Remedial Postemergence Legume Inoculation with Rhizobium1
- D. D. Rogers,
- R. D. Warren and
- 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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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