Moldboard plowing effects on soil aggregation and soil organic matter quality assessed by 13 C CPMAS NMR and biochemical analyses. M. Panettieri a* , H. Knicker a , A.E. Berns b , J.M. Murillo a and E. Madejón a . a Instituto de Recursos Naturales y Agrobiología de Sevilla, IRNAS-CSIC. PoBox 1052, 41080 Sevilla, Spain. b Institute of Bio- and Geosciences - Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Strasse, 52425 Jülich, Germany. * Corresponding author. Phone: +34 954624711; fax: +34 954624711; E-mail addresses: marco.panettieri@csic.es Abstract The impact on soil aggregates status of two tillage practices (moldboard plowing, TT, and chisel plowing, RT) applied to a farm previously cultivated under no-tillage (NT) was studied. The edžperiŵeŶt ǁas Đarried out oŶ a LeptiĐ TLJpiĐ XerortheŶt soil at the Las Naǀas drLJlaŶd experimental farm located in Jerez de la Frontera (Cadiz, SW Spain). Several organic C pools such as total organic carbon (TOC), water soluble carbon (WSC), permanganate oxidizable carbon (POxC), and microbial biomass carbon (MBC) were analyzed, together with two enzymatic activities related to soil organic matter (SOM) oxidization metabolism: dehLJdrogeŶase aĐtiǀitLJ ;DHͿ aŶd β-GluĐosidase aĐtiǀitLJ ;β-Glu). 13 C cross polarization magic angle spinning nuclear magnetic resonance ( 13 C CPMAS NMR) spectroscopy was used to characterize the composition of the SOM and its degradation status. Two years after the implementation of the new management practices, analysis of the aggregate distribution of