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Agronomy Journal Abstract -

Evaluation of Switchgrass Rhizosphere Microflora for Enhancing Seedling Yield and Nutrient Uptake


This article in AJ

  1. Vol. 90 No. 6, p. 753-758
    Received: June 19, 1997

    * Corresponding author(s): brejda@nstl.gov
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  1. John J. Brejda ,
  2. Lowell E. Moser and
  3. Kenneth P. Vogel
  1. U SDA-NRCS, Soil Quality Inst., 2150 Pammel Dr., Ames, IA 50011
    D ep. of Agron., Univ. of Nebraska, 279 Plant Sci., P.O. Box 830915, Lincoln, NE 68583-0915
    U SDA-ARS, 344 Keim Hall, Univ. of Nebraska, Lincoln, NE 68583-0915



Many rhizosphere microorganisms enhance nutrient uptake and plant growth, but their effectiveness can vary with host species and with genotype within species. This study evaluated the effectiveness of rhizosphere microflora indigenous to the rhizosphere of switchgrass (Panicum virgatum L.) for enhancing seedling yield and nutrient uptake. Switchgrass roots and rhizosphere soil were collected from native prairies and seeded stands in Nebraska, Kansas, Iowa, Missouri, Virginia, and North Carolina. Seedlings of four switchgrass cultivars were inoculated with root fragments and rhizosphere soil from each collection, fertilized with a nutrient solution, and grown in steamed sand for 12 wk in a greenhouse. Seedlings inoculated with rhizosphere microflora produced up to 15-fold greater shoot and root yields, and recovered up to 6-fold more N and 36-fold more P than seedlings inoculated with rhizosphere bacteria only. These responses were consistent for all four switchgrass cultivars and were probably due to arbuscular mycorrhizal fungi. Switchgrass rhizosphere populations were highly variable in their ability to recover N and P and stimulate seedling shoot and root yields. Seedlings inoculated with rhizosphere populations from seeded switchgrass stands averaged 1.5-fold greater shoot and root yields than seedlings inoculated with rhizosphere populations from native prairies. Rhizosphere populations that stimulated the greatest N uptake differed from populations that resulted in the greatest P uptake. Highly effective microbial populations appear to develop in the rhizosphere of seeded switchgrass stands.

The reported research is from a dissertation submitted by the senior author (John J. Brejda) in partial fulfillment of the requirements for a Ph.D. degree at the University of Nebraska. The research was funded in part by the U.S. Dep. of Energy's Biomass Fuels program via Oak Ridge Natl. Lab., USDA-ARS, and the University of Nebraska. Contract no. DE-A105-900R21954. Joint contribution of the USDAARS and the University of Nebraska Agric. Exp. Stn. as Journal Article 11919.

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