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This article in SSSAJ

  1. Vol. 73 No. 5, p. 1699-1706
     
    Received: July 15, 2008


    * Corresponding author(s): cimelio.bayer@ufrgs.br
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doi:10.2136/sssaj2008.0241

Building Up Organic Matter in a Subtropical Paleudult under Legume Cover-Crop-Based Rotations

  1. F. C. B. Vieiraa,
  2. C. Bayer *a,
  3. J. A. Zanattaa,
  4. J. Mielniczuka and
  5. J. Sixb
  1. a Univ. Federal do Rio Grande do Sul, C.P. 776, 90001-970 Porto Alegre (RS), Brazil
    b One Shields Ave., Dep. of Plant Sciences, Univ. of California, Davis, CA 95616-8780

Abstract

The potential of conservation management systems to ameliorate degraded agricultural soils and mitigate global warming is related to their potential for long-term stabilization of soil organic matter (SOM). This study was performed in a 19-yr-old experiment that was set up on a degraded Paleudult (220 g kg−1 clay) in southern Brazil to (i) evaluate the effect of seven no-till crop rotations (grass- and legume-based cover crop systems) and mineral N fertilization (0 and 145 kg ha−1 yr−1) on soil organic C (SOC) stocks (0–17.5-cm depth) and (ii) estimate rates of SOM dynamics in these systems under subtropical climate conditions. Annual C input (shoot + root) ranged from 2.61 to 7.84 Mg ha−1, with the highest values in legume-based and N-fertilized cropping systems. The SOC stocks were closely related to C input levels, and a minimum C input of 4.05 Mg ha−1 yr−1 was estimated to maintain the original SOC stock of 31.38 Mg ha−1 Based on the one-compartment model of SOM dynamics, the SOM decomposition rate was estimated to be 1.2% and the humification coefficient was estimated to be 9.6%. After 19 yr, the stock of the original SOC decreased to about 24.78 Mg ha−1, while accumulation of SOC derived from the crops ranged from 4.26 to 12.79 Mg ha−1 Our results highlighted the benefits of legume cover crop species in no-till systems for the stabilization of SOC in degraded agricultural soils.

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