Uptake and accumulation of selenium by terrestrial plants growing on a coal fly ash landfill. Part 2. Forage and root crops

Plants grown on fly ash landfills can accumulate relatively high concentrations of selenium (Se), although concentrations can vary greatly among and within species. We examined the accumulation of Se in forage and root crops grown on a fly ash landfill and nonlandfill sites and the relationship of soil Se to plant Se concentrations. Because sulfur (S) can act as a competitive ion with Se in plant uptake of nutrients, gypsum (CaSO₄.2H₂O) was applied to soil on a fly ash landfill to determine whether Se was reduced in plants in its presence. Slightly more Se was accumulated in plants grown on the landfill than on the nonlandfill site. Total Se concentration in soil was poorly correlated with Se concentration in alfalfa plants grown on the landfill. In alfalfa (Medicago sativa L.), oats (Avena sativa L.), and rutabaga (Brassica napus L.), application of gypsum at rates of 5.6 to 16.8 t ha⁻¹ reduced the uptake of Se from that of plants grown without gypsum. Results from this study indicate that gypsum amendment may be effective in decreasing the uptake of Se by plants growing on a fly ash landfill, but the response is quite variable, probably due to variability in concentration and availability of Se in the soil cap. The use of gypsum in limiting Se uptake by plants offers a possible management tool to control the cycling of Se through plants to other biota on fly ash landfills.