Selenium uptake by plants from soils amended with inorganic and organic materials

Depending on its concentration and chemical form, Se functions as an essential element or potential toxicant to humans, livestock, and waterfowl. Application of seleniferous organic materials to soils may increase plant-available Se content and pose health hazards. This study assessed Se uptake by two successive plantings of canola (Brassica napus cv. Westar) and multiple clippings of tall fescue (Festuca arundinacea L. cv. Fawn) grown in soils [Hanford sandy loam (coarse-loamy, mixed, thermic Typic Durixeralfs) and Panoche clay loam (fine-loamy, mixed, superactive, thermic Typic Torriorthents)] amended with 1.5 mg Se kg(-1) soil as inorganic selenate (Se O-4(2-)) or seleniferous organic materials [alfalfa (Medicago sativa L.), Astragalus praelongus, or cattle (Bos tauris) manure] under growth chamber conditions. Tissues of canola and tall fescue accumulated much greater concentrations of Se from the inorganic SeO42- treatment compared to the treatments with seleniferous organic materials. The addition of crop residue or animal manure to the SeO42--treated soils considerably reduced Se accumulation by both plant species. In soils amended with seleniferous organic materials, more than 80% of the Se remained in soils after two plantings of canola and all clippings of tall fescue. The slow release of plant-available Se in soils amended,vith seleniferous organic materials suggests the use of these materials to control the concentrations of Se in crops grown on nonseleniferous soils.