Quality of animal and human life as affected by selenium management of soils and crops

Nutrient management of soils and crops affects the quality of crops with respect to their selenium (Se) and other mineral composition. A number of world regions are deficient in Se to meet the needs of animals and humans. In general, soils containing less than 0.6 mg Se kg(-1) and crops containing less than 0.1 mg kg(-1) are considered deficient for animals and humans. Areas receiving sulfur fertilization contain low Se because sulfur interferes with Se uptake by plants. Principal Se responsive diseases in animals can be divided in. to four groups: Musculoskeletal (white muscle disease and neonatal weakness), reproductive (retained placentae and abortions), gastrointestinal (diarrhea and ill thrift), and immunologic (immune system deficits). Human pathology reflects these animal disease states. Specific immune, reproductive, neurologic, and cardiac disorders are found in humans deficient in Se. Additionally, certain cancers and chronic diseases appear to be related to Se in the human diet. A higher Se status in humans has proven beneficial in specific disease states such as pediatric cardiomyopathy and viral hepatitis. Selenium fertilization of soil, Se application as a foliar spray or seed treatment with Se at 10 g Se ha(-1) applied as selenate results in crops sufficiently enriched with Se, for one year, to protect against Se deficiency. Selcote(R) ultra (CropCare Holdings Ltd., Richmond, New Zealand) at 10 g Se ha(-1) provides a longer residual effect with adequate Se levels in most crops for up to two years. Although there are other methods of overcoming Se deficiency but crop enrichment and consumption of crop products containing Se in organic form is more bio available.