The present study evaluates the effect of increasing rates of mineral nitrogen (90; 120; 150 kg×ha-1), liquid manure (80 t×ha-1) and solid manure (45 t×ha-1) on the microbial properties of vertisol (total number of microorganisms, numbers of actinomycetes and cellulolytic microorganisms) under maize. The research results showed dependence of the number of the test groups of microorganisms on the type and rate of fertilization, as well as on the date and zone of sampling. Namely, lower nitrogen fertilization rates (90 and 120 kg×ha-1) induced a significant increase in the total number of microorganisms, whereas the high rate (150 kg×ha-1) had a depressive effect, especially in maize edaphosphere. However, the numbers of actinomycetes and cellulolytic microorganisms were not reduced under these treatments. The organic fertilizers applied had a stimulatory effect on the above soil biological parameters.