Objective To study effects of different fertilization treatments on soil microbial number, microbial biomass carbon(MBC), microbial biomass nitrogen(MBN) and microbial biomass phosphorus(MBP).

Method Fifteen soil samples were collected from the long-term located fertilization experimental station of Shenyang Agricultural University. The effects of fertilization on microbial number and microbial biomass, and the correlation were studied using microbial culture and chloroform extraction method.

Result Fertilization had a positive effect on microbial number and microbial biomass. The most affected soil microbes were bacteria, followed by fungi and actinomycetes.The most affected microbial biomass was MBP, followed by MBN and MBC. Among 15 treatments, organic treatment M1 had the highest number of bacteria, organic treatment M2 had the highest number of actinomycetes, and M1NPK treatment combining organic and inorganic fertilizers had the highest number of fungi. M1 had the highest number of MBC and MBN, while M2NPK with organic and inorganic fertilizers had the highest number of MBP. There was a positive correlation between MBC and microbial number.

Conclusion Organic fertilizer significantly increases microbial number. Reducing inorganic fertilizer can increase MBC and MBN with organic and inorganic fertilizers. Appropriate application of nitrogen and phosphorus fertilizers can promote the microbe to absorb nitrogen and phosphorus, and significantly increase MBN and MBP. Nitrogen fertilizer application can accelerate the loss of soil fertility which causes the soil to change from bacteria type to fungi type. Organic fertilizer application can increase soil fertility.