Retention and Uptake by Plants of Added Selenium in Peat Soils

Abstract

In soil, adsorption of selenium (Se) onto mineral surfaces is accompanied by poorly known retention via organic matter. The effects of these components on the availability of Se were examined in two pot experiments. Spring wheat was grown with increasing amounts of selenate (SeO₄ ^2–) in one sand and three peat soils, and ryegrass with selenate and selenite (SeO₃ ^2–) in sphagnum peat manipulated by iron (Fe) hydroxide. Selenate persisted in soluble form, whereas selenite was fixed in the soil. In wheat, 5–50% of the selenate addition was recovered in the plant, the proportion increasing with increasing Se. In ryegrass, 30–40% of the added selenate but less than 2% of the selenite was found within the leaves. The Fe hydroxide enrichment enhanced the selenite uptake. Phosphate buffer desorbed a minor proportion of the added selenite, except in peat amply enriched with Fe hydroxide. The results suggest that the retention mechanism of selenite was changed due to the hydroxide amendment.

Keywords:

• Adsorption
• fertilization
• selenate
• selenite
• selenium
• plant uptake

Acknowledgments

We thank Antti Jaakkola, Jaakkola Farm, for providing us the peat soils of experiment 1 and Marja Turakainen, Laura Pulli, Mari Räty, and Maija Ylinen for excellent assistance in the greenhouse and/or with the laboratory analyses. For funding of this study, we are grateful to the Finnish Ministry of Agriculture and Forestry, Suoviljelysyhdistys ry, and the Finnish Cultural Foundation.