Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2004
Publication Date: 3/1/2004
Citation: Byun, J., Sheaffer, C.C., Russelle, M.P., Ehlke, N.J., Wyse, D.L. 2004. Dinitrogen fixation in Illinois bundleflower. Crop Science. 44:493-500. Interpretive Summary: The search continues for wild plant species that will help us produce food, feed, and fiber across the diverse soils and climates on Earth. A major problem farmers still face is the lack of legumes that are well adapted to grow with warm season grasses, like prairie grasses. Legumes produce high-quality feed and help improve the growth of grasses through a process called symbiotic nitrogen fixation. In this process, certain bacteria living in legume roots obtain nitrogen from the air and give it to the plant. This nitrogen helps the legume produce high-protein leaves and seeds which animals eat. Furthermore, there is usually enough nitrogen to help adjacent grasses grow bigger. We measured, for the first time, how much symbiotic nitrogen fixation occurred with Illinois bundleflower, a native prairie legume in the U.S. The amounts were similar to some other legumes, like white and red clover, and were larger with higher-yielding plants. At one of the locations we tested, it appeared that some plant nutrients were too low, which emphasizes that farmers will need to pay attention to soil fertility for this crop. We also discovered that the plants grew best in a region where they grow wild. This means that there may be better bacteria in the soil in that area or that other microorganisms may be improving plant growth. Our results will help other scientists, like plant breeders and soil scientists, develop better plants and discover bacteria that will make Illinois bundleflower a valuable addition to warm season pastures.
Technical Abstract: Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMillan] is a warm-season perennial forage legume that may serve as a pulse crop. Its productivity is influenced by its N2 fixation capability. Our objective was to estimate symbiotic N2 fixation of three Illinois bundleflower accessions from the north-central U.S. grown in pure stands at three Minnesota locations during the 2 years after seeding. Herbage yield averaged across accessions ranged from 1.0 Mg/ha to 3.7 Mg/ha in yr 1 and from 3.0 Mg/ha to 8.3 Mg/ha in yr 2. Accessions differed in herbage yield, above-ground N yield, and N2 fixed at certain locations in yr 1, but did not differ among locations in yr 2. The fraction of N derived from the atmosphere (fNdfa) varied with location but not with accession in either year. Differences in N2 fixed among accessions in yr 1, therefore, were due to differences in N yield rather than to fNdfa. The 15N natural abundance method gave consistently lower estimates of fNdfa than the 15N enrichment method. In yr 1, N2 fixation estimates ranged from 0 to 30 kg/ha N (15N natural abundance method), 11 to 43 kg/ha (15N enrichment method), and 0 to 50 kg/ha N (total N difference method), and in yr 2 these estimates at two locations were 60 to 67 kg/ha N, 79 to 127 kg/ha N, and 67 to 142 kg/ha N, respectively. No N2 was fixed in yr 2 at the third location, possibly due to adverse weather or to S and/or Mo deficiency. Nodule occupancy by rhizobia may contribute to the observed location differences. One of the two inoculant strains accounted for almost all nodules at two locations, whereas at the high-yielding location, one-half of the nodules were occupied by indigenous rhizobial strains.