Growth of Three Native Prairie Perennials as Influenced by Phosphorus Fertilization, Potting Media, and Mycorrhizae

Abstract

Abstract Seedlings of blue wildindigo [Baptisia australis (L.) R. Br.], rough gayfeather (Liatris aspera Michx.), and butterfly milkweed (Asclepias tuberosa L.) were grown in either a 1 soil : 1 sphagnum peat : 1 perlite (by volume) or 1 soil : 1 sand medium (v/v), amended with 0.00, 0.29, or 0.58 kg P/m3, and inoculated with Glomus etunicatum Becker and Gerd., G. fasciculatum (Thax. sensu Gerd.) Gerd. and Trappe, G. macrocarpum Tul. and Tul., G. mosseae (Nicol. and Gerd.) Gerd. and Trappe, or remained noninoculated. The objective was to determine whether vesicular-arbuscular mycorrhizal (VAM) fungi can establish and enhance plant growth, and how this would be affected by soil amendments. Replications were transplanted into the field to determine whether VAM pretransplant inoculation increased host growth and flowering. In the greenhouse, total dry weight of the three wildflower species grown in 1 soil : 1 sand (v/v) medium with no P was significantly improved by addition of most mycorrhizal species tested, but the response varied among plant species. At 0.29 kg P/m3, fewer mycorrhizal growth responses were evident. No growth responses were evident at 0.58 kg P/m3. B. australis was the only species that benefited from mycorrhizal inoculation in the 1 soil: 1 sphagnum peat: 1 perlite (by volume) medium at 0.00 and 0.29 kg P/m3. There were no differences in tissue P content within the three species when VAM-inoculated plants at 0.00 kg P/m3 were compared to noninoculated controls. At 0.29 kg P/m3 in the 1 soil : 1 sand medium, inoculated seedling tissue P increased, but in the 1 soil : 1 sphagnum peat : 1 perlite medium, noninoculated controls had significantly higher tissue P contents compared to inoculated seedlings. In the field, height and inflorescences per plant for the wildflowers were improved by VAM inoculation during the 2nd growing season.