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Agronomy Journal Abstract -

Inoculation and Nitrogen Affect Herbage and Symbiotic Properties of Annual Medicago Species


This article in AJ

  1. Vol. 90 No. 6, p. 781-786
    Received: Nov 1, 1997

    * Corresponding author(s): sheaf001@maroon.tc.umn.edu
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  1. Yanping Zhu,
  2. Craig C. Sheaffer ,
  3. Carroll P. Vance,
  4. Peter H. Graham,
  5. Michael P. Russelle and
  6. C. M. Montealegre
  1. D ep. of Agronomy and Plant Genetics, Univ. of Minnesota, St. Paul, MN 55108
    D ep. of Soil, Water, and Climate Univ. of Minnesota, St. Paul, MN 55108
    U SDA-ARS Univ. of Minnesota, St. Paul, MN 55108



The interactive effects of Sinorhizobium inoculants and soil N status should affect the N contribution of annual medics (Medicago spp.) in cropping systems. We determined the effect of N and commercial medic inoculum on nodulation, dry matter, and N yield of annual medics and also determined Sinorhizobium strain occupancy in annual medic nodules. Field experiments were conducted on a sandy, mixed Udorthentic Haploboroil and on a fine-loamy, mixed, mesic Typic Hapludalf. More than 75% of annual medic plants (except M. rugosa Desr.) were nodulated in the absence of commercial inoculum, and nodulation was due in part to a Sinorhizobium strain that frequently nodulates alfalfa (Medicago sativa L.). Among the five strains in the commercial medic inoculum, 102G3 and 102A13 had the greatest nodule occupancy. When no N was applied, inoculation improved the percentage of plants nodulated and nodule mass only in M. rugosa, compared with no inoculation, but inoculation increased herbage yields of spring-seeded M. truncatula Gaertn. cv. Sephi, M. polymorpha L., and M. rugosa by about 60%, compared with no inoculation. Nitrogen addition reduced the nodule mass of all species when inoculum was applied, and N addition increased only the herbage dry matter yield of spring-seeded M. scutellata (L.) Mill. when inoculum was applied. This suggests that a more effective inoculum could be developed for M. scutellata so that N would not limit herbage growth. Annual medics fixed from 40 to 80 kg N ha−1 if spring-seeded and grown for 60. d, and from 20 to 50 kg N ha−1 if summer-seeded and grown for 43 d.

Published as Minnesota Agric. Exp. Stn. Scientific Journal Series Paper No. 91-1-130040.

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