Results showed that microbial biomass C was significantly increased with fertilizers in both the surface and sub-surface soil as compared to the control. Maximum increase in soil microbial biomass C was observed in the plot treated with mixed application of farmyard manure and mineral fertilizers. The application of organic fertilizer (farmyard manure) and NPK might have increased the soil organic carbon (Christensen, 1988 and Courtney and Mullen, 2008) which acts as an energy source for microbes and consequently increased soil microbial biomass C (Goyal et al., 2006). Different doses of mineral fertilizers cause variable rooting depths thereby causing stratification of soil organic C (Lorenz and Lal, 2005) which explains the increase of microbial biomass C with each increment of mineral fertilizers as well as the decreasing content of soil microbial biomass C with depth. Also, the increasing soil depth resulted in an adverse soil environment, like reduced aeration and increased soil compaction (data not shown) that might have reduced soil microbes to flourish deep into the soil. Data also revealed that soil microbial biomass C decreased with increasing period of incubation. This might be due to the decreasing content of easily metabolizable components of the soil organic matter with time (N’Dayegamiye et al., 1997) followed by slow mineralization and the formation of more stable organic forms.