Selenium (Se) is both an essential micronutrient and a toxic environmental pollutant, with a narrow range between dietary adequacy and toxic level. The WHO recommends a daily intake of 50 to 200 μg of Se for adults. The human intake of Se is mainly from food consumption and dependent on the level of Se in the soil in which the plant grows (Rayman 2000). Selenium in plants is controlled by soil bioavailable Se, which is determined by soil total Se and Se speciation.