The purpose of the study was to assess the consequences of long-term tillage and crop rotation systems on soil organic carbon sequestration with special emphasis on related aggregate stability. Organic carbon (OC) content, bulk density (BD), water-retention (volumetric and gravimetric) and aggregate stability (by wet sieving for macroaggregates and rheology for microaggregates) were determined on a dark Chalmers silty clay loam in a long-term (28-year) crop rotation and tillage experiment. Soil samples were taken to 30 cm depth in three depth increments. Macroaggregate stability was significantly influenced by tillage, rotation and their interaction at certain depths. Macroaggregate stability was consistently higher in no-till than in plow and continuous corn had higher mean weight diameter than the soybean-corn rotation in all depth increments. Water retention was influenced by tillage but not by rotation; tillage × rotation interactions were not significant. The rheological measurements supported our findings by wet sieving.
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