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This article in JEQ

  1. Vol. 25 No. 4, p. 822-827
    Received: Apr 17, 1995

    * Corresponding author(s): wwood@ag.auburn.edu
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Composition and Decomposition of Soybean and Sorghum Tissues Grown under Elevated Atmospheric Carbon Dioxide

  1. F. P. Henning,
  2. C. W. Wood *,
  3. H. H. Rogers,
  4. G. B. Runion and
  5. S. A. Prior
  1. Cooperative Ext. Serv., N. Fulton Gov. Annex, Room 203, 7741 Roswell Rd, Dunwoody, GA 30350;
    Dep. of Agronomy and Soils, 202 Funchess Hall, Auburn University, AL 36849-5412;



It has been hypothesized that changes in both quantity and quality of plant residue inputs to soils as atmospheric carbon dioxide (CO2) concentration increases may alter carbon (C) and nitrogen (N) turnover rates and pool sizes. We determined the effect of elevated atmospheric CO2 on plant tissue quality, and how modifications in tissue quality affect C and N mineralization. Soybean [C3; Glycine max (L.) Merr. cv. Stonewall] and sorghum [C4; Sorghum bicolor (L.) Moen. cv. Savanna 5] were grown under elevated (704.96 ± 0.33 µmol CO2 mol−1) and ambient (357.44 ± 0.12 µmol CO2 mol−1) atmospheric CO2 in open-top chambers. Leaf and stem tissues were separated from harvested plants and analyzed for C, N, lignin, and cellulose. Tissues were applied to Norfolk loamy sand (fine-loamy, siliceous, thermic Typic Kandiudult) and aerobically incubated for 70-d to determine C and N mineralization, C turnover, relative N mineralization, and C/N mineralized. Elevated CO2 had no effect on plant residue C concentration, but N concentration of soybean leaves and stems and sorghum stems was reduced; however, CO2 enrichment increased C/N ratio and lignin concentration for only sorghum stems and soybean leaves, respectively. Source of plant residue (i.e., produced under either elevated or ambient CO2) had no impact on soil C turnover, relative N mineralization, cumulative C and N mineralization, and C/N mineralized. These data suggest that increasing atmospheric CO2 will have little effect on composition or decomposition of field crop residues. Thus, since CO2 enrichment results in increased photosynthetic C fixation, the possibility exists for increased soil C storage under field crops in an elevated CO2 world.

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