ABSTRACT The use of no-till conservationist agricultural systems as well as intercropping in the Cerrado biome are practices that increase soil organic matter (SOM) due to the deposition of straw. This study aimed to quantify the carbon stock and organic fractions of a latosol under off-season monoculture (Sorghum bicolor and Urochloa ruziziensis) and intercropping (S. bicolor-U. ruziziensis) systems, in Rio Verde, state of Goiás, Brazil. Soil samples were collected from different layers: 0-10, 10-20 and 20-40 cm. The following variables were determined: organic carbon content, carbon stock, dry matter and fractions of organic matter (labile and mineral). The results showed that the organic fractions of the soil are modified according to the adopted management. Intercropping of S. bicolor and U. ruziziensis increased the carbon stock, with the presence of more labile organic fractions on the soil surface, while the use of U. ruziziensis enhances the production of recalcitrant organic fractions, promoting greater preservation of the soil organic matter.