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This article in SSSAJ

  1. Vol. 75 No. 1, p. 79-91
     
    Received: Feb 28, 2009
    Published: Jan, 2011


    * Corresponding author(s): sjohnadisa@yahoo.com
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doi:10.2136/sssaj2009.0081

Carbon Fractions Associated with Silt-Size Particles in Surface and Subsurface Soil Horizons

  1. Shade John Adisa *a and
  2. Stephen Nortcliffb
  1. a Dep. of Soil Science and Land Management, College of Plant Science and Crop Production, Univ. of Agriculture, Abeokuta, P.M.B. 2240, Abeokuta, Ogun State, Nigeria
    b Dep. of Soil Science, School of Human and Environ. Science, Univ. of Reading, Whiteknights Campus, PO Box 233, Reading, RG6 6DW, UK

Abstract

Information on the distribution and behavior of C fractions in soil particle sizes is crucial for understanding C dynamics in soil. At present little is known about the behavior of the C associated with silt-size particles. We quantified the concentrations, distribution, and enrichment of total C (TC), readily oxidizable C (ROC), hot-water-extractable C (HWC), and cold-water-extractable C (CWC) fractions in coarse (63–20-μm), medium (20–6.3-μm), and fine (6.3–2-μm) silt-size subfractions and in coarse (2000–250 μm) and fine (250–63 μm) sand and clay (<2-μm) soil fractions isolated from bulk soil (<2 mm), and 2- to 4-mm aggregate-size fraction of surface (0–25 cm) and subsurface (25–55 cm) soils under different land uses. All measured C fractions varied significantly across all soil particle-size fractions. The highest C concentrations were associated with the <20-μm soil fractions and peaked in the medium (20–6.3-μm) and fine (6.3–2-μm) silt subfractions in most treatments. Carbon enrichment ratios (ERC) revealed the dual behavior of the C fractions associated with the medium silt-size fraction, demonstrating the simultaneous enrichment of TC and ROC, and the depletion of HWC and CWC fractions. The medium silt (20–6.3-μm) subfraction was identified in this study as a zone where the associated C fractions exhibit transitory qualities. Our results show that investigating subfractions within the silt-size particle fraction provides better understanding of the behavior of C fractions in this soil fraction.

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