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This article in SSSAJ

  1. Vol. 70 No. 4, p. 1398-1406
    Received: Sept 21, 2005

    * Corresponding author(s): stuart.grandy@colorado.edu


Aggregation and Organic Matter Protection Following Tillage of a Previously Uncultivated Soil

  1. A. Stuart Grandy * and
  2. G. Philip Robertson
  1. W.K. Kellogg Biological Station and Dep. of Crop and Soil Sciences, Michigan State Univ., Hickory Corners, MI 49060. A.S. Grandy currently at: University of Colorado–Boulder, Dep. of Geological Sciences, Boulder, CO 80309-0399


Understanding the effects of tillage on soils following years or decades of no-till is critical for developing C conservation strategies. To date, short-term responses to tillage in previously uncultivated or other long-term no-till soils have primarily focused on total C changes, which are difficult to detect. Tillage effects on soil conservation and C permanence may be better predicted by changes in more readily detected factors known to affect C storage such as aggregation and physically protected C. We annually plowed replicated plots in a previously uncultivated midsuccessional field between 2002 and 2004 and investigated changes in the distribution of aggregates, physically protected C, and light fraction (LF) organic matter. Within 60 d of initial cultivation, soil aggregates in the 2000- to 8000-μm size class declined from 0.47 to 0.15 g g−1 at 0- to 7-cm soil depth and from 0.32 to 0.23 g g−1 at 7 to 20 cm. Lower levels of aggregation persisted through the winter and spring of the following year. Inter-aggregate, unprotected light fraction (LF) increased following cultivation, as did particulate C in soil fractions with densities < 1.9 g cm−3 Changes in the mass of total soil C were not detectable after 3 yr but the vertical distribution of all soil C pools was altered by plowing. Our study demonstrates that plowing once immediately and substantially alters aggregation and LF and particulate C dynamics and that these conditions persist. Results suggest that no-till soils need to be continuously maintained to protect aggregation and physically stabilized C pools.

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