A long-term trial sited in Saria, Burkina Faso, under Sudano-Sahelian conditions was used to assess the effect of organic and inorganic fertilization on Soil Organic Matter (SOM) fractions and sorghum performance. Sorghum straw and kraal manure were applied yearly at 10 t ha-1, with and without 60 kg of urea N ha-1. The other treatments included a control (no fertilization), only inorganic fertilization (60 kg of urea N ha-1) and fallowing. The long-term application of organic resources of varying C/N ratio and urea resulted into different SOM concentrations. Twenty years of continuous cultivation without external inputs (the control treatment) depleted SOM levels to below 50% of those under fallow. Sole urea application further depleted SOM status, presumably because of alleviation of nitrogen limitations to decomposition. SOM depletion as compared to the fallow treatment seemed less pronounced in case of application of organic material with a relatively low C/N ratio such as manure. The adverse effect on soil organic matter and nitrogen status mostly affected the fraction of SOM > 0.053mm (Particulate Organic Matter, POM). The POM concentrations in the control, straw and urea-only plots were about one-half of the POM concentrations in the fallow plots. POM concentrations increased in the following order: urea < control < straw with or without urea < manure with or without urea < fallow. The fraction of SOM < 0.053mm (fine organic matter, FOM) was greater than POM in all plots except in fallow and manure + urea plots. Total nitrogen concentration followed the same trend as soil organic matter, but cultivation led to a decline in both POM-N and FOM-N. Crop yield was greatest in the manure plots and lowest in the straw, control and urea only plots. Results indicate that under Sudano-Sahelian conditions, SOM, POM and FOM fractions, fertilizer recovery fraction and crop performance were better maintained using organic resources with a low C/N ratio (manure) than through organic materiel with a relatively high C/N ratio (straw). Urea improved the effect of the organic material with high C/N ratio (straw) on crop yield and SOM concentration.