Biogeochemical processesstabilizing soil aggregates from agriculturalecosystems

Park, E.J., H.A. Dopp, and A.J.M. Smucker

Presented at the All Scientist Meeting (2003-09-12 )

Stable soil aggregates preserve intra-aggregate porosities that do not collapse during wetting and drying cycles. Stable micropore networks increase the retention of carbon which feeds back into the formation of more stable aggregates. We investigated aggregate stability by wet sieving and by polar tensile strength crushing resistances of aggregates from agricultural ecosystems in two Hoytville and Wooster soil series. Carbon contents, textural distributions, and intra-aggregate porosities were compared. Soil carbon contents in aggregates from no tillage (NT) systems were 1.6 and 2.2 fold greater than conventional tillage (CT) systems from Hoytville and Wooster, respectively. Water stability of soil aggregates increased with increasing C content and became most stable as C contents exceeded 4%. C content and water stability of aggregates showed positive correlations with intra-aggregate porosities that decreased by 6-7% in CT aggregates. Polar tensile strength of dry aggregates increased with increasing bulk density, C, and clay content. These results suggest that non-disrupted and higher intra-aggregate porosities retained more internal carbon. This is indirect evidence of accelerated organo-clay mineral interactions.

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