The Influence of Selenium, Salinity, and Boron on Alfalfa Tissue Composition and Yield

Abstract

Abstract Alfalfa ( Medicago sativa L.) was grown in greenhouse sand culture to determine the effects of Se(VI), SO 2− 4 ‐salinity and B on alfalfa tissue composition and yield. A 4 × 2 × 2 factorial experiment was conducted with treatments consisting of four Se concentrations (0, 0.25, 0.5, and 1.0 mg Se(VI) L −1 as Na 2 SeO 4 ), two B concentrations (0.5 and 3.0 mg B L −1 as H 3 BO 3 ), and two salinity levels (0.5 and 5.0 dS m −1 as Na 2 SO 4 and CaSO 4 ·2H 2 O). Three cuttings were made and the vegetative portions analyzed for dry weight and total Se, S, and B. Plant yields were significantly reduced by both salinity and Se(VI) but not by B. Tissue Se concentrations were positively correlated with Se in the irrigation water but negatively correlated with SO 2− 4 ‐salinity and B. Plant Se was reduced from 620 mg Se kg −1 to less than 7 mg Se kg −1 in the presence of SO 2− 4 ‐salinity. A synergistic effect between Se and S was found at the basal nutrient concentration of SO 2− 4 (0.5 m M ). Tissue S was increased from less than 3 g S kg −1 to over 10 g S kg −1 with the addition of 1 mg Se L −1 . Alfalfa can potentially accumulate extremely high concentrations of Se when exposed to soluble Se(VI) in the root zone.