Macro-aggregate stabilization by wetting/drying cyclesand 13C-glucose

Park, E.J.  and A.J.M. Smucker

Presented at the All Scientist Meeting (2004-10-08 )

Changes in the stability of soil macro-aggregates and associated distributions of C, N and microorganisms within macro-aggregates are induced by multiple wetting/drying cycles.  We identified pore expansion processes which promote C sequestration when stable pore structures develop and promote the influx of dissolved organic C within aggregates.  Aggregates, 6.3-9.5mm across, from a long-term no tillage site of a Wooster silt loam were incubated for 35 days with no wetting/drying cycles and no glucose (Control), 5 wetting/drying cycles and no glucose (W/D), and 5 wetting/drying cycles and 250mg glucose-C/g soil (W/D+G).  Aggregate stability decreased with W/D cycles but could be recovered with additions of glucose.  It appears that larger quantities of C respired from  exterior layers of aggregates than from interior regions and more glucose diffused into interior regions of aggregates by W/D cycles.  Changes in spatial distributions of microorganisms and promoted porosities within aggregates are being analyzed for each treatment.

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