Increasing selenium in field-grown onions by planting in peat moss pots containing coal fly ash

Selenium is an essential element for animals and humans and is deficient in soils in the Northeastern United States. Coal fly ash added to soils has been shown to serve as a source of selenium for absorption by plants. It was of interest to study the uptake of selenium by plants if coal fly ash was added to peat moss pots in which the plants were grown prior to transfer of the potted plants to the field. Onions were grown in peat moss pots containing a vermiculite-spaghnum peat mono mixture to which were added increasing (10, 25 and 50) weight percentages of fly ash. After transfer of the pots to a field soil, the harvested onion bulbs were freeze-dried and analyzed for selenium. Whereas there were no significant differences in the concentrations of selenium in onions grown in the media containing 0 (control), 10 or 25% fly ash, those grown in the media containing 50% fly ash were significantly higher (p < 0.001). The agricultural implications of these findings are discussed.