A major part of Iran has been covered by arid to semiarid climate. Sixty percent of the soils of the country possess less than 1% of organic matter thereby; both growers and researchers have paid considerable attention to organic amendments. Application of municipal solid wastes, sewage sludge, animal manure and crop residues are predominant management practices by which soil organic carbon are conserved and nutrients would be replenished. Vermicomposting as well as composting are highly recommended procedures that are widely used for producing organic amendments. Eisenia foetida an epigeic earthworm belongs to the family Lumbericideae consumes some of the proper solid wastes and convert them to a dark colored, enriched in nutrients and stable organic amendment that is named vermicompost. The aim of the present study was to: 1) identify the temporal changes of amidohydrolases and soluble organic N (SON) during vermicomposting process and 2) investigate the decomposability of the vermicomposts with varying degree of maturity in two soils of contrasting properties. The vermicompost was non-destructively sampled at seven sampling times with 10 days interval (T0, T1, T2, T3, T4, T5 and T6). The sampling time T0 belongs to the start of the vermicomposting process when the worms were not still added to the organic materials. The vermicomposting process performed on the two solid wastes including cow manure and wheat residue. The urease, L-glutaminase and L-asparaginase activities along with soluble organic N (SON) and total inorganic N (TIN) were assayed at each sampling time. In the second experiment, the vermicomposts produced in the first experiment were added separately to two calcareous and acid soils at the rate of 1 g C kg -1 soil and the evolved carbon dioxide were measured periodically in 45 days of incubation under optimum moisture and aerobic condition at 25 °C. A randomized complete block design with a factorial arrangement was used for both of the experiments. In the first experiment we observed that urease activity decreased significantly as the vermicomposting of the cow manure and wheat residues proceeded. The urease activity in the cow manure vermicomposts was negatively correlated with lignine content (r = -0.88**) and pH (r = 0.92**) and was positively correlated with C:N ratio (r = 0.90**). L-glutaminase and L-asparaginase behaved differently, as they increased in an early period (before T4) and then remained unaffected until the end of the experiment. The activity of L-glutaminase and L-asparaginase in the samples of varying degrees maturity were highly correlated (r = 0.91**). A decreasing trend was monitored in the soluble organic N during vermicomposting while a contrasting trend was observed for the total inorganic N. Simple correlation studies revealed that SON and TIN are negatively correlated (r = -0.88**). In the second experiment, it was observed that the evolution of the carbon dioxide conformed well to a first-order kinetic model. The greatest amounts of CO 2 evolved, were observed in the early 7 days in all treatments. The cumulative CO 2 evolved was increased decreasingly until the end of the incubation. Higher values of potentially mineralizable C (C 0 ) was observed in the wheat residue vermicomposts. The decomposability of the vermicomposts by varying maturity was explained alternatively by potentially mineralizable C (C 0 ) and the initial potential rates (kC 0 ). Key words : vermicompost, Eisenia foetida , cow manure, wheat residue, enzyme activities, soluble organic N, decomposability