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This article in SSSAJ

  1. Vol. 62 No. 1, p. 195-203
    Received: Aug 12, 1996

    * Corresponding author(s): dhuggins@soils.umn.edu
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Carbon Dynamics in Corn-Soybean Sequences as Estimated from Natural Carbon-13 Abundance

  1. D. R. Huggins ,
  2. C. E. Clapp,
  3. R. R. Allmaras,
  4. J. A. Lamb and
  5. M. F. Layese
  1. Southwest Experiment Station, Univ. of Minnesota, Lamberton, MN 56152
    USDA-ARS, Univ. of Minnesota, St. Paul, MN 55108
    Dep. of Soil, Water, and Climate, Univ. of Minnesota, St. Paul, MN 55108



Carbon flow in terrestrial ecosystems regulates partitioning between soil organic C (SOC) and atmospheric CO2. Our objectives were to assess SOC dynamics using natural 13C abundance in corn (Zea mays L., a C4 species)-soybean [Glycine max (L.) Merr., a C3 species] sequences. Fifteen treatments of continuous corn, continuous soybean, various sequences of corn and soybean, and fallow were initiated in 1981 at Lamberton, MN, on a Webster clay loam (fine-loamy, mixed, mesic Typic Haplaquoll). In 1991, soil and aboveground shoot samples from all treatments were analyzed for total organic C and δ13C. Carbon inputs, δ13C, and SOC were integrated into a two-pool model to evaluate C dynamics of corn and soybean. Total SOC was similar across all treatments after 10 yr; however, differences in soil δ13C occurred between continuous corn (δ13C = −17.2‰) and continuous soybean (δ13C = −18.2‰). Modeled C dynamics showed SOC decay rates of 0.011 yr−1 for C4-derived C and 0.007 yr−1 for C3-derived C, and humification rates of 0.16 yr−1 for corn and 0.11 yr−1 for soybean. Decay and humification rates were slightly lower than those found in other Corn Belt studies. Levels of SOC were predicted to decline an additional 7 to 18% with current C inputs from either corn or soybean, respectively. Annual C additions required for SOC maintenance averaged 5.6 Mg C ha−1, 1.4 to 2.1 times greater than previously reported estimates. Controlled variation in natural 13C abundance in corn-soybean rotations during a 10-yr period adequately traced C dynamics.

This paper is no. 971250024 of the Minnesota Agric. Exp. Stn. Journal Series.

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