Soil-applied selenium effects on tissue selenium concentrations in cultivated and adventitious grassland and pasture plant species

According to international nutritional standards, plant selenium (Se) concentrations in Belgium are too low. To correct this situation, adding Se in fertilizers for pastures and grasslands is suggested, similar to activities in Finland. However, there is a lack of data on meadow plant species' ability to absorb Se. Therefore, a pot experiment was initiated using 24 meadow plant species cultivated on a Belgian cambisol receiving standard fertilizer treatment, with or without the addition of 9 g Se ha(-1) yr(-1) as sodium selenate. Soil Se analysis confirmed the low Se status of the native soil. Mean foliar Se concentration in the control group was 0.05 mg kg(-1). Because plant deficiency may occur at levels less than 0.10 mg Se kg(-1), data provided further evidence for Se deficiency in Belgium plant production. When grown with Se, plant species showed wide variations for Se concentration, ranging from 0.08 to 0.49 mg Se kg(-1). All values were less than 2 mg Se kg(-1), the suggested threshold toxicity level for dairy cattle. There were two different types of plants in terms of response to Se fertilization. Most of the tested plants were known as nonaccumulators. There were also two probable secondary accumulators: Sinapis arvensis and Melilotus albus. Finally, one has to question the reliability of plant Se enhancement using this method when floristic composition is poorly controlled.