A meta-analysis approach to assess the effects of fertilizations on soil microbial biomass in China's farmlands

Aimed at providing a scientific basis for formulating reasonable farmland management policy, safeguarding national food security and mitigating climate change, we integrated to analyze the variation characteristics of soil microbial biomass under different fertilizations.We collected the data from published literatures in 1990-2015, and used a meta-analysis approach to quantify the effects of fertilizations(chemical fertilizers and organic manure) on the content of soil microbial biomass carbon (SMBC) and nitrogen (SMBN) with different spatial distribution, experimental duration and inherent soil properties (e.g., texture).Compared with no fertilization (CK), fertilizations significantly increased SMBC and SMBN contents.Different fertilizations showed spatial differentiation in tillage layer; especially in northwest China, combined application of organic manure and chemical fertilizers significantly increased more SMBC and SMBN contents than those in northeast and southeast China.Significantly, loam soil with organic manure application was with more SMBC and SMBN contents than those of clay, silt-loam and sandy-loam soils.Therefore, organic manure application (addition or combination) would significantly sustain and improve soil organic carbon and fertility in northwest China or other low soil fertility areas.