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This article in AJ

  1. Vol. 74 No. 4, p. 613-619
    Received: Sept 18, 1981

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Remedial Postemergence Legume Inoculation with Rhizobium1

  1. D. D. Rogers,
  2. R. D. Warren Jr. and
  3. D. S. Chamblee2



Legume inoculation failures often result in severe stand losses and yield reductions. The objective of this study was to determine the possibility of salvaging poorly nodulated stands of fall-seeded ‘Arc’ alfalfa (Medicago sativa L.) (fine-loamy, siliceous, thermic Typic Paleudult soil type) and ‘Viking’ birdsfoot trefoil (Lotus corniculatus L.) (clayey, kaolinitic, thermic Typic Hapludult soil type). Three postemergence soil inoculation techniques were evaluated in the field: a) Subsurface application of inoculum-coated sand, b) subsurface application of a peat-base granular inoculant, and c) application of a water-inoculum suspension as a surface spray. Varying rates of the appropriate Rhizobium strains (Rhizobium meliloti Dang., or Rhizobium sp. of Lotus subgroup) were applied approximately 2, 4, or 8 weeks after seedling emergence. Measurements of nodulation, N concentration, and yield were made.

Satisfactory nodulation and plant growth were generally obtained from inoculation treatments made 2 and 4 weeks after plant emergence with all three techniques. Remedial inoculation treatments made in late fall approximately 8 weeks after plant emergence were unsuccessful. Except under low moisture conditions, inoculum application rates ranging from 1.4 to 1.9 kg/ha were sufficient for effective nodulation for techniques a and c. The lowest rates tested for technique b ranged from 4.5 to 6.8 kg/ha and were also satisfactory. Average first alfalfa harvest yields (two experiments) following subsurface application of 1.6 kg/ha of inoculum with a sand carrier were 2,900, 2,750, 970, and 360 kg/ha for the 2, 4, 8-week, and noninoculated treatments, respectively. With sufficient moisture availability, higher yields resulted from seed inoculation than from postemergence inoculation; however, those differences had largely disappeared by the third harvest. When applied as a surface spray under favorable environmental conditions, application of 1.4 kg/ha of peat-base inoculum in 187 liters/ha of water produced first harvest alfalfa yields of 4,305, 3,985, 520, and 200 kg/ha for the 2, 4, 8-week, and noninoculated treatments, respectively.

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