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This article in JEQ

  1. Vol. 35 No. 4, p. 1470-1477
     
    Received: Apr 30, 2005
    Published: July, 2006


    * Corresponding author(s): sprior@acesag.auburn.edu
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doi:10.2134/jeq2005.0163

Free-Air Carbon Dioxide Enrichment of Soybean

  1. S. A. Prior *a,
  2. H. A. Torberta,
  3. G. B. Runiona,
  4. H. H. Rogersa,
  5. D. R. Ortb and
  6. R. L. Nelsonc
  1. a USDA-ARS National Soil Dynamics Laboratory, 411 South Donahue Drive, Auburn, AL 36832
    b USDA-ARS Photosynthesis Research Unit, 1201 West Gregory Drive, Urbana, IL 61801
    c USDA-ARS, 232 National Soybean Research Center, 1101 West Peabody Drive, Urbana, IL 61801

Abstract

Elevated atmospheric CO2 can result in larger plants returning greater amounts of residue to the soil. However, the effects of elevated CO2 on carbon (C) and nitrogen (N) cycling for different soybean varieties have not been examined. Aboveground residue of eight soybean [Glycine max (L.) Merr.] varieties was collected from a field study where crops had been grown under two different atmospheric CO2 levels [370 μmol mol−1 (ambient) and 550 μmol mol−1 (free-air carbon dioxide enrichment, FACE)]. Senesced residue material was used in a 60-d laboratory incubation study to evaluate potential C and N mineralization. In addition to assessing the overall effects of CO2 level and variety, a few specific variety comparisons were also made. Across varieties, overall residue N concentration was increased by FACE, but residue C concentration was only slightly increased. Overall residue C to N ratio was lower under FACE and total mineralized N was increased by FACE, suggesting that increased N2 fixation impacted residue decomposition; total mineralized C was also slightly increased by FACE. Across CO2 levels, varietal differences were also observed with the oldest variety having the lowest residue N concentration and highest residue C to N ratio; mineralized N was lowest in the oldest variety, illustrating the influence of high residue C to N ratio. It appears (based on our few specific varietal comparisons) that the breeding selection process may have resulted in some varietal differences in residue quality which can result in increased N or C mineralization under elevated CO2 conditions. This limited number of varietal comparisons indicated that more work investigating varietal influences on soil C and N cycling under elevated CO2 conditions is required.

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