Abstract
No-tillage (NT) practices can result in greater soil aggregation and higher soil organic matter (SOM) levels than conventional-tillage (CT) practices, but the mechanisms for these effects are poorly known. Our objectives were to describe the size and quality of biologically active pools of aggregate-associated SOM in long-term CT and NT soils of the southeastern USA. Samples were collected from replicated CT and NT plots on a Hiwassee sandy clay loam (clayey, kaolinitic, thermic Rhodic Kanhapludult) and separated into four aggregate size classes (>2000, 250–2000, 106–250, 53–106 µm) by wet sieving. Potentially mineralizable C and N and N2O emissions were measured from 20-d laboratory incuhations of intact and crushed macroaggregates (>250 µm) and intact microaggregates (