Leaching of Added Selenium From Alkaline Soils as Influenced by Sulfate

A BaSO 4 ‐BaSeO 4 mixture (S:Se = 10) and BaSeO 4 alone were applied at 1.60 and 3.20 mg Se per column to two soils and leached with water or gypsum solution. Eight hundred milliliters (10‐cm depth) of leaching solution were added to columns containing 2,100 g of Portneuf silt loam and 2,500 g of Gooding loamy sand at 4‐week intervals for 20 weeks. More Se was leached by gypsum solution than by water from all columns. Where 1.60 mg Se per column was applied, more Se was leached from Gooding loamy sand than from Portneuf silt loam soil with both water and gypsum solution. Where 3.20 mg Se per column was applied, more Se was leached by water from Gooding than from Portneuf soil, but the reverse was true with gypsum solution. The Se leached from the Portneuf soil treated with the BaSO 4 ‐BaSeO 4 mixture ranged from 0.34 mg, where 1.60 mg Se per column was applied and soils leached with water, to 2.32 mg, where 3.20 mg Se per column was applied and soils leached with gypsum solution. Much less Se was leached where only BaSeO 4 was applied to Portneuf soil. The amount leached ranged from 0.07 mg, where 1.60 mg Se was applied and water used for leaching, to 0.64 mg Se, where 3.20 mg Se was applied and gypsum used for leaching. The Se recovery from the Gooding soil was within these ranges for the same treatments. The Se leached increased with application rate, but not proportionately. The data indicate that addition of SO 4 2‐ increases the solubility of BaSeO 4 in these soils.