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Soil Science Society of America Journal Abstract -

Water-Dispersible Soil Organic-Mineral Particles: I. Carbon and Nitrogen Distribution1


This article in SSSAJ

  1. Vol. 43 No. 2, p. 324-328
    Received: Aug 14, 1978
    Accepted: Nov 15, 1978

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  1. J. L. Young and
  2. G. Spycher2



Water-dispersible particles from six epipedons and one Bh horizon representing six different soil orders were separated into sand, silt, and clay particles, and the clay-organic particles were further fractionated by density. Organic C and N concentrations were lowest in sand, intermediate in silt, and highest in clay, but exceptions to this trend were observed and accounted for. Light clay-size, organo-mineral particles had (i) high levels of sorbed organic C; (ii) wide C/N ratios; and (iii) low amounts of alkali-extractable C. The reverse was true for heavy clay-size particles. A continuum of particle compositions existed between the density extremes which differ for different soils. The heterogeneity of clay-size particles can be explained in terms of their position within the soil fabric: Light particles evolve at the surfaces of (micro-) aggregates and are exposed to the soil biosphere, whereas heavy particles occupy intra-aggregate space shielded from the soil biosphere.

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