication Date: 6/22/2011
Citation: Goldberg, S.R., Suarez, D.L. 2011. Distinguishing boron desorption from mineral dissolution in arid-zone soils. Soil Science Society of America Journal. 75(4)1317-1323.

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 adsorbed B was quantified on six arid zone soils. Various extracting solutions were evaluated for their ability to measure native adsorbed B. We were able to distinguish B desorption from B release due to mineral dissolution. 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 release from six arid-zone soils from the San Joaquin Valley of California was investigated as a function of reaction time, solution pH, and suspension density. A multiple batch extraction experiment was carried out for 362 days to distinguish B desorption from mineral dissolution. Amounts of B released decreased rapidly and reached a low constant value after about six months of reaction time. Slopes of the B release curves for the last eight extractions approached zero indicating that this B release was from mineral dissolution. Various B soil tests were evaluated for their ability to measure native adsorbed B. The DTPA-sorbitol extract was the best measure of plant available native B but still only extracted 48% of the amount of B desorbed in the long-term experiment. The greatest amount of B was extracted at the lowest suspension density for DTPA-sorbitol (92 %) and phosphate buffer pH 6.6 (95 %). These extractants are recommended for quantifying native adsorbed B which must be considered in application of chemical speciation transport model such as UNSATCHEM (Suarez and Simunek, 1997) to describing B movement in soils. Incorporation of our results will allow improved predictions of soil solution B concentrations under diverse agricultural and environmental conditions.