LAUSR

Abstract Selenium (Se) is indispensable for animals and humans. One option to address Se deficiency is to biofortify plants with Se. Biofortification of forage with Se nanoparticles (NPs) is gaining more attention as an efficient and safe source of Se for livestock. The purpose of this study was to investigate the effect of different concentrations of NPs-Se (0, 30, 50, 100, 150, and 250 mg·L−1) on the growth of alfalfa harvested multiple times, and to provide a basis for the production of Se-enriched forages. Applying 50 mg·L−1 concentration of NPs-Se had the best effect on yield over three harvests. Over three harvests, low-dose NPs-Se (30 and 50 mg·L−1) application significantly increased peroxidase and superoxide dismutase activities, chlorophyll content and carotenoid content, and significantly decreased malondialdehyde content. The total Se content and Se accumulation in plants at the same harvest showed an upward trend with increasing Se concentration. At the same concentration, from first harvest to third harvest, Se content and Se accumulation showed an initially increasing and then decreasing trend. The evaluation found that foliar application of NPs-Se at 50 mg·L−1 could have the greatest positive effect on the growth and yield of multiple-harvested alfalfa.