Abstract:Based on a field study of the aquic brown soil in the suburbs of Shenyang City in Northeast China over a consecutive 19 years, the effects of fertilization and soil management on the microbial biomass (C and N) and communities were investigated. The results showed that microbial biomass of the bare land and farmland was low. Fertilization increased the microbial biomass, especially when mineral fertilizers and pig manure (NPK+M) were applied. DGGE fingerprinting indicated a high similarity in the distribution of most bacterial bands among all treatments, and the bacterial diversity of the bare land was the highest. There were significant variations of fungal community structure among different treatments. Long-term fertilization increased fungal diversity and manure was more effective than mineral fertilizer to increase fungal diversity. Long-tem fertilization and soil management had a large effect on the ammonia-oxidizing bacteria structure in soil. Moreover, manure and mineral fertilizer influenced the ammonia-oxidizing bacterial communities in different ways. When applied together NPK+M increased the diversity most significantly. On the contrary, fertilization and soil management had less effect on the bacterial communities. Cluster analysis suggested that soil management practice had a larger effect on the community structures of bacteria, fungi and ammonia-oxidizing bacteria than fertilization.