A field experiment was conducted to study the effects by match fertilizer N and P on microbial biomass C and N of black soil agroecosystem. The result of the variation of microbial biomass in different growth periods shows that the effects of fertilizer N and P on microbial biomass C is not same as on microbial biomass N

incubation period is the most obviously varied period of microbial biomass C and N

the microbial biomass C is at its lowest but microbial biomass N is at its highest.The regression analysis indicated that fertilizer N is the main factor in affecting the microbial biomass C

It showed that the excessive use of fertilizer N decrease the content of microbial biomass N

and fertilizer P can increase the content of microbial biomass N though it was applied property or excessive

the effect decrease follow the increase of use the fertilizer P. The match of fertilize N and P can increase the microbial biomass N

so we can say that it is not a effective way in increase the quantity of microbial biomass N by applying fertilizer N or fertilizer P singly

the effective way to increase soil microbial biomass N is by match applying of N and P