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Agronomy Journal Abstract - FORAGES

Dinitrogen Fixation in Kura Clover and Birdsfoot Trefoil


This article in AJ

  1. Vol. 92 No. 6, p. 1216-1220
    Received: Feb 7, 2000

    * Corresponding author(s): russelle@soils.umn.edu
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  1. Philippe Seguina,
  2. Michael P. Russelle *b,
  3. Craig C. Sheaffera,
  4. Nancy J. Ehlkea and
  5. Peter H. Grahamc
  1. a Dep. of Agron. and Plant Genet., Univ. of Minnesota, 1991 Buford Circle, 411 Borlaug Hall, St. Paul, MN 55108-6026 USA
    b USDA-ARS, US Dairy Forage Res. Cent. (Minnesota cluster) and Dep. of Soil, Water, and Climate, Univ. of Minnesota, 1991 Buford Circle, 439 Borlaug Hall, St. Paul, MN 55108-6028 USA
    c Dep. of Soil, Water, and Climate, Univ. of Minnesotam, St. Paul, MN USA


The quantification of symbiotic N2 fixation by legumes is essential to determine their impact on N budgets. Kura clover (Trifolium ambiguum M.B.) and birdsfoot trefoil (Lotus corniculatus L.) are two promising pasture legumes for which such estimates are scarce. Dinitrogen fixation by 2- and 3-yr-old stands of these species was determined at two locations in Minnesota using the 15N isotope dilution method. Species were evaluated for forage and N yields, the percent of N derived from the atmosphere (%Ndfa), and the amount of fixed N2 at each of four harvests. The results for each parameter varied with location, legume species, and harvest, as demonstrated by a three-way interaction among these terms. Across environments, both species produced the greatest amount of forage, total N, and fixed N yields at the first harvest. The yields decreased with successive forage harvests at one location but stabilized at the other. The %Ndfa for Kura clover was stable across harvests and environments. The %Ndfa for birdsfoot trefoil varied during the season, with a peak at the end of the season. The yearly total forage, total N, and fixed N yields of Kura clover were stable across environments, and the total N and fixed N yields were greater than those of birdsfoot trefoil at one location. Overall, Kura clover fixed about 155 kg N ha−1 yr−1, with a %Ndfa of 57; birdsfoot trefoil had amounts of fixed N2 that varied with locations (avg. of 145 kg N ha−1 yr−1), and it obtained about 62% of its herbage N from fixation.

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