Abstract : Conventional practices of soil management, by degrading soil attributes, have been questioned. In this context, soil management systems with conservationist bases that use permanent soil coverage allied to succession or crop rotation maintain or improve these attributes. The objective of this study was to evaluate the influence of different species of cover plants in onion systems under succession or crop rotation on chemical attributes and soil organic matter fractions (SOM) in soil aggregates and in dry fine soil at air (bulk soil). The experiment was implemented in April 2007 in a Humic Cambisol, in Ituporanga, Santa Catarina (SC), with eight treatments: succession of onion and maize in no-tillage system (NTS) (T1); rotation of soil cover plants (winter), and biennial onion in NTS (T2); rotation of maize, winter grasses, and annual onion in NTS (T3); succession of velvet bean, and annual onion in NTS (T4); rotation of millet, soil cover plants (winter), and annual onion in NTS (T5); succession of velvet bean, rye, and annual onion in NTS (T6); succession of maize, and onion in conventional tillage system - CTS (T7); succession of intercrops of soil cover plants (summer), and annual onion in NTS (T8). In July 2014, undisturbed soil samples were collected in the 0-5, 5-10 and 10-20 cm layers. From these samples, the soil aggregates and the bulk soil were obtained. The total organic carbon (TOC), total nitrogen (TN), soil chemical attributes and the granulometric fractionation of the SOM was quantified. Periodic soil turning (CTS) in the succession of maize, and onion (T7) reduces TOC, particulate organic carbon (POC), organic carbon associated with minerals (OCam), TN, particulate nitrogen (PN), nitrogen associated with minerals (Nam) both in the aggregates and the TFSA when compared to NTS with the use of cover plants in succession and crop rotation with onion. The use of velvet bean and rye in succession increased in general the contents of TOC, TN, K, P, POC, OCam PN, Nam both in the aggregates and bulk soil when compared to the sequence with only grasses or only legumes. The use of cover crops of different botanical families, mainly intercrops of soil cover plants summer, and succession of legumes in summer and grasses in winter, in general, increased the chemical attributes of the soil and SOM both in the aggregates and bulk soil. In general, higher values of TOC, TN, POC, PN, Ca and K were observed in bulk soil when compared to soil aggregates. In the soil aggregates, higher soil acidity indexes were observed, with lower pH values, higher H + Al and Al, higher P and Mg values compared to bulk soil. The main changes resulting from the management systems adopted and the use of the different combinations of cover plants used were observed through the analysis of particulate organic matter, mainly in the soil aggregates.