Tuesday, November 6, 2007
231-33

Soil Sulfur Amendments to Waste Shale Sites Suppress Plant Selenium Uptake.

Cheryl Mackowiak, University of Florida - Agricultural Research Center, North Florida Research and Education Center, 155 Research Rd., Qunicy, FL 32351 and Michael Amacher, USDA-FS (Forest Service), 1888 N 1700 E, North Logan, UT 84341.

Phosphate ore mining on Southeast Idaho public lands has resulted in numerous waste shale dumps revegetated with forages to stabilize the dumps and support grazing. Alfalfa (Medicago sativa L.), smooth brome (Bromus inermis Leyss.), and western wheat grass (Pascopyrum smithii (Rydb.) A. Löve) are the dominant forage species on these lands. The waste shale contains high concentrations of total and plant available selenium (Se), which may pose a health risk to grazing animals. To demonstrate the feasibility of using sulfur (S) as a soil amendment to restrict Se uptake, 3 kg pots containing 50:50 w/w soil and waste shale were uniformly mixed with 0, 0.5, 1.0, or 2.0 Mg ha-1 S as either elemental S or gypsum. Pots were seeded with alfalfa or western wheat grass. Dry mass and tissue Se were monitored over one growing season (several clippings). Soils were sampled at the conclusion of the study and analyzed for water-soluble, oxalate-extractable, and total-recoverable Se. Sulfur amendments as either elemental S or gypsum at 1.0 Mg ha-1 or greater equally suppressed Se uptake by nearly 50% in both forage species. Alfalfa accumulated more Se than western wheat grass. Recent field studies have shown that surface applied sulfur suppressed Se uptake, as well. Sulfur applications to the soil surface may be a cost effective means for suppressing Se uptake in vegetation found on existing waste shale dumps in Southeast Idaho.