Evaluation of different plant species used for phytoremediation of high soil selenium

Concentrations of selenium (Se) in agricultural irrigation effluent increased stored soil Se to toxic levels in the wetland sediment at Kesterson Reservoir. Vegetation management (phytoremediation) may be a strategy to reduce these soil Se concentrations to nontoxic levels. Selenium in plant shoots and depletion of soil Se removal by selected plant species were evaluated over a l-yr period under greenhouse conditions. Two soils were used: a seleniferous Turlock soil (collected from Kesterson Reservoir) that contained high total Se (similar to 40 mg kg(-1) soil), high water extractable B (similar to 10 mg B L-1), and a soil salinity of similar to 8 dS m(-1), and a nonseleniferous Hanford sandy loam (collected from an agricultural field site). Three plant species tested were Brassica napus cv. Westar (canola), Hibiscus cannabinus L. cv. Indian (kenaf), and Festuca arundinacea Schreb. cv. Alfa (tall fescue). Only canola and kenaf grown in Turlock soil showed significant lower shoot yield (P < 0.01) than on the Hanford soil. Leaf Se was as high as 470 mg Se kg(-1) DM in canola, 45 mg Se kg(-1) DM in kenaf and 50 mg Se kg(-1) DM in tall fescue. The same crops contained mean leaf B concentrations as high as 415 mg B kg(-1) DM in kenaf, 180 mg B kg(-1) DM in canola, and 111 mg B kg(-1) DM in first clipping of tall fescue. The cultivation of all species led to a significant reduction (P < 0.01) of total soil Se between preplant and the final harvest by the following percentages: canola (47%), kenaf (23%), and tall fescue (21%). Successively planting of canola and to a lesser extent kenaf and tab fescue, in Se-laden soil has the potential to reduce fetal soil Se.