EFFECT OF FOLIAR-APPLIED SELENIUM ON YIELDS AND SELENIUM CONCENTRATION OF ALFALFA, TIMOTHY AND BARLEY

Abstract

In a field study, the residual effects of 1, 2, and 4 kg Se/ha applied as a foliar spray and of 1 kg Se/ha applied to the soil were measured for up to five cropping seasons on yields and Se concentration of alfalfa (Medicago sativa L.), timothy (Phleum pratense L. and barley (Hordeum vulgare L.). Selenium applied as foliar spray reduced yields by 16–37% for the three species in the first year but had no effect in the second and subsequent years. Foliar applications of Se at 1–4 kg/ha in the first year produced alfalfa and timothy containing 27–142 ppm Se, which, when fed to livestock, would cause Se toxicity. Barley grain at these rates contained 4.3–8.4 ppm Se. The tissue Se concentrations of the three species did not exceed 0.6 ppm in the second and subsequent years. The residual effect of 1 kg Se/ha applied to the soil lasted longer on the three species than 1 kg Se/ha applied as foliar spray. Selenium applied to soil or as a foliar spray at 1 kg/ha resulted in tissue concentrations greater than 0.1 ppm Se in forages for two to four cropping seasons, and in barley grain for one to two cropping seasons. At 2 and 4 kg Se/ha, applied as a foliar spray, the tissue Se levels greater than 0.1 ppm were maintained for two to four cropping seasons in barley, alfalfa, and timothy. Tissue Se concentrations were generally higher in timothy than in alfalfa and barley grain. Key words: Forages, barley, selenium, yields, foliar application, podzol soil